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Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic plasticity

Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic... !"# Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic plasticity 1,2 1 V. S. Uieda and T. L. F. Pinto Department of Zoology, UNESP – Univ Estadual Paulista, C.P. 510, 18618-970. Botucatu, SP, Brazil Corresponding author. Fax: 55-14-38116052, Email: [email protected] Keywords: Benthic fauna, Electivity, Fish, Food resources, Partitioning of food. Abstract: In studies on the partitioning of resources, one issue which has been largely neglected is the change in feeding habits based on the availability of food in the environment, an aspect which is dealt with here with regard to the ichthyofauna of a tropical stream. Feeding preference was analyzed for eight species of fish which consumed high percentages of aquatic insects, based on a collection of fish and invertebrates during both the dry season (June 2006) and the wet season (December 2006) and in two different stretches of the stream, one of which shaded by gallery forest (“closed area”) and the other just bordered by herbaceous vegetation (“open area”). Based on a quantitative analysis of the composition of the benthic fauna and the diet of the ichthyofauna, the electivity index was calculated in order to assess potential alterations in the feeding preferences in line with seasonal and spatial modifications to the structure of the habitat and the supply of food. The analysis of the abundance of aquatic insects in the environment showed a predominance of Ephemeroptera in all situations analyzed (areas and seasons), with this insect group being the food item preferred by the majority of fish. However, space-time variations were observed in prey selection by the ichthyofauna. The analysis of supply, consumption and preference demonstrated somewhat varied situ- ations for the majority of species, with both high and low selectivity for items consumed in low and high percentages, with the preferred item varying both spatially and seasonally. The sole exception to this was Phalloceros harpagos, choosing Diptera- Chironomidae in all the situations analyzed. Nomenclature: Reis et al. (2003) for fishes, Fernández and Domínguez (2001) for macroinvertebrates. Abbreviations: Aboc – Astyanax bockmanni, Bihe – Bryconamericus iheringi, Cihe – Cetopsorhamdia iheringi, Ibor – Im- parfinis borodini, Imir – Imparfinis mirini, Pten – Phenacorhamdia tenebrosa, Tbra – Trichomycterus brasiliensis, Phar – Phalloceros harpagos, C – Coleoptera, D – Diptera, E – Ephemeroptera, H – Heteroptera, L – Lepidoptera, M – Megaloptera, O – Odonata, P – Plecoptera, T – Trichoptera. In lotic environments, the high availability of juvenile Introduction aquatic insects makes this resource an important source of One issue which has been somewhat overlooked in stud- food for the ichthyofauna. Seasonally, aquatic insect fauna ies on the partitioning of resources is the change in feeding may undergo alterations in composition and abundance in habits, based on the availability of food, and changes in the line with alterations in the environment’s physical stability. choice of food based on quality (Esteves and Aranha 1999). In neotropical regions, the greater environmental stability in According to Zavala-Camin (1996), selectivity or choice of the dry season may ensure a larger supply of aquatic insects food cannot be solely determined by the fact of its presence (Oliveira et al. 1997, Kikuchi and Uieda, 1998, Huamantinco in the digestive contents of the fish, since it may have been and Nessimian 1999), while an increase in flow in wet season ingested, not because it was the preferred food, but because may directly remove the fauna or its food resources (Death it was the most widely available. On the other hand, a par- and Zimmermann 2005). In spatial terms, the presence of ticular food item may be selected on account of it being more gallery forests may affect the physical structure of the stream, palatable, or because it is larger or has a higher nutritional the supply of resources (Barrella et al. 2001, Lima and Zakia value and this qualitative selection of food may vary ontoge- 2001) and, consequently, the trophic organization of the netically, though it tends to be uniform amongst individuals communities (Uieda and Motta 2007). of the same species and size (Zavala-Camin 1996). Accordingly, information concerning the usage of food It is also important to remember that the selection of food is extremely important since, as well as propitiating an inter- resources in nature may be related to their availability in the esting field for the discussion of theoretical aspects, such as environment or to the active choice of specific food items by species substitution by means of the spatial, temporal and tro- predators, according to their needs (Zavala-Camin 1996). phic components in the niche (Schoener 1974), it serves Space-time factors may also have an influence on the supply other purposes such as the basic knowledge of the biology of of food as a consequence of physical changes in the environ- the species and the understanding of the trophic organization ment and may therefore alter the feeding preference. of the ecosystem (Esteves and Aranha 1999). 32 Uieda and Pinto In the present study, the fish community of a tropical moving upriver and covering the whole length of the stretch stream was studied with the aim of establishing possible al- being studied, in both areas. terations in feeding selectivity based on two gradients, sea- In the laboratory, the sampled aquatic insects were sorted sonal (dry and wet seasons) and spatial (presence or absence using stereomicroscopy and were identified using the general of gallery forest). The influence of these gradients was ana- keys of Lopretto and Tell (1995), Merritt and Cummins lyzed with regard to both the diet of ichthyofauna and the (1996) and Fernández and Domínguez (2001), but also spe- supply of food. As aquatic insects comprise the main element cific keys for certain groups. The fish taxonomic identifica- of the benthic macrofauna in this stream (Pinto and Uieda tion was checked by Dr. Francisco Langeani and the vouch- 2007), serving as a food resource for the majority of fish spe- ers are deposited in his fish collection, located in the cies present, the feeding preference was analyzed for the spe- Department of Zoology, UNESP – Univ Estadual Paulista, cies which consumed high percentages of this important food São José do Rio Preto, Brazil (DZSJRP010101 to resource. DZSJRP010117) (http://splink.cria. org.br/manager/de- tail?resource=DZSJRP-Pisces&setlang=pt). Materials and methods The determination of the fishes’ diet was conducted by analyzing the stomach contents. The Index of Relative Im- Study area portance (IRI) was calculated using the formula of Pinkas et The study was carried out at the Ribeirão da Quinta, a al. (1971): IRI = (N + V)× F, where N = the number of indi- third-order stream located in the southeast of Brazil, at an al- viduals of each insect group present in the stomach contents expressed as a percentage of the total number of individuals titude of 743 m (23 06’47"S, 48 29’46"W). This stream is part of the Paranapanema River basin and is located on cat- from all groups (numeric method, as Hyslop 1980), V = ratio tle-raising farms far away from urban areas. Two consecutive between the area occupied by a particular item and the total area occupied by all items, the area being calculated using a areas of the Ribeirão da Quinta were used for the study: one bounded by gallery forest (closed area, upstream) while the millimeter-scale plate (biovolume method, adapted from other includes treeless riverbanks (open area, downstream). Esteves and Galetti Jr. 1995), F = frequency of the item, cal- culated using the number of fish in which the food item oc- A detailed description of the type of vegetation presents there can be found in Carvalho and Uieda (2009). curred in proportion to the total occurrences of all items (fre- quency of occurrence method, as Hyslop 1980). Alternating riffles, rapids and pools can be found in both areas, with the rapids comprising the longer stretches. Al- In order to permit a comparison of diet between the dif- though the two areas have a similar substrate in terms of com- ferent species of fish, or for the same species in different ar- position and granulometry (pebbles approximately 3 cm in eas and seasons, the IRI values were transformed into relative diameter, associated with a large quantity of vegetal debris), values (%). they differ with regard to the presence of macrophytes, which Prey selectivity was calculated for each species of fish are completely absent in the closed area while in the open using the electivity index (Ivlev 1961): E = (r -P )/(r +P ), area they populate the banks and the riverbed in large quan- in which E = electivity index, r = percentage of each item in tities (predominantly Cyperaceae). The length analyzed in the stomach contents (IRI %), P = percentage of each item the closed area (24 and 17 m in the June and December col- in the environment (relative abundance). The index values lections, respectively) also differed from the open area range from -1 to +1, where a value of zero indicates null se- (lengths of 20 and 16 m per respective collection) in terms of lectivity, results <0 indicate negative selection for the item the mean values for current speed (0.24 and 0.33 m.s , in the and those values >0 denote positive selection (Zavala-Camin closed and open areas respectively), depth (0.13 and 0.22 m) 1996, Harrison et al. 2005). For the purposes of the present and width (3.2 and 1.1 m). study, a selectivity value greater than or equal to 0.5 was con- sidered to be high. The selectivity values showed in the fig- Sampling and data analysis ures and referred in the text corresponded to a mean of the index values calculated for all fish individuals of each fish The sampling of aquatic insects and fish were carried out species. These values were used to analyze the similarity in stretches of rapids in the two areas (closed and open) and (group average clustering with Euclidean distance) between in two seasons of the year (June 2006 – dry season, and De- the diet of species sampled in the two areas and seasons, and cember 2006 – wet season). The benthic macroinvertebrates also Principal Components Analysis to determine the contri- were sampled using a Surber net (900 cm ; mesh 0.250 mm) bution of each insect order to this similarity (Primer v.6; in a total of 10 replications per area and per season. For the Clarke and Gorley 2006). sampling of ichthyofauna a gill net was used (2 mm plastic mesh) and the catching effort was standardized (4 collectors, Results 2 hours per area). The net was settled transversely to the river, bridging the two banks, with the substrate in front of the net being stirred up by feet and hands in order to dislodge A total of ten species of fish were collected at Ribeirão the fish, which were subsequently transported by the current da Quinta, but only two Loricariidae species - Hisonotus de- into the net. The sampling was conducted at intervals of 2 m, pressicauda (Miranda Ribeiro, 1918) and Hypostomus ni- Feeding selectivity of ichthyofauna in a tropical stream 33 ! " #$ % & & ! ’ ( & Trichoptera families (Leptoceridae and Polycentropodidae) gromaculatus (Schubart,1964) – consumed mainly periphy- stood out as having high selectivity, though with low con- ton (more than 75% of the food ingested). For the other eight sumption. species (Table 1) aquatic insects were the main food item in- gested. Five of these species corresponded to small catfish, With regard to B. iheringi, it was possible to ascertain of which four belong to the Heptapteridae family - Cetop- spatial and seasonal differences in diet (Fig. A1 in Appen- sorhamdia iheringi Vari & Castro, 2007; Imparfinis borodini dix). In the open area-dry season, this species consumed a Mees & Cala, 1989; Imparfinis mirini Haseman, 1911; Phen- high percentage and presented positive selectivity for Ephe- acorhamdia tenebrosa (Schubart, 1964) – and one to the meroptera-Leptophlebiidae (Fig. A1a, Table A1). In spite of Trichomycteridae family - Trichomycterus brasiliensis Lut- the negative selectivity values for the other orders, high posi- ken, 1874. The species Phalloceros harpagos Lucinda, 2008 tive selectivity was found for a family of Coleoptera – Poeciliidae was the only species sampled in the closed area (Psephenidae) consumed in low percentage. On the other during the dry season. The other two species belong to the hand, also in this area, but in the wet season (Fig. A1b), this Characidae family – Astyanax bockmani Vari & Castro, 2007 species presented negative electivity values for all orders of insects consumed, despite the high-positive electivity values and Bryconamericus iheringi (Boulenger, 1887). for Coleoptera-Psephenidae, consumed in high percentage, The analysis of abundance of aquatic insects in the envi- and for a further five families, within the orders Lepidoptera, ronment showed a predominance of Ephemeroptera in all the Odonata and Trichoptera, with low consumption (Table A1). situations analyzed (Table 1), with the few differences found In the closed area, this species only occurred in the wet sea- between areas and seasons relating to the second and/or third son, when it consumed a larger percentage and presented most abundant groups, although in this case they always var- positive selectivity for Lepidoptera and Trichoptera (Fig. ied between Diptera, Trichoptera and Coleoptera, in roughly A1c). However, when analyzed at the family level, the highest equal proportions. Despite this similarity in the existing re- selectivity values stood out for Coleoptera-Curculionidae, sources, it was possible to ascertain spatial and time differ- Plecoptera-Perlidae and Lepidoptera-Pyralidae (Table A2). ences in terms of consumption and feeding selectivity by the ichthyofauna (Fig. 1, Figs. A1 to A7 in Appendix). Occurring only in the wet season in the two areas, C. iheringi presented an apparent spatial variation in diet, in the In the open area-dry season, the species A. bockmanni open area consuming in high percentage and with high-posi- presented a larger consumption and positive selectivity for tive selectivity for Plecoptera-Perlidae and Diptera-Simulii- Diptera and Trichoptera (Fig. 1a), with a high electivity in- dae (Fig. A2a, Table A1 in Appendix), while in the closed area dex value for Diptera-Chironomidae, consumed in high per- it consumed a high percentage and presented a high value of se- centage, and for two families of Trichoptera (Hydroptilidae lectivity for Diptera-Chironomidae (Fig. A2b, Table A2). and Leptoceridae), consumed in low percentages (Table A1 in Appendix). As for the remaining insect groups, A. bock- As for I. borodini, it was also possible to ascertain spatial manni presented negative selectivity values. However, when and seasonal differences in the diet (Fig. A3 in Appendix). analyzing the diet of this species in the wet season, a greater Despite the individuals of this species of catfish captured in consumption and a high-positive selectivity was observed for the open area having consumed a high percentage of Ephe- Ephemeroptera (Fig. 1b), mainly Baetidae (Table A1). Also meroptera in both seasons, it only presented high and posi- in the wet season, despite A. bockmanni having presented tive values of selectivity for this order in the wet season (Figs. negative selectivity for the other orders of insects, on analyz- A3b). In addition, in the dry season, when analyzed at the ing the families, one Diptera (Ceratopogonidae) and two family level (Table A1), it was highly selective for Ephe- 34 Uieda and Pinto ) & & * & ’ ( & ’ - ./ & ’ . ( 0’ / & & ) 1 & * + + ’ tera-Leptophlebiidae, Trichoptera-Hydroptilidae and meroptera-Baetidae and for two families of Trichoptera Trichoptera-Philopotamidae (Fig. A5, Table A1 in Appen- (Glossosomatidae and Hydropsychidae), the second most dix). consumed in percentage terms similar to that of the Baetidae, whereas in the wet season it presented high-positive selectiv- As for T. brasiliensis, spatial and seasonal differences ity for Ephemeroptera-Leptophlebiidae, Lepidoptera-Pyrali- were also noted in the diet (Fig. A6). In the open area, in both seasons, this species consumed a high percentage and pre- dae and Diptera-Simuliidae, with only the first mentioned having a high percentage of consumption (Table A1). In the sented high, positive selectivity for Ephemeroptera, though closed area-wet season, I. borodini presented a high con- with higher IRI and E values for Baetidae in the dry season and for Leptophlebiidae in the wet season (Table A1). The sumption of Coleoptera and Trichoptera, but positive selec- tivity only in the case of the former (Fig. A3c). However, specimens of T. brasiliensis collected in the closed area-wet when analyzing the families, high values of positive selectiv- season consumed the most in percentage terms and presented high-positive selectivity for Diptera and Trichoptera (Fig. ity were observed, both for three Coleoptera families (Dryopidae, Elmidae and Psephenidae) and for Trichoptera- A6c). However, at the family level, high-positive selectivity Hydroptilidae, consumed in a similar percentage to that of was detected only for Diptera-Chironomidae (Table A2). In the latter two families of Coleoptera (Table A2). this case, the high consumption of Trichoptera relates to ju- veniles that could not be identified at the family level. As for the other two species of Heptapteridae, in spite of the fact that only one specimen of each was analyzed, it was With regard to P. harpagos, as well as being the species possible to detect a tendency towards a more specialized diet with the largest number of specimens studied, it was the only for I. mirini, with high consumption and high-positive selec- one collected in all the situations analyzed. This species pre- tivity for Ephemeroptera-Baetidae (Fig. A4, Table A1 in Ap- sented quite a uniform diet, both spatially and temporally, pendix).. On the other hand, P. tenebrosa consumed in high consuming in a high percentage and with high-positive selec- percentage and presented positive selectivity for Ephemerop- tivity for Diptera-Chironomidae (Fig. A7, Tables A1 and A2 Feeding selectivity of ichthyofauna in a tropical stream 35 & 3 1 tera order for the formation of Group II (negative quadrant of ’ & & PC2 axis), and of Diptera order for the formation of Group & & III (positive quadrant of PC2 axis). Discussion Fish communities in neotropical streams present a great diversity of feeding habits and tactics, thus reflecting the in- credible variety of available aquatic organisms as potential prey (Keenleyside 1979). For the families of species of fish collected from Ribeirão da Quinta, different feeding strate- gies have been recognized (Casatti et al. 2001, Casatti and Castro 2006): the family Characidae brings together species of nektonic fish which collect items of food dragged along by the current; the species of Poeciliidae family prefers to sur- vive in the backwaters and catches its prey on the surface; the small catfish of Heptapteridae and Trichomycteridae fami- lies are predominantly benthic species that hunt aquatic in- sects while inspecting the substrate. The capture technique is associated with the type of food, with no special technique being required for capturing vege- tal materials, which require suitable morphological struc- tures (Keenleyside 1979). On the other hand, for capturing moving organisms, behavioral and structural adaptations re- lating to predator-prey interaction are required (Keenleyside 1979). The large supply of these moving organisms, represented in the stream by juvenile aquatic insects, makes this resource an important item in the fish’s diet. According to Wallace and & 3 1 4 Anderson (1996), the great success of aquatic insects in the 315 31+ ’ & ’ / continental environment may be demonstrated by their diver- & & ) 1 sity, abundance, wide distribution and ability to inhabit di- & + verse types of environments. In the present study, some 2 6 & & groups were conspicuous for their high abundance, such as & " the orders Ephemeroptera, Diptera, Trichoptera and Coleop- ’ & 4 & & 6 5 tera, found in a broad diversity of situations, such as pools and riffles, rock and leaf substrates, and in great diversity of lotic environments, as second and third-order streams (Costa and Ide 2006, Calor 2007, Silva 2007, Pinho 2008). in Appendix). Only in the open area-wet season, P. harpagos also presented high selectivity for Diptera-Ceratopogonidae, These high levels of variety and abundance of food rep- despite the low consumption (Table A1). resented by aquatic insects, along with the use of different The analysis of similarity based on the electivity index feeding tactics by the ichthyofauna studied, help with the calculated for the insect orders consumed by the eight fish feeding selection or preference, which can be defined as a species (Fig. 2) reinforced this spatial and seasonal diet simi- behavior that determines the choice of the food best suited to larity for P. harpagos. The dendrogram also showed the ex- the needs of the fish (Zavala-Camin 1996). In order to calcu- istence of three major groups of cases (species/area/season) late this preference, the literature contains different electivity with positive electivity index occurring for: Coleoptera, indices that correlate the food item available in the environ- Lepidoptera and Trichoptera (Group I), for Ephemeroptera ment with the item ingested by the fish, with particular men- (Group II), and for Diptera (Group III). Except for P. har- tion for the indices of Shorigin (1939), Ivlev (1961), Mur- pagos, these groups did not join different areas/seasons for doch (1969), Jacob (1974), Vanderploeg and Scavia (1979) the same species, although Group I is formed only by wet and Chesson (1983). On the other hand, Lawlor’s electivity season cases and Group II by open area cases (Fig. 2). A index (1980) and Braga’s degree of food preference (1999) similar pattern was obtained with the Principal Component do not take into consideration the supply of food, but merely Analysis (Fig. 3). The results of this analysis (Fig. 3, Table the quantity of items ingested by the species of fish. Accord- 2) reinforced the importance of the selectivity of the Coleop- ing to Braga (1999), the degree of food preference presented tera, Lepidoptera and Trichoptera orders for the formation of in his study is not just another index, but rather should be Group I (positive quadrant of PC1 axe), of the Ephemerop- regarded as an alternative when other methods cannot be em- 36 Uieda and Pinto & ’ ’ / 7 8 & & & ’+ &9 : 4; < & 1)! & < & ’ & & & ’ =8 3 > ? & & & & ’ " ! & 7.. ’ 70 pagos which displayed a particularly specialized diet, both ployed. Among the various indices of selectivity available in seasonally and spatially, in Diptera-Chironomidae. literature, the Ivlev index (1961) was employed for the pre- In several situations, negative indices of electivity were sent study by virtue of it being the most widely used and be- found for the insects analyzed at the order level, while posi- cause it considers both the diet of the fish and the availability tive indices for the same order were obtained when analyzing of prey in the environment, which results from the relative the families. For example, in the open area-dry season the number of items of prey, their visibility and their accessibil- two specimens of B. iheringi analyzed presented only nega- ity (Atmar and Stewart 1972). tive electivity values when the insects were analyzed at the In any analysis of feeding preference or selectivity, it is order level, but were selective for several families of insects. important to consider the sampling of available resources in These results occurred by virtue of the high standard devia- the studied environment, since the presence of a particular tion value resulting from an individual variation in the diet type of food in the digestive contents of the fish does not nec- and/or the small number of specimens analyzed. Mainly with essarily signify that it is the preferred food, bearing in mind the group of small catfish, the selectivity analysis was ad- that it may have ingested it by virtue of it being the most versely affected by the low number of specimens caught, de- widely available while the preferred food is absent, infre- spite an enormous capture effort, resulting from the low quent or difficult to catch (Zavala-Camin 1996). Pinto and abundance of this group in smaller streams. Nonetheless, it Uieda (2007) also reiterate the importance of food supply was possible to see a trend in the feeding preference for par- sampling and not just the analysis of diet when determining ticular groups of aquatic insects, but it should be stressed that feeding selectivity or preference by the species of fish, in a these data should be treated with some reservation. study conducted in the same stream in 2005 in which the in- According to Mittelbach and Persson (1998), the major- stances discovered of selectivity involved insects ingested in ity of species of fish is selective and presents a preference for both large and small quantities. specific prey. In the present study, we ascertained three situ- Among the food resources used by the ichthyofauna of ations of high-positive selectivity by aquatic insects (Table Ribeirão da Quinta, juveniles of Ephemeroptera were most 3): a) preference for very abundant item in the environment prevalent, an abundant resource in the environment and se- and consumed in high percentages (HAB/COM), a situation lected positively by the majority of the sampled species, de- encountered for all the species analyzed and predominant spite the fact that the majority presented spatial and seasonal when considering the insects at the order level; b) preference variations with this preference, with the exception of P. har- for an item not so readily available in the environment, but Feeding selectivity of ichthyofauna in a tropical stream 37 consumed in high percentage (hab/COM); c) preference for sented by a diversity of species but most in low abundance making a dietary analysis difficult; c) except for P. harpagos, an item not very abundant in the environment and consumed in low percentage (hab/com). most species showed spatial and/or temporal diet variation (item most consumed and/or selected), reinforcing their diet This variation in the feeding preference can also be seen plasticity. Those patterns were also emphasized in other stud- when the results obtained by other authors are analyzed. ies (Esteves and Aranha 1999, Sabino 1999, Uieda and Motta Three references are presented here exemplifying each of the 2007) that review the fish trophic patterns of southeastern three selectivity situations indicated above. Guma’A (1978), Brazilian streams. working on the Perca fluviatilis in a lake located in Win- By means of this study on feeding preferences by insec- dermere, also found positive selection for a species of Clado- tivorous fish species the existence of high consumption cera, a very abundant item consumed in large quantities. and/or selection for aquatic insects of different orders, Moreno and Zamorano (1980), working in Chile on a littoral mainly juveniles of Ephemeroptera, but also of Coleoptera, species of fish (Calliclinus geniguttatus), noted positive se- Trichoptera and Diptera, become clear. However, the results lectivity for a benthic item (Taliepus dentatus) that was not also highlighted that, in the absence of the preferred item or so available in the environment and consumed in high per- where availability is low, the ichthyofauna can demonstrate centage. Pinto and Uieda (2007) observed cases of selectivity a high level of feeding flexibility and an ability to adapt when for prey that was not very abundant in the environment and faced with alterations in the abiotic conditions and in the bi- consumed in low percentage for the three species of otic interactions to which these species were subjected. Once characids (Astyanax bockmani, Bryconamericus iheringi, again, the importance must be stressed of sampling the sup- Characidium zebra) and a catfish (Imparfinis borodini) ply of food and not just an analysis of diet, in order to deter- found in a stream in the southeast of Brazil. mine feeding selectivity or preferences by species of fish. In addition to the positive selectivity situations described Moreover, the feeding selectivity study opens up new pros- above, cases where the food item was fairly abundant in the pects for study such as the use of direct observation and ex- environment and consumed in high percentage, though with perimental studies, by providing the fish with two or more negative selectivity, were also detected in this study for the items of prey to be chosen in identical situations, as proposed majority of fish species, though at a far lower frequency than by Zavala-Camin (1996). that observed by Pinto and Uieda (2007). The fact that the Acknowledgments: We are grateful to C. Yoshida for her species has consumed in large quantities the most abundant comments on the manuscript and to the Brazilian Council for insect group, albeit with low selectivity, demonstrates oppor- Scientific and Technological Development (CNPq) for the tunism with the consumption of a more abundant resource, study grant awarded to the first-mentioned author during the though not necessarily the preferred one (Pinto and Uieda period of the study. 2007). Rezende and Mazzoni (2006) also demonstrated the opportunism of Bryconamericus microcephalus for References Hymenoptera, an allochthonous food item very abundant in the environment, consumed in high percentage by both !"#$ % #" #" ##! $%& %! %& young and adults and with negative selectivity. Casatti and ’& ( ’’ (’ Castro (2006) also emphasized the opportunistic behavior of )"" * + , - * some Characidae species, including two species of the Bry- As relações entre as matas ciliares, os rios e os peixes. In: R. conamericus genus. R. Rodrigues and H. F. Leitão Filho (eds.), Matas ciliares: conservação e recuperação. EDUSP and FAPESP, São Paulo. Besides this opportunism, the ichthyofauna studied here pp. 187-207. was characterized by a large trophic plasticity, evidenced by ) * O grau de preferência alimentar: um método the spatial and/or seasonal variation in the feeding prefer- qualitativo e quantitativo para o estudo do conteúdo estomacal ence, except in the case of two catfish which were caught de peixes. # )# . only in one area and one season, and P. harpagos, that has a " / 0 1#-& 2% ’ -& 3 particularly specialized diet (Table 3). The comparative !# In Guia on-line de identificação de larvas de insetos analysis (Table 4) of the results of two studies developed in aquáticos do Estado de São Paulo. Available at: the same stream (Pinto and Uieda 2007, present study) em- http://sites.ffclrp.usp.br/aguadoce/index_trico (accessed in March 2009). phasizes the opportunism, plasticity and great capacity of the $"- * 4 5 !" " !! "!! ! ichthyofauna to adjust their occurrence and diet to different 2% " 2 #-67 #! !#-! environmental characteristics that change spatial and season- &#" -! # *%!& +& . ally. Representing only the species that were common for ! /* ! Peixes de riacho both studies, except for P. harpagos, which consumed more do Parque Estadual Morro do Diabo, Bacia do Alto Rio and was selective for Diptera on all situations analyzed (ar- Paraná. Biota Neotrop. 1: 1-15. eas, seasons, studies), this comparison allowed to extract ! /* ! ( 1! - #&-" #" some conclusions: a) the species move up and downstream -%&-!! - "! !- !!2" - / changing their occurrence in a spatial and in a temporal (sea- 8 #!# 7-! )9" (!+! #,,-!& : sonal, annual) scale; b) in headstreams catfishes were repre- : 38 Uieda and Pinto -!! + ’ 1- ! "%!! &# ! Trichoptera), em córregos do parque ecológico de Goiânia, " !- & "! "#!&!.- (: : Goiás, Brasil. 50 + :!!& : ’(’( ,- ’ 0 >& -& 3!# 3 Guia "; / /< "% ( /++ 0 ,"%7- * 2 % ,"%7- on-line de identificação de larvas de insetos aquáticos do Estado de São Paulo. $"2" -&GG!!#"&7!&2 ! 3 ( "& 3 ! 3 G 7#GAH# ##!! *#- ; ! %! +! !+1! %1 #23! ="! /28 , && :. ,;! * 0"&- 3 3$! -2! "2# 2"7 7 2 " ! $, >- / * ? . 3# 2 ! && . . 72# &% &7#$% ! $2 $!% ! : , 1 4 5 67# !#! !"# ! !-! &#" ! - !&" ! !$! +*/ - #" @# &A! !" #! - !"#$%I # *%!& +& #-! 3 , !#- / *99 ,/ ,! (’ < ! "#!&!. /4 5#,! ,,5/+ / /! / 0 7"" + ! + -#; "! + && . ’ - !- !-! 7- " # !$! ,*+ " . & >3,5/ , " )9" ! #-#! !"" )9" " &" "; - ,B /$ )! "%0+!% !& $, : . ’ /9 / *99 ( >!& 2" 7! #7!! "@#! & +-#!%+# #+!#,& * B9 =/ > 79 Guía para la determi- /2 #&% -# #@ nación de los artrópodos bentônicos sudamericanos. 5$! - 3"- / + )!" 50 +& <#" 17#7B 17#7B :!!& ’ 7C ’ 1- -2 ! %7 &#- 2 + & &A! #-! J! /+# 1&0& $+,6+ !& ’ ’ !7 & 7 2 7 "K! # 3 , =! > )"% 31 =! . 5#7&" !#- / *99 ,/ ,!< ! "#!&!. ! &&% #! !! - " /4 5#,! ,,5/+ / + &&’ ’ " #&-%! ! ’ :: :: ’ #- 1 : /!7# & #" #" #7 =7# + <!! Estrutura e dis- ! )#%# ’. tribuição espacial da comunidade de larvas de Trichoptera (In- - & # ! 2 secta) em um tributário de primeira ordem do Rio Paquequer, - !& :!!& :,+ ’ . Teresópolis, RJ. # *%!& +& ( "$ * 0 &-& -& 3!# =%!"& + ’ #- #! "%!! D $ - 3 Guia on-line de identificação de larvas de insetos aquáti#! ! - &&"# 7 $, !& . ’((’ ! "! )3! /&! $"2" -&GG!! 3$"$ 4 ( "4+%& "#!&!.- !1 , $%. !1 $, #"&7!&2G 7 #G AH# ##!! *#- E" 5$!% ,!! < =$ 5 4 / * 1&-# 9 +#2 + : F7$ !7! !"# 2 !7#7 !7-! )9" !! $ # #!&!. : :: *%!& +& . "%! *= 0+- % ! % % $, 4&" = > #$ 1 "#$% #! ,0!+ & )" - !&#" # 9&"; 9 7 $, ;7#- /* 4 5 ’ Composição da comunidade 5 !+ % ( ( (. de invertebrados de um ambiente lótico tropical e sua variação ""# +) <= ! ( =2 " -!% espacial e temporal. 3 + <!! $"- 2-$ " & ! 67# !#! 3 / * ! "#!&!. %! 89#! 0#" )!"!! 7! ! % %+!#!% ! , 8# %# / + && . !1 (!+, +# ""G=7 >72767 && : " / ’ "% #& ##! "#!& ?$" ( %+!23! ! ! !; &% !.- ( :. . 23! %+& 4 >5* * B , *+) ?; Hidrobiologia de matas /#$ >#2 ciliares. In: R.R. Rodrigues and H. F. Leitão-Filho (eds.), /$! <$2 Matas ciliares: conservação e recuperação. >5, ##& >#2 ,, 8 ,7" && : : & 1"" . "#! . #!%%% & !!&!. + ! 7 Electronic appendix * / 7! ( % %+!#!% ! , 8# %# !1 (!+, +# ""G=7 >72767 Figure A1. Orders of the aquatic insects consumed and se- *"2 #- ,!! ’ 1- % &! #$ % lected by Bryconamericus iheringi sampled in the open area ! #" #" #!67#! % 7 $, 8 )# .. of Ribeirão da Quinta stream, during the dry and wet seasons, :.: :( . and in the closed area during the wet season. * += ? ’ "#$ " " ! &#! 2 ! ’.&! #,&% % &&#&% Figure A2. Orders of the aquatic insects consumed and se- .%. !& % #%!.+ :. : lected by Cetopsorhamdia iheringi sampled during wet sea- *7#- ( #- " &! A&! son in the open and closed areas of Ribeirão da Quinta & !&##% !2"% &% &&7"! "#!& stream. ’!%!.+ . .: Figure A3. Orders of the aquatic insects consumed and se- 0"$ , )!& < B Ecologia de comuni- dades de insetos bentônicos (Ephemeroptera, Plecoptera e lected by Imparfinis borodini sampled in the open area of Feeding selectivity of ichthyofauna in a tropical stream 39 Ribeirão da Quinta stream, during the dry and wet seasons, Figure A7. Orders of the aquatic insects consumed and se- and in the closed area during wet season. lected by Phalloceros harpagos sampled in the open area of Ribeirão da Quinta stream during the dry and wet seasons. Figure A4. Orders of the aquatic insects consumed and se- lected by Imparfinis mirini sampled in the open area of Table A1. Families of aquatic insects consumed by fish spe- Ribeirão da Quinta stream during the wet season. cies sampled in the open area of Ribeirão da Quinta stream during the dry and wet seasons. Figure A5. Orders of the aquatic insects consumed and se- lected by Phenacorhamdia tenebrosa sampled in the open Table A2. Families of aquatic insects consumed by fish spe- area of Ribeirão da Quinta stream during the wet season. cies sampled in the closed area of Ribeirão da Quinta stream during the dry and wet seasons. Figure A6. Orders of the aquatic insects consumed and se- lected by Trichomycterus brasiliensis sampled in the open The file may be downloaded from the web site of the publish- area of Ribeirão da Quinta stream during the dry and wet sea- er at www.akademiai.com. sons, and in the closed area during the wet season. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Community Ecology Springer Journals

Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic plasticity

Uieda, V. S.; Pinto, T. L. F.
Community Ecology , Volume 12 (1) – Jun 30, 2011
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Springer Journals
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Copyright © Akadémiai Kiadó, Budapest 2011
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1585-8553
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10.1556/ComEc.12.2011.1.5
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Abstract

!"# Feeding selectivity of ichthyofauna in a tropical stream: space-time variations in trophic plasticity 1,2 1 V. S. Uieda and T. L. F. Pinto Department of Zoology, UNESP – Univ Estadual Paulista, C.P. 510, 18618-970. Botucatu, SP, Brazil Corresponding author. Fax: 55-14-38116052, Email: [email protected] Keywords: Benthic fauna, Electivity, Fish, Food resources, Partitioning of food. Abstract: In studies on the partitioning of resources, one issue which has been largely neglected is the change in feeding habits based on the availability of food in the environment, an aspect which is dealt with here with regard to the ichthyofauna of a tropical stream. Feeding preference was analyzed for eight species of fish which consumed high percentages of aquatic insects, based on a collection of fish and invertebrates during both the dry season (June 2006) and the wet season (December 2006) and in two different stretches of the stream, one of which shaded by gallery forest (“closed area”) and the other just bordered by herbaceous vegetation (“open area”). Based on a quantitative analysis of the composition of the benthic fauna and the diet of the ichthyofauna, the electivity index was calculated in order to assess potential alterations in the feeding preferences in line with seasonal and spatial modifications to the structure of the habitat and the supply of food. The analysis of the abundance of aquatic insects in the environment showed a predominance of Ephemeroptera in all situations analyzed (areas and seasons), with this insect group being the food item preferred by the majority of fish. However, space-time variations were observed in prey selection by the ichthyofauna. The analysis of supply, consumption and preference demonstrated somewhat varied situ- ations for the majority of species, with both high and low selectivity for items consumed in low and high percentages, with the preferred item varying both spatially and seasonally. The sole exception to this was Phalloceros harpagos, choosing Diptera- Chironomidae in all the situations analyzed. Nomenclature: Reis et al. (2003) for fishes, Fernández and Domínguez (2001) for macroinvertebrates. Abbreviations: Aboc – Astyanax bockmanni, Bihe – Bryconamericus iheringi, Cihe – Cetopsorhamdia iheringi, Ibor – Im- parfinis borodini, Imir – Imparfinis mirini, Pten – Phenacorhamdia tenebrosa, Tbra – Trichomycterus brasiliensis, Phar – Phalloceros harpagos, C – Coleoptera, D – Diptera, E – Ephemeroptera, H – Heteroptera, L – Lepidoptera, M – Megaloptera, O – Odonata, P – Plecoptera, T – Trichoptera. In lotic environments, the high availability of juvenile Introduction aquatic insects makes this resource an important source of One issue which has been somewhat overlooked in stud- food for the ichthyofauna. Seasonally, aquatic insect fauna ies on the partitioning of resources is the change in feeding may undergo alterations in composition and abundance in habits, based on the availability of food, and changes in the line with alterations in the environment’s physical stability. choice of food based on quality (Esteves and Aranha 1999). In neotropical regions, the greater environmental stability in According to Zavala-Camin (1996), selectivity or choice of the dry season may ensure a larger supply of aquatic insects food cannot be solely determined by the fact of its presence (Oliveira et al. 1997, Kikuchi and Uieda, 1998, Huamantinco in the digestive contents of the fish, since it may have been and Nessimian 1999), while an increase in flow in wet season ingested, not because it was the preferred food, but because may directly remove the fauna or its food resources (Death it was the most widely available. On the other hand, a par- and Zimmermann 2005). In spatial terms, the presence of ticular food item may be selected on account of it being more gallery forests may affect the physical structure of the stream, palatable, or because it is larger or has a higher nutritional the supply of resources (Barrella et al. 2001, Lima and Zakia value and this qualitative selection of food may vary ontoge- 2001) and, consequently, the trophic organization of the netically, though it tends to be uniform amongst individuals communities (Uieda and Motta 2007). of the same species and size (Zavala-Camin 1996). Accordingly, information concerning the usage of food It is also important to remember that the selection of food is extremely important since, as well as propitiating an inter- resources in nature may be related to their availability in the esting field for the discussion of theoretical aspects, such as environment or to the active choice of specific food items by species substitution by means of the spatial, temporal and tro- predators, according to their needs (Zavala-Camin 1996). phic components in the niche (Schoener 1974), it serves Space-time factors may also have an influence on the supply other purposes such as the basic knowledge of the biology of of food as a consequence of physical changes in the environ- the species and the understanding of the trophic organization ment and may therefore alter the feeding preference. of the ecosystem (Esteves and Aranha 1999). 32 Uieda and Pinto In the present study, the fish community of a tropical moving upriver and covering the whole length of the stretch stream was studied with the aim of establishing possible al- being studied, in both areas. terations in feeding selectivity based on two gradients, sea- In the laboratory, the sampled aquatic insects were sorted sonal (dry and wet seasons) and spatial (presence or absence using stereomicroscopy and were identified using the general of gallery forest). The influence of these gradients was ana- keys of Lopretto and Tell (1995), Merritt and Cummins lyzed with regard to both the diet of ichthyofauna and the (1996) and Fernández and Domínguez (2001), but also spe- supply of food. As aquatic insects comprise the main element cific keys for certain groups. The fish taxonomic identifica- of the benthic macrofauna in this stream (Pinto and Uieda tion was checked by Dr. Francisco Langeani and the vouch- 2007), serving as a food resource for the majority of fish spe- ers are deposited in his fish collection, located in the cies present, the feeding preference was analyzed for the spe- Department of Zoology, UNESP – Univ Estadual Paulista, cies which consumed high percentages of this important food São José do Rio Preto, Brazil (DZSJRP010101 to resource. DZSJRP010117) (http://splink.cria. org.br/manager/de- tail?resource=DZSJRP-Pisces&setlang=pt). Materials and methods The determination of the fishes’ diet was conducted by analyzing the stomach contents. The Index of Relative Im- Study area portance (IRI) was calculated using the formula of Pinkas et The study was carried out at the Ribeirão da Quinta, a al. (1971): IRI = (N + V)× F, where N = the number of indi- third-order stream located in the southeast of Brazil, at an al- viduals of each insect group present in the stomach contents expressed as a percentage of the total number of individuals titude of 743 m (23 06’47"S, 48 29’46"W). This stream is part of the Paranapanema River basin and is located on cat- from all groups (numeric method, as Hyslop 1980), V = ratio tle-raising farms far away from urban areas. Two consecutive between the area occupied by a particular item and the total area occupied by all items, the area being calculated using a areas of the Ribeirão da Quinta were used for the study: one bounded by gallery forest (closed area, upstream) while the millimeter-scale plate (biovolume method, adapted from other includes treeless riverbanks (open area, downstream). Esteves and Galetti Jr. 1995), F = frequency of the item, cal- culated using the number of fish in which the food item oc- A detailed description of the type of vegetation presents there can be found in Carvalho and Uieda (2009). curred in proportion to the total occurrences of all items (fre- quency of occurrence method, as Hyslop 1980). Alternating riffles, rapids and pools can be found in both areas, with the rapids comprising the longer stretches. Al- In order to permit a comparison of diet between the dif- though the two areas have a similar substrate in terms of com- ferent species of fish, or for the same species in different ar- position and granulometry (pebbles approximately 3 cm in eas and seasons, the IRI values were transformed into relative diameter, associated with a large quantity of vegetal debris), values (%). they differ with regard to the presence of macrophytes, which Prey selectivity was calculated for each species of fish are completely absent in the closed area while in the open using the electivity index (Ivlev 1961): E = (r -P )/(r +P ), area they populate the banks and the riverbed in large quan- in which E = electivity index, r = percentage of each item in tities (predominantly Cyperaceae). The length analyzed in the stomach contents (IRI %), P = percentage of each item the closed area (24 and 17 m in the June and December col- in the environment (relative abundance). The index values lections, respectively) also differed from the open area range from -1 to +1, where a value of zero indicates null se- (lengths of 20 and 16 m per respective collection) in terms of lectivity, results <0 indicate negative selection for the item the mean values for current speed (0.24 and 0.33 m.s , in the and those values >0 denote positive selection (Zavala-Camin closed and open areas respectively), depth (0.13 and 0.22 m) 1996, Harrison et al. 2005). For the purposes of the present and width (3.2 and 1.1 m). study, a selectivity value greater than or equal to 0.5 was con- sidered to be high. The selectivity values showed in the fig- Sampling and data analysis ures and referred in the text corresponded to a mean of the index values calculated for all fish individuals of each fish The sampling of aquatic insects and fish were carried out species. These values were used to analyze the similarity in stretches of rapids in the two areas (closed and open) and (group average clustering with Euclidean distance) between in two seasons of the year (June 2006 – dry season, and De- the diet of species sampled in the two areas and seasons, and cember 2006 – wet season). The benthic macroinvertebrates also Principal Components Analysis to determine the contri- were sampled using a Surber net (900 cm ; mesh 0.250 mm) bution of each insect order to this similarity (Primer v.6; in a total of 10 replications per area and per season. For the Clarke and Gorley 2006). sampling of ichthyofauna a gill net was used (2 mm plastic mesh) and the catching effort was standardized (4 collectors, Results 2 hours per area). The net was settled transversely to the river, bridging the two banks, with the substrate in front of the net being stirred up by feet and hands in order to dislodge A total of ten species of fish were collected at Ribeirão the fish, which were subsequently transported by the current da Quinta, but only two Loricariidae species - Hisonotus de- into the net. The sampling was conducted at intervals of 2 m, pressicauda (Miranda Ribeiro, 1918) and Hypostomus ni- Feeding selectivity of ichthyofauna in a tropical stream 33 ! " #$ % & & ! ’ ( & Trichoptera families (Leptoceridae and Polycentropodidae) gromaculatus (Schubart,1964) – consumed mainly periphy- stood out as having high selectivity, though with low con- ton (more than 75% of the food ingested). For the other eight sumption. species (Table 1) aquatic insects were the main food item in- gested. Five of these species corresponded to small catfish, With regard to B. iheringi, it was possible to ascertain of which four belong to the Heptapteridae family - Cetop- spatial and seasonal differences in diet (Fig. A1 in Appen- sorhamdia iheringi Vari & Castro, 2007; Imparfinis borodini dix). In the open area-dry season, this species consumed a Mees & Cala, 1989; Imparfinis mirini Haseman, 1911; Phen- high percentage and presented positive selectivity for Ephe- acorhamdia tenebrosa (Schubart, 1964) – and one to the meroptera-Leptophlebiidae (Fig. A1a, Table A1). In spite of Trichomycteridae family - Trichomycterus brasiliensis Lut- the negative selectivity values for the other orders, high posi- ken, 1874. The species Phalloceros harpagos Lucinda, 2008 tive selectivity was found for a family of Coleoptera – Poeciliidae was the only species sampled in the closed area (Psephenidae) consumed in low percentage. On the other during the dry season. The other two species belong to the hand, also in this area, but in the wet season (Fig. A1b), this Characidae family – Astyanax bockmani Vari & Castro, 2007 species presented negative electivity values for all orders of insects consumed, despite the high-positive electivity values and Bryconamericus iheringi (Boulenger, 1887). for Coleoptera-Psephenidae, consumed in high percentage, The analysis of abundance of aquatic insects in the envi- and for a further five families, within the orders Lepidoptera, ronment showed a predominance of Ephemeroptera in all the Odonata and Trichoptera, with low consumption (Table A1). situations analyzed (Table 1), with the few differences found In the closed area, this species only occurred in the wet sea- between areas and seasons relating to the second and/or third son, when it consumed a larger percentage and presented most abundant groups, although in this case they always var- positive selectivity for Lepidoptera and Trichoptera (Fig. ied between Diptera, Trichoptera and Coleoptera, in roughly A1c). However, when analyzed at the family level, the highest equal proportions. Despite this similarity in the existing re- selectivity values stood out for Coleoptera-Curculionidae, sources, it was possible to ascertain spatial and time differ- Plecoptera-Perlidae and Lepidoptera-Pyralidae (Table A2). ences in terms of consumption and feeding selectivity by the ichthyofauna (Fig. 1, Figs. A1 to A7 in Appendix). Occurring only in the wet season in the two areas, C. iheringi presented an apparent spatial variation in diet, in the In the open area-dry season, the species A. bockmanni open area consuming in high percentage and with high-posi- presented a larger consumption and positive selectivity for tive selectivity for Plecoptera-Perlidae and Diptera-Simulii- Diptera and Trichoptera (Fig. 1a), with a high electivity in- dae (Fig. A2a, Table A1 in Appendix), while in the closed area dex value for Diptera-Chironomidae, consumed in high per- it consumed a high percentage and presented a high value of se- centage, and for two families of Trichoptera (Hydroptilidae lectivity for Diptera-Chironomidae (Fig. A2b, Table A2). and Leptoceridae), consumed in low percentages (Table A1 in Appendix). As for the remaining insect groups, A. bock- As for I. borodini, it was also possible to ascertain spatial manni presented negative selectivity values. However, when and seasonal differences in the diet (Fig. A3 in Appendix). analyzing the diet of this species in the wet season, a greater Despite the individuals of this species of catfish captured in consumption and a high-positive selectivity was observed for the open area having consumed a high percentage of Ephe- Ephemeroptera (Fig. 1b), mainly Baetidae (Table A1). Also meroptera in both seasons, it only presented high and posi- in the wet season, despite A. bockmanni having presented tive values of selectivity for this order in the wet season (Figs. negative selectivity for the other orders of insects, on analyz- A3b). In addition, in the dry season, when analyzed at the ing the families, one Diptera (Ceratopogonidae) and two family level (Table A1), it was highly selective for Ephe- 34 Uieda and Pinto ) & & * & ’ ( & ’ - ./ & ’ . ( 0’ / & & ) 1 & * + + ’ tera-Leptophlebiidae, Trichoptera-Hydroptilidae and meroptera-Baetidae and for two families of Trichoptera Trichoptera-Philopotamidae (Fig. A5, Table A1 in Appen- (Glossosomatidae and Hydropsychidae), the second most dix). consumed in percentage terms similar to that of the Baetidae, whereas in the wet season it presented high-positive selectiv- As for T. brasiliensis, spatial and seasonal differences ity for Ephemeroptera-Leptophlebiidae, Lepidoptera-Pyrali- were also noted in the diet (Fig. A6). In the open area, in both seasons, this species consumed a high percentage and pre- dae and Diptera-Simuliidae, with only the first mentioned having a high percentage of consumption (Table A1). In the sented high, positive selectivity for Ephemeroptera, though closed area-wet season, I. borodini presented a high con- with higher IRI and E values for Baetidae in the dry season and for Leptophlebiidae in the wet season (Table A1). The sumption of Coleoptera and Trichoptera, but positive selec- tivity only in the case of the former (Fig. A3c). However, specimens of T. brasiliensis collected in the closed area-wet when analyzing the families, high values of positive selectiv- season consumed the most in percentage terms and presented high-positive selectivity for Diptera and Trichoptera (Fig. ity were observed, both for three Coleoptera families (Dryopidae, Elmidae and Psephenidae) and for Trichoptera- A6c). However, at the family level, high-positive selectivity Hydroptilidae, consumed in a similar percentage to that of was detected only for Diptera-Chironomidae (Table A2). In the latter two families of Coleoptera (Table A2). this case, the high consumption of Trichoptera relates to ju- veniles that could not be identified at the family level. As for the other two species of Heptapteridae, in spite of the fact that only one specimen of each was analyzed, it was With regard to P. harpagos, as well as being the species possible to detect a tendency towards a more specialized diet with the largest number of specimens studied, it was the only for I. mirini, with high consumption and high-positive selec- one collected in all the situations analyzed. This species pre- tivity for Ephemeroptera-Baetidae (Fig. A4, Table A1 in Ap- sented quite a uniform diet, both spatially and temporally, pendix).. On the other hand, P. tenebrosa consumed in high consuming in a high percentage and with high-positive selec- percentage and presented positive selectivity for Ephemerop- tivity for Diptera-Chironomidae (Fig. A7, Tables A1 and A2 Feeding selectivity of ichthyofauna in a tropical stream 35 & 3 1 tera order for the formation of Group II (negative quadrant of ’ & & PC2 axis), and of Diptera order for the formation of Group & & III (positive quadrant of PC2 axis). Discussion Fish communities in neotropical streams present a great diversity of feeding habits and tactics, thus reflecting the in- credible variety of available aquatic organisms as potential prey (Keenleyside 1979). For the families of species of fish collected from Ribeirão da Quinta, different feeding strate- gies have been recognized (Casatti et al. 2001, Casatti and Castro 2006): the family Characidae brings together species of nektonic fish which collect items of food dragged along by the current; the species of Poeciliidae family prefers to sur- vive in the backwaters and catches its prey on the surface; the small catfish of Heptapteridae and Trichomycteridae fami- lies are predominantly benthic species that hunt aquatic in- sects while inspecting the substrate. The capture technique is associated with the type of food, with no special technique being required for capturing vege- tal materials, which require suitable morphological struc- tures (Keenleyside 1979). On the other hand, for capturing moving organisms, behavioral and structural adaptations re- lating to predator-prey interaction are required (Keenleyside 1979). The large supply of these moving organisms, represented in the stream by juvenile aquatic insects, makes this resource an important item in the fish’s diet. According to Wallace and & 3 1 4 Anderson (1996), the great success of aquatic insects in the 315 31+ ’ & ’ / continental environment may be demonstrated by their diver- & & ) 1 sity, abundance, wide distribution and ability to inhabit di- & + verse types of environments. In the present study, some 2 6 & & groups were conspicuous for their high abundance, such as & " the orders Ephemeroptera, Diptera, Trichoptera and Coleop- ’ & 4 & & 6 5 tera, found in a broad diversity of situations, such as pools and riffles, rock and leaf substrates, and in great diversity of lotic environments, as second and third-order streams (Costa and Ide 2006, Calor 2007, Silva 2007, Pinho 2008). in Appendix). Only in the open area-wet season, P. harpagos also presented high selectivity for Diptera-Ceratopogonidae, These high levels of variety and abundance of food rep- despite the low consumption (Table A1). resented by aquatic insects, along with the use of different The analysis of similarity based on the electivity index feeding tactics by the ichthyofauna studied, help with the calculated for the insect orders consumed by the eight fish feeding selection or preference, which can be defined as a species (Fig. 2) reinforced this spatial and seasonal diet simi- behavior that determines the choice of the food best suited to larity for P. harpagos. The dendrogram also showed the ex- the needs of the fish (Zavala-Camin 1996). In order to calcu- istence of three major groups of cases (species/area/season) late this preference, the literature contains different electivity with positive electivity index occurring for: Coleoptera, indices that correlate the food item available in the environ- Lepidoptera and Trichoptera (Group I), for Ephemeroptera ment with the item ingested by the fish, with particular men- (Group II), and for Diptera (Group III). Except for P. har- tion for the indices of Shorigin (1939), Ivlev (1961), Mur- pagos, these groups did not join different areas/seasons for doch (1969), Jacob (1974), Vanderploeg and Scavia (1979) the same species, although Group I is formed only by wet and Chesson (1983). On the other hand, Lawlor’s electivity season cases and Group II by open area cases (Fig. 2). A index (1980) and Braga’s degree of food preference (1999) similar pattern was obtained with the Principal Component do not take into consideration the supply of food, but merely Analysis (Fig. 3). The results of this analysis (Fig. 3, Table the quantity of items ingested by the species of fish. Accord- 2) reinforced the importance of the selectivity of the Coleop- ing to Braga (1999), the degree of food preference presented tera, Lepidoptera and Trichoptera orders for the formation of in his study is not just another index, but rather should be Group I (positive quadrant of PC1 axe), of the Ephemerop- regarded as an alternative when other methods cannot be em- 36 Uieda and Pinto & ’ ’ / 7 8 & & & ’+ &9 : 4; < & 1)! & < & ’ & & & ’ =8 3 > ? & & & & ’ " ! & 7.. ’ 70 pagos which displayed a particularly specialized diet, both ployed. Among the various indices of selectivity available in seasonally and spatially, in Diptera-Chironomidae. literature, the Ivlev index (1961) was employed for the pre- In several situations, negative indices of electivity were sent study by virtue of it being the most widely used and be- found for the insects analyzed at the order level, while posi- cause it considers both the diet of the fish and the availability tive indices for the same order were obtained when analyzing of prey in the environment, which results from the relative the families. For example, in the open area-dry season the number of items of prey, their visibility and their accessibil- two specimens of B. iheringi analyzed presented only nega- ity (Atmar and Stewart 1972). tive electivity values when the insects were analyzed at the In any analysis of feeding preference or selectivity, it is order level, but were selective for several families of insects. important to consider the sampling of available resources in These results occurred by virtue of the high standard devia- the studied environment, since the presence of a particular tion value resulting from an individual variation in the diet type of food in the digestive contents of the fish does not nec- and/or the small number of specimens analyzed. Mainly with essarily signify that it is the preferred food, bearing in mind the group of small catfish, the selectivity analysis was ad- that it may have ingested it by virtue of it being the most versely affected by the low number of specimens caught, de- widely available while the preferred food is absent, infre- spite an enormous capture effort, resulting from the low quent or difficult to catch (Zavala-Camin 1996). Pinto and abundance of this group in smaller streams. Nonetheless, it Uieda (2007) also reiterate the importance of food supply was possible to see a trend in the feeding preference for par- sampling and not just the analysis of diet when determining ticular groups of aquatic insects, but it should be stressed that feeding selectivity or preference by the species of fish, in a these data should be treated with some reservation. study conducted in the same stream in 2005 in which the in- According to Mittelbach and Persson (1998), the major- stances discovered of selectivity involved insects ingested in ity of species of fish is selective and presents a preference for both large and small quantities. specific prey. In the present study, we ascertained three situ- Among the food resources used by the ichthyofauna of ations of high-positive selectivity by aquatic insects (Table Ribeirão da Quinta, juveniles of Ephemeroptera were most 3): a) preference for very abundant item in the environment prevalent, an abundant resource in the environment and se- and consumed in high percentages (HAB/COM), a situation lected positively by the majority of the sampled species, de- encountered for all the species analyzed and predominant spite the fact that the majority presented spatial and seasonal when considering the insects at the order level; b) preference variations with this preference, with the exception of P. har- for an item not so readily available in the environment, but Feeding selectivity of ichthyofauna in a tropical stream 37 consumed in high percentage (hab/COM); c) preference for sented by a diversity of species but most in low abundance making a dietary analysis difficult; c) except for P. harpagos, an item not very abundant in the environment and consumed in low percentage (hab/com). most species showed spatial and/or temporal diet variation (item most consumed and/or selected), reinforcing their diet This variation in the feeding preference can also be seen plasticity. Those patterns were also emphasized in other stud- when the results obtained by other authors are analyzed. ies (Esteves and Aranha 1999, Sabino 1999, Uieda and Motta Three references are presented here exemplifying each of the 2007) that review the fish trophic patterns of southeastern three selectivity situations indicated above. Guma’A (1978), Brazilian streams. working on the Perca fluviatilis in a lake located in Win- By means of this study on feeding preferences by insec- dermere, also found positive selection for a species of Clado- tivorous fish species the existence of high consumption cera, a very abundant item consumed in large quantities. and/or selection for aquatic insects of different orders, Moreno and Zamorano (1980), working in Chile on a littoral mainly juveniles of Ephemeroptera, but also of Coleoptera, species of fish (Calliclinus geniguttatus), noted positive se- Trichoptera and Diptera, become clear. However, the results lectivity for a benthic item (Taliepus dentatus) that was not also highlighted that, in the absence of the preferred item or so available in the environment and consumed in high per- where availability is low, the ichthyofauna can demonstrate centage. Pinto and Uieda (2007) observed cases of selectivity a high level of feeding flexibility and an ability to adapt when for prey that was not very abundant in the environment and faced with alterations in the abiotic conditions and in the bi- consumed in low percentage for the three species of otic interactions to which these species were subjected. Once characids (Astyanax bockmani, Bryconamericus iheringi, again, the importance must be stressed of sampling the sup- Characidium zebra) and a catfish (Imparfinis borodini) ply of food and not just an analysis of diet, in order to deter- found in a stream in the southeast of Brazil. mine feeding selectivity or preferences by species of fish. In addition to the positive selectivity situations described Moreover, the feeding selectivity study opens up new pros- above, cases where the food item was fairly abundant in the pects for study such as the use of direct observation and ex- environment and consumed in high percentage, though with perimental studies, by providing the fish with two or more negative selectivity, were also detected in this study for the items of prey to be chosen in identical situations, as proposed majority of fish species, though at a far lower frequency than by Zavala-Camin (1996). that observed by Pinto and Uieda (2007). The fact that the Acknowledgments: We are grateful to C. Yoshida for her species has consumed in large quantities the most abundant comments on the manuscript and to the Brazilian Council for insect group, albeit with low selectivity, demonstrates oppor- Scientific and Technological Development (CNPq) for the tunism with the consumption of a more abundant resource, study grant awarded to the first-mentioned author during the though not necessarily the preferred one (Pinto and Uieda period of the study. 2007). Rezende and Mazzoni (2006) also demonstrated the opportunism of Bryconamericus microcephalus for References Hymenoptera, an allochthonous food item very abundant in the environment, consumed in high percentage by both !"#$ % #" #" ##! $%& %! %& young and adults and with negative selectivity. Casatti and ’& ( ’’ (’ Castro (2006) also emphasized the opportunistic behavior of )"" * + , - * some Characidae species, including two species of the Bry- As relações entre as matas ciliares, os rios e os peixes. In: R. conamericus genus. R. Rodrigues and H. F. Leitão Filho (eds.), Matas ciliares: conservação e recuperação. EDUSP and FAPESP, São Paulo. Besides this opportunism, the ichthyofauna studied here pp. 187-207. was characterized by a large trophic plasticity, evidenced by ) * O grau de preferência alimentar: um método the spatial and/or seasonal variation in the feeding prefer- qualitativo e quantitativo para o estudo do conteúdo estomacal ence, except in the case of two catfish which were caught de peixes. # )# . only in one area and one season, and P. harpagos, that has a " / 0 1#-& 2% ’ -& 3 particularly specialized diet (Table 3). The comparative !# In Guia on-line de identificação de larvas de insetos analysis (Table 4) of the results of two studies developed in aquáticos do Estado de São Paulo. Available at: the same stream (Pinto and Uieda 2007, present study) em- http://sites.ffclrp.usp.br/aguadoce/index_trico (accessed in March 2009). phasizes the opportunism, plasticity and great capacity of the $"- * 4 5 !" " !! "!! ! ichthyofauna to adjust their occurrence and diet to different 2% " 2 #-67 #! !#-! environmental characteristics that change spatial and season- &#" -! # *%!& +& . ally. Representing only the species that were common for ! /* ! Peixes de riacho both studies, except for P. harpagos, which consumed more do Parque Estadual Morro do Diabo, Bacia do Alto Rio and was selective for Diptera on all situations analyzed (ar- Paraná. Biota Neotrop. 1: 1-15. eas, seasons, studies), this comparison allowed to extract ! /* ! ( 1! - #&-" #" some conclusions: a) the species move up and downstream -%&-!! - "! !- !!2" - / changing their occurrence in a spatial and in a temporal (sea- 8 #!# 7-! )9" (!+! #,,-!& : sonal, annual) scale; b) in headstreams catfishes were repre- : 38 Uieda and Pinto -!! + ’ 1- ! "%!! &# ! Trichoptera), em córregos do parque ecológico de Goiânia, " !- & "! "#!&!.- (: : Goiás, Brasil. 50 + :!!& : ’(’( ,- ’ 0 >& -& 3!# 3 Guia "; / /< "% ( /++ 0 ,"%7- * 2 % ,"%7- on-line de identificação de larvas de insetos aquáticos do Estado de São Paulo. $"2" -&GG!!#"&7!&2 ! 3 ( "& 3 ! 3 G 7#GAH# ##!! *#- ; ! %! +! !+1! %1 #23! ="! /28 , && :. ,;! * 0"&- 3 3$! -2! "2# 2"7 7 2 " ! $, >- / * ? . 3# 2 ! && . . 72# &% &7#$% ! $2 $!% ! : , 1 4 5 67# !#! !"# ! !-! &#" ! - !&" ! !$! +*/ - #" @# &A! !" #! - !"#$%I # *%!& +& #-! 3 , !#- / *99 ,/ ,! (’ < ! "#!&!. /4 5#,! ,,5/+ / /! / 0 7"" + ! + -#; "! + && . ’ - !- !-! 7- " # !$! ,*+ " . & >3,5/ , " )9" ! #-#! !"" )9" " &" "; - ,B /$ )! "%0+!% !& $, : . ’ /9 / *99 ( >!& 2" 7! #7!! "@#! & +-#!%+# #+!#,& * B9 =/ > 79 Guía para la determi- /2 #&% -# #@ nación de los artrópodos bentônicos sudamericanos. 5$! - 3"- / + )!" 50 +& <#" 17#7B 17#7B :!!& ’ 7C ’ 1- -2 ! %7 &#- 2 + & &A! #-! J! /+# 1&0& $+,6+ !& ’ ’ !7 & 7 2 7 "K! # 3 , =! > )"% 31 =! . 5#7&" !#- / *99 ,/ ,!< ! "#!&!. ! &&% #! !! - " /4 5#,! ,,5/+ / + &&’ ’ " #&-%! ! ’ :: :: ’ #- 1 : /!7# & #" #" #7 =7# + <!! Estrutura e dis- ! )#%# ’. tribuição espacial da comunidade de larvas de Trichoptera (In- - & # ! 2 secta) em um tributário de primeira ordem do Rio Paquequer, - !& :!!& :,+ ’ . Teresópolis, RJ. # *%!& +& ( "$ * 0 &-& -& 3!# =%!"& + ’ #- #! "%!! D $ - 3 Guia on-line de identificação de larvas de insetos aquáti#! ! - &&"# 7 $, !& . ’((’ ! "! )3! /&! $"2" -&GG!! 3$"$ 4 ( "4+%& "#!&!.- !1 , $%. !1 $, #"&7!&2G 7 #G AH# ##!! *#- E" 5$!% ,!! < =$ 5 4 / * 1&-# 9 +#2 + : F7$ !7! !"# 2 !7#7 !7-! )9" !! $ # #!&!. : :: *%!& +& . "%! *= 0+- % ! % % $, 4&" = > #$ 1 "#$% #! ,0!+ & )" - !&#" # 9&"; 9 7 $, ;7#- /* 4 5 ’ Composição da comunidade 5 !+ % ( ( (. de invertebrados de um ambiente lótico tropical e sua variação ""# +) <= ! ( =2 " -!% espacial e temporal. 3 + <!! $"- 2-$ " & ! 67# !#! 3 / * ! "#!&!. %! 89#! 0#" )!"!! 7! ! % %+!#!% ! , 8# %# / + && . !1 (!+, +# ""G=7 >72767 && : " / ’ "% #& ##! "#!& ?$" ( %+!23! ! ! !; &% !.- ( :. . 23! %+& 4 >5* * B , *+) ?; Hidrobiologia de matas /#$ >#2 ciliares. In: R.R. Rodrigues and H. F. Leitão-Filho (eds.), /$! <$2 Matas ciliares: conservação e recuperação. >5, ##& >#2 ,, 8 ,7" && : : & 1"" . "#! . #!%%% & !!&!. + ! 7 Electronic appendix * / 7! ( % %+!#!% ! , 8# %# !1 (!+, +# ""G=7 >72767 Figure A1. Orders of the aquatic insects consumed and se- *"2 #- ,!! ’ 1- % &! #$ % lected by Bryconamericus iheringi sampled in the open area ! #" #" #!67#! % 7 $, 8 )# .. of Ribeirão da Quinta stream, during the dry and wet seasons, :.: :( . and in the closed area during the wet season. * += ? ’ "#$ " " ! &#! 2 ! ’.&! #,&% % &&#&% Figure A2. Orders of the aquatic insects consumed and se- .%. !& % #%!.+ :. : lected by Cetopsorhamdia iheringi sampled during wet sea- *7#- ( #- " &! A&! son in the open and closed areas of Ribeirão da Quinta & !&##% !2"% &% &&7"! "#!& stream. ’!%!.+ . .: Figure A3. Orders of the aquatic insects consumed and se- 0"$ , )!& < B Ecologia de comuni- dades de insetos bentônicos (Ephemeroptera, Plecoptera e lected by Imparfinis borodini sampled in the open area of Feeding selectivity of ichthyofauna in a tropical stream 39 Ribeirão da Quinta stream, during the dry and wet seasons, Figure A7. Orders of the aquatic insects consumed and se- and in the closed area during wet season. lected by Phalloceros harpagos sampled in the open area of Ribeirão da Quinta stream during the dry and wet seasons. Figure A4. Orders of the aquatic insects consumed and se- lected by Imparfinis mirini sampled in the open area of Table A1. Families of aquatic insects consumed by fish spe- Ribeirão da Quinta stream during the wet season. cies sampled in the open area of Ribeirão da Quinta stream during the dry and wet seasons. Figure A5. Orders of the aquatic insects consumed and se- lected by Phenacorhamdia tenebrosa sampled in the open Table A2. Families of aquatic insects consumed by fish spe- area of Ribeirão da Quinta stream during the wet season. cies sampled in the closed area of Ribeirão da Quinta stream during the dry and wet seasons. Figure A6. Orders of the aquatic insects consumed and se- lected by Trichomycterus brasiliensis sampled in the open The file may be downloaded from the web site of the publish- area of Ribeirão da Quinta stream during the dry and wet sea- er at www.akademiai.com. sons, and in the closed area during the wet season.

Journal

Community Ecology – Springer Journals

Published: Jun 30, 2011

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