ICES Journal of Marine Science: Journal du Conseil

Powers, Joseph E.; Brooks, Elizabeth N.

doi: 10.1093/icesjms/fsn133pmid: N/A

Powers, J. E., and Brooks, E. N. 2008. Penalties and rewards for over- and underages of catch allocations. ICES Journal of Marine Science, 65: 15411551.Many fisheries are managed using a total allowable catch (TAC) that is subsequently sub-allocated to different fisheries sectors. These allocations are then monitored separately to ensure the adherence of each fishery to its particular allocation quota and to the overall TAC. In some management arenas, there are systems of payback where over- and underages are punished or rewarded using particular decision rules. Differences between fishing gear, the sizes and ages of fish being targeted by those gears, and the spatio-temporal distribution of the fishers using those gears can lead to different precision, accuracy, and cost of monitoring the allocation, affecting the probability that an overall management objective is reached. Weaknesses in monitoring may be exploited by user groups in their competition for larger catches and, subsequently, bigger allocations, so differential monitoring precision and accuracy can lead to both short- and long-term reallocations, i.e. a new set of winners and losers. Simulations in a management strategy evaluation framework were used to demonstrate the implications of alternative decision rules regarding payback on conservation and sustainability objectives and rebuilding time frames. The efficacy of the rules under alternative monitoring systems was also examined. Decision rules allowing payback prolong rebuilding (compared with perfect implementation or more precautionary TACs), especially if monitoring is biased (catches misreported) or imprecise. When precision of reported catches was increased and/or bias decreased, better yields and stock abundance resulted. When overages were penalized and underages not rewarded, recovery was achieved earlier. Conversely, policies in which transgressions were ignored and underages rewarded did not perform well. Underreporting by one nation may result in stocks that are well below the stock size conservation standards, yet produce substantial gains in yield for that nation, unless other nations retaliate by underreporting.

Lee, Ji Hoon; Karlsen, Ludvig; Lee, Chun Woo

doi: 10.1093/icesjms/fsn126pmid: N/A

Lee, J. H., Karlsen, L., and Lee, C. W. 2008. A method for improving the dynamic simulation efficiency of underwater flexible structures by implementing non-active points in modelling. ICES Journal of Marine Science, 65: 15521558.The implementation of non-active points into a conventional mass spring network for improving the simulation efficiency of fishing gear systems is presented. A conventional mass spring network generally consists of just active mass points involved in physical calculations, and non-active points located between neighbouring active mass points are not involved in the calculations. For each time-step, new positions for non-active points are calculated based on the active mass point positions already calculated for that time-step. By replacing some active mass points with non-active ones, computing time can be reduced while maintaining accuracy in the ground-interference simulation. As this method is more efficient in demonstrating the behaviour of fishing gear such as bottom longlines and bottom gillnets, an adaptive non-active point model represents the shape of a system more accurately than one consisting of just active mass points.

Pitois, Sophie G.; Fox, Clive J.

doi: 10.1093/icesjms/fsn150pmid: N/A

Pitois, S. G., and Fox, C. J. 2008. Empirically modelling the potential effects of changes in temperature and prey availability on the growth of cod larvae in UK shelf seas. ICES Journal of Marine Science, 65: 15591572.It has been hypothesized that changes in zooplankton community structure over the past four decades led to reduced growth and survival of prerecruit Atlantic cod (Gadus morhua) and that this was a key factor underlying poor year classes, contributing to stock collapse, and inhibiting the recovery of stocks around the UK. To evaluate whether observed changes in plankton abundance, species composition and temperature could have led to periods of poorer growth of cod larvae, we explored the effect of prey availability and temperature on early larval growth using an empirical trophodynamic model. Prey availability was parameterized using species abundance data from the Continuous Plankton Recorder. Our model suggests that the observed changes in plankton community structure in the North Sea may have had less impact on cod larval growth, at least for the first 40 days following hatching, than previously suggested. At least in the short term, environmental and prey conditions should be able to sustain growth of cod larvae and environmental changes acting on this early life stage should not limit stock recovery.

Goodsir, Freya; Armstrong, Michael J.; Witthames, Peter R.; Maxwell, David L.; Fox, Clive J.

doi: 10.1093/icesjms/fsn180pmid: N/A

Goodsir, F., Armstrong, M. J., Witthames, P. R., Maxwell, D. L., and Fox, C. J. 2008. The use of species-specific TaqMan probes for identifying early stage gadoid eggs following formaldehyde fixation. ICES Journal of Marine Science, 65: 15731577.Surveys of fish eggs are increasingly being used to monitor the spawning areas and stock status of commercially important species such as Atlantic cod (Gadus morhua), but early stage cod eggs are visually indistinguishable from those of several other common co-occurring species, including haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus). In recent surveys in the Irish and North Seas, a molecular identification technique (TaqMan multiplex real-time polymerase chain-reaction) assay has been used to overcome this problem. The method needs high-quality DNA, so the current protocol requires that individual cod-like eggs are presorted from plankton hauls on board ship and immediately preserved in ethanol. This increases seagoing staff costs, can be a difficult process at sea, and means that plankton sampling cannot be undertaken from non-specialized vessels such as fishing boats. Successful application of TaqMan probes to DNA from eggs preserved in formalin would overcome these problems, but previous attempts have resulted in poor success. In this study, batches of hatchery-sourced cod, haddock, and whiting eggs were fixed in 4 buffered formalin for up to 3 weeks, then transferred to a formaldehyde-free solution for 1, 2, or 3 months. After these periods they were assessed visually for fixation quality and analysed using species-specific TaqMan probes. Eggs, which had been fixed for up to 3 weeks in formalin, were identified successfully, although the positive rate (8496) was slightly lower than samples preserved throughout in ethanol (9299). There was no increase in the percentage of eggs misidentified comparing formalin-fixed and ethanol-preserved material. These results suggest that TaqMan probes can be applied successfully to fish eggs fixed in 4 buffered formalin for up to 3 weeks.

Stentiford, Grant D.

doi: 10.1093/icesjms/fsn134pmid: N/A

Stentiford, G. D. 2008. Diseases of the European edible crab (Cancer pagurus): a review. ICES Journal of Marine Science, 65: 15781592.The edible crab (Cancer pagurus) supports an important fishery in European waters. The fishery is increasing in size and in relative importance as stocks of marine finfish decline. Despite its importance, though, studies on the pathogens and parasites of this crab species are relatively lacking compared with studies of commercially exploited finfish and molluscan hosts. Recent basic surveys of C. pagurus stocks from the English Channel carried out by the Cefas laboratory at Weymouth have identified a new viral infection (C. pagurus bacilliform virus, CpBV) in juvenile crabs, and several new species of protistan parasite (Hematodinium sp., Paramarteilia canceri, and Enterospora canceri) in the adult population. The histopathology and prevalence of each of these pathogens suggests that each can induce host mortality and, further, that specific pathogens are differentially prevalent in juvenile and adult cohorts from similar geographic locations and at different times of the year. In this review, these newly discovered pathogens are placed in context with previously described bacterial, fungal, protistan, and metazoan pathogens of C. pagurus, and the potential for these pathogens to impact on the health of individuals and populations within the English Channel fishery is discussed.

Niamaimandi, Nassir; Aziz, Arshad; Siti Khalijah, Daud; Che Roos, Saed; Kiabi, Bahram

doi: 10.1093/icesjms/fsn172pmid: N/A

Abstract Niamaimandi, N., Aziz, A., Siti Khalijah, D., Che Roos, S. and Kiabi, B. 2008. Reproductive biology of the green tiger prawn (Penaeus semisulcatus) in coastal waters of Bushehr, Persian Gulf. – ICES Journal of Marine Science, 65: 1593–1599. The reproductive cycle of the green tiger prawn (Penaeus semisulcatus) was investigated in the coastal waters of Bushehr, Iran, Persian Gulf, from January 2003 to March 2004, with the aim of determining spawning seasons, durations, and locations in those waters. Bushehr waters are one of the main fishing grounds for P. semisulcatus in the Persian Gulf. Spawning peaks between December and March, but there is also some spawning in October. The minimum size at maturity was 24 mm carapace length (CL), and 50% were mature at 40 mm CL. The proportion of females that mated increased sharply above this size (40 mm), with 90% of females sexually mature at 54 mm CL. Spawning took place in a limited part of the study area, mostly offshore. Overexploiting the spawning stock could result in reduced reproductive output, limiting fishery production. Introduction Commercial exploitation of prawns on the Iranian side of the Persian Gulf began in 1959 (Boerema, 1969). Then, fishing was restricted to the Bushehr area and a single species, the green tiger prawn (Penaeus semisulcatus), but since then, the number of species fished has increased. In terms of commercial catch, though, P. semisulcatus remains the most important species in the Persian Gulf, accounting for ∼95% of the shrimp and prawn landings into Bahrain (Abdulqader, 1999), 60% into Kuwait (Ye et al., 1999), and 95% into Saudi Arabia (Sakurai, 1998). In Iran, P. semisulcatus accounts for >80% of the landed catch (Khorshidian, 2002). Knowledge of spawning seasons and areas are important to management and hence to studies of the reproductive dynamics of commercially important species. The spawning seasons of penaeid prawns have been determined in other studies either by evaluating changes in the percentage of mature females in the catch or by changes in gonadal indices (Crocos, 1985). Management advice on prawn stocks is frequently hampered by inadequate knowledge of the factors influencing reproduction. There have been many studies on the reproductive dynamics of penaeid prawns (Penn, 1980; Crocos and Kerr, 1983; Buckworth, 1985; Garcia, 1985). Somers and Kirkwood (1991) investigated the reproductive biology and life cycle of P. semisulcatus in the Groote Eylandt, Australia, and concluded that like many other penaeid prawn species, P. semisulcatus spawns offshore. King (1995) stated that for marine species, up to 96% of fish and invertebrate eggs are fertilized and hatch into larvae in the open sea. Shrimp and prawn fisheries in the Bushehr area are currently managed by a minimum stock strategy in an attempt to prevent overfishing. Under this strategy, the catch rate (catch per unit effort, cpue) is used as an index of stock abundance. Enforcement, to protect nursery and spawning grounds, is limited by the paucity of biological reference data. Although many studies have been conducted on Iranian shrimp and prawn resources, knowledge of the biology and behaviour of individual species is still sparse. The first stock assessment of P. semisulcatus in Bushehr waters was undertaken in 1982 (Azimi, 1985). In 1991 and 1992, two projects on the biology and the population dynamics were carried out by the Persian Gulf Fisheries Research Center in Bushehr (Ghasemi and Niamaimandi, 1994). The most recent investigation of P. semisulcatus in the Bushehr area was in 1996, and it included more studies of the population dynamics as well as attempts to improve the stock assessments (Niamaimandi, 1997). The current study is limited to Bushehr coastal waters of the Persian Gulf. Its purpose was to determine the spawning seasons and duration, the areas of P. semisulcatus presence, and also the spawning activity in Bushehr waters, to understand better the maturation processes required for improved stock management. Material and methods The reproductive biology of P. semisulcatus was investigated during a series of bottom-trawl surveys conducted by RV “Lavar II” from January 2003 to March 2004. The vessel towed a net with a mesh size of 40 mm in the body and the codend. A speed of 3 knots was maintained for 1 h during sampling, and time, depth, and position at the start and end of each haul were noted. The study area extended from 49°45′E to 51°57′E and from 27°29′N to 30°03′N, covering the total known commercial fishing grounds off Iran for P. semisulcatus (Figure 1). In all, 50 fixed stations were sampled monthly. From each haul, 5 kg (∼500 specimens) of P. semisulcatus were removed and sorted by sex. Where the total catch was <5 kg, the entire catch was included. Carapace length (CL) was measured from the post-orbital notch of the carapace to the mid-posterior dorsal margin (±0.1 mm). Figure 1. Open in new tabDownload slide Location of the study area and sampling sites for Penaeus semisulcatus in Bushehr waters, Persian Gulf. Sex was determined, and the five-stage external characteristics system of ovarian development described by King (1995) was used to stage the female P. semisulcatus, as follows: Stage I: undeveloped—found only in young shrimp, ovaries small and translucent; Stage II: developing—ovaries larger, opaque, and yellowish, with scattered melanophores over the surface; Stage III: nearly ripe—ovaries larger and yellow to greenish; Stage IV: ripe—ovaries green, filling virtually the whole space among other organs; Stage V: spent—spawned ovaries flabby and mud coloured, and microscopic examination is generally required to determine the stage accurately. The percentages of stages III (nearly ripe) and IV (ripe) female P. semisulcatus caught each month were calculated and recorded, to estimate the spawning season. The months with the highest percentages were defined as the spawning period. The presence of mature females (>50% at stages III and IV) during the peak spawning season in the various areas was used to define the main spawning grounds. The minimum size at maturity was calculated by comparing ovary maturation stage with CL. The length-at-50%-maturity (L50% or Lm) was determined according to the method of King (1995). The sex ratio was determined by counting the numbers of males and females taken monthly and confirmed by Chi-squared (χ2) test, as per the formula (Rees, 1991): where O is the observed frequency and E the expected frequency. Results Spawning season and size at maturity Penaeus semisulcatus spawning peaked in winter (December) and in early spring (March), but with a minor peak in autumn (October; Figure 2). The minimum abundance (11.5%) of mature females (stages III and IV) was in July (80% was stage I at that time). In contrast, some 91% of mature females were at stage III or IV during March, the balance of 9% then being recorded as stage II (Table 1). Therefore, we conclude that the spawning activity of P. semisulcatus in the Bushehr area peaks in December, decreases slightly from January to February, peaks again in March, and is then followed by a decrease in the proportion of mature females. Figure 2. Open in new tabDownload slide Percentage of Penaeus semisulcatus mature females (stages III and IV) in Bushehr waters, Persian Gulf, 2003/2004. Table 1. Monthly percentage of ovarian development stages for Penaeus semisulcatus in Bushehr waters, Persian Gulf, 2003/2004. Sampling month . Percentage per ovarian development stage . Total number . . I . II . III . IV . V . . January 2003 18 32 33 17 – 159 February 2003 7 15 27 49 2 100 March 2003 – 9 27 64 – 147 April 2003 6.5 20 49 24.5 – 45 May 2003 9 29 30 31 1 110 June 2003 53.5 12 17 16.5 1 199 July 2003 80 8.5 7.5 4 – 5 175 August 2003 65.5 10.5 11 12 1 2 292 September 2003 54 21.5 16 8 0.5 1 135 October 2003 30 27.5 26 14.5 2 814 November 2003 34.5 15.5 11.5 11.5 27 410 December 2003 – 14 35 43 8 134 January 2004 13 8 13 52 14 96 February 2004 24 19 33 14 10 44 March 2004 – 28.5 43 28.5 – 22 Sampling month . Percentage per ovarian development stage . Total number . . I . II . III . IV . V . . January 2003 18 32 33 17 – 159 February 2003 7 15 27 49 2 100 March 2003 – 9 27 64 – 147 April 2003 6.5 20 49 24.5 – 45 May 2003 9 29 30 31 1 110 June 2003 53.5 12 17 16.5 1 199 July 2003 80 8.5 7.5 4 – 5 175 August 2003 65.5 10.5 11 12 1 2 292 September 2003 54 21.5 16 8 0.5 1 135 October 2003 30 27.5 26 14.5 2 814 November 2003 34.5 15.5 11.5 11.5 27 410 December 2003 – 14 35 43 8 134 January 2004 13 8 13 52 14 96 February 2004 24 19 33 14 10 44 March 2004 – 28.5 43 28.5 – 22 “–”, none found in sample. Open in new tab Table 1. Monthly percentage of ovarian development stages for Penaeus semisulcatus in Bushehr waters, Persian Gulf, 2003/2004. Sampling month . Percentage per ovarian development stage . Total number . . I . II . III . IV . V . . January 2003 18 32 33 17 – 159 February 2003 7 15 27 49 2 100 March 2003 – 9 27 64 – 147 April 2003 6.5 20 49 24.5 – 45 May 2003 9 29 30 31 1 110 June 2003 53.5 12 17 16.5 1 199 July 2003 80 8.5 7.5 4 – 5 175 August 2003 65.5 10.5 11 12 1 2 292 September 2003 54 21.5 16 8 0.5 1 135 October 2003 30 27.5 26 14.5 2 814 November 2003 34.5 15.5 11.5 11.5 27 410 December 2003 – 14 35 43 8 134 January 2004 13 8 13 52 14 96 February 2004 24 19 33 14 10 44 March 2004 – 28.5 43 28.5 – 22 Sampling month . Percentage per ovarian development stage . Total number . . I . II . III . IV . V . . January 2003 18 32 33 17 – 159 February 2003 7 15 27 49 2 100 March 2003 – 9 27 64 – 147 April 2003 6.5 20 49 24.5 – 45 May 2003 9 29 30 31 1 110 June 2003 53.5 12 17 16.5 1 199 July 2003 80 8.5 7.5 4 – 5 175 August 2003 65.5 10.5 11 12 1 2 292 September 2003 54 21.5 16 8 0.5 1 135 October 2003 30 27.5 26 14.5 2 814 November 2003 34.5 15.5 11.5 11.5 27 410 December 2003 – 14 35 43 8 134 January 2004 13 8 13 52 14 96 February 2004 24 19 33 14 10 44 March 2004 – 28.5 43 28.5 – 22 “–”, none found in sample. Open in new tab Fewer than 5% of female P. semisulcatus of <24 mm CL were mature (stages III and IV), but the proportion of mature prawns increased rapidly with size (Figure 3). Therefore, 24 mm CL was taken to be the length at first sexual maturity. The length-at-50%-maturity (40 mm CL here; Figure 3) is a useful indicator of spawning activity for management purposes, at least when assessed during the seasons of large-scale spawning. The maximum proportion of sexually mature females in the samples was ∼86% at 54 mm CL (Figure 4). Figure 3. Open in new tabDownload slide Proportion of sexually mature female Penaeus semisulcatus at size (CL, in mm) in the Bushehr population of the Persian Gulf, 2003/2004. Figure 4. Open in new tabDownload slide Relationship between ovary maturation (stages III and IV) of Penaeus semisulcatus and CL (mm) in Bushehr waters, Persian Gulf, 2003/2004. Spawning areas and sex ratio In all, 1607 mature P. semisulcatus were sampled in the five spawning areas we found between January 2003 and March 2004 (Table 2). These five areas included 65% of the total number of mature prawns caught during the spawning periods. The maximum and minimum numbers caught in those periods were 46 and 34 in the Ganaveh and Helaileh waters, respectively. Mean density was 324 (s.d. 28.2; Table 2, Figure 5). Five locations in the northern and central sections of the study area had a relatively high density of adult, mature P. semisulcatus (Figure 5). Figure 5. Open in new tabDownload slide Spawning grounds of Penaeus semisulcatus in Bushehr waters, Persian Gulf, 2003/2004. Table 2. Number of mature female Penaeus semisulcatus (stages III and IV) in the spawning areas during the spawning season in Bushehr waters, Persian Gulf, 2003/2004. Spawning area . 2003 . 2004 . Total . Mean per month . . January . February . March . April . December . January . February . March . . . Imam Hassan 36 38 59 44 50 39 38 39 343 43 Ganaveh 40 47 65 32 51 49 40 43 367 46 Helleh 27 45 64 39 41 40 31 45 332 42 Helaileh 25 31 56 21 51 31 25 33 273 34 Rostami 30 29 58 28 49 27 29 42 292 37 All areas 1 607 321 Spawning area . 2003 . 2004 . Total . Mean per month . . January . February . March . April . December . January . February . March . . . Imam Hassan 36 38 59 44 50 39 38 39 343 43 Ganaveh 40 47 65 32 51 49 40 43 367 46 Helleh 27 45 64 39 41 40 31 45 332 42 Helaileh 25 31 56 21 51 31 25 33 273 34 Rostami 30 29 58 28 49 27 29 42 292 37 All areas 1 607 321 Open in new tab Table 2. Number of mature female Penaeus semisulcatus (stages III and IV) in the spawning areas during the spawning season in Bushehr waters, Persian Gulf, 2003/2004. Spawning area . 2003 . 2004 . Total . Mean per month . . January . February . March . April . December . January . February . March . . . Imam Hassan 36 38 59 44 50 39 38 39 343 43 Ganaveh 40 47 65 32 51 49 40 43 367 46 Helleh 27 45 64 39 41 40 31 45 332 42 Helaileh 25 31 56 21 51 31 25 33 273 34 Rostami 30 29 58 28 49 27 29 42 292 37 All areas 1 607 321 Spawning area . 2003 . 2004 . Total . Mean per month . . January . February . March . April . December . January . February . March . . . Imam Hassan 36 38 59 44 50 39 38 39 343 43 Ganaveh 40 47 65 32 51 49 40 43 367 46 Helleh 27 45 64 39 41 40 31 45 332 42 Helaileh 25 31 56 21 51 31 25 33 273 34 Rostami 30 29 58 28 49 27 29 42 292 37 All areas 1 607 321 Open in new tab The number of adults decreased in the southern part of the study area. During the main spawning season, the numbers of adult P. semisulcatus were greatest in the Imam Hassan, Ganaveh, Helleh, Helaileh, and Rostami areas. The numbers of adult females caught from 51°30′E 27°39′N to 51°57′E 27°45′N were lowest inshore and offshore (Figure 5). Adult P. semisulcatus aggregations were observed in 10–40 m of water, but the greatest abundance was found in 20–30 m. The P. semisulcatus sex composition in trawl samples varied monthly, but with an overall average male/female ratio of 0.84 (Table 3). Chi-squared (χ2) tests gave 0.0 (∝ = 0.05) for both sexes, indicating that the ratio of males to females was not significantly different. Table 3. Sex ratio (male/female) of P. semisulcatus in Bushehr waters, Persian Gulf, 2003/2004. Month . Total number caught . Males . Females . Sex ratio (M/F) . January 291 132 159 0.83 February 182 82 100 0.82 March 236 89 147 0.6 April 84 39 45 0.87 May 203 93 110 0.85 June 386 187 199 0.94 July 9 934 4 759 5 175 0.92 August 3 842 1 550 2 292 0.67 September 2 398 1 263 1 135 1.11 October 1 224 410 814 0.5 November 734 324 410 0.79 December 172 38 134 0.28 January 160 64 96 0.67 February 128 84 44 1.9 March 68 46 22 2 All months 20 042 9 160 10 882 0.84 Month . Total number caught . Males . Females . Sex ratio (M/F) . January 291 132 159 0.83 February 182 82 100 0.82 March 236 89 147 0.6 April 84 39 45 0.87 May 203 93 110 0.85 June 386 187 199 0.94 July 9 934 4 759 5 175 0.92 August 3 842 1 550 2 292 0.67 September 2 398 1 263 1 135 1.11 October 1 224 410 814 0.5 November 734 324 410 0.79 December 172 38 134 0.28 January 160 64 96 0.67 February 128 84 44 1.9 March 68 46 22 2 All months 20 042 9 160 10 882 0.84 Open in new tab Table 3. Sex ratio (male/female) of P. semisulcatus in Bushehr waters, Persian Gulf, 2003/2004. Month . Total number caught . Males . Females . Sex ratio (M/F) . January 291 132 159 0.83 February 182 82 100 0.82 March 236 89 147 0.6 April 84 39 45 0.87 May 203 93 110 0.85 June 386 187 199 0.94 July 9 934 4 759 5 175 0.92 August 3 842 1 550 2 292 0.67 September 2 398 1 263 1 135 1.11 October 1 224 410 814 0.5 November 734 324 410 0.79 December 172 38 134 0.28 January 160 64 96 0.67 February 128 84 44 1.9 March 68 46 22 2 All months 20 042 9 160 10 882 0.84 Month . Total number caught . Males . Females . Sex ratio (M/F) . January 291 132 159 0.83 February 182 82 100 0.82 March 236 89 147 0.6 April 84 39 45 0.87 May 203 93 110 0.85 June 386 187 199 0.94 July 9 934 4 759 5 175 0.92 August 3 842 1 550 2 292 0.67 September 2 398 1 263 1 135 1.11 October 1 224 410 814 0.5 November 734 324 410 0.79 December 172 38 134 0.28 January 160 64 96 0.67 February 128 84 44 1.9 March 68 46 22 2 All months 20 042 9 160 10 882 0.84 Open in new tab Discussion The time of spawning and recruitment (i.e. the time of the year) and the mean length, or age, at which these events happen are important to fisheries studies, particularly the cycle of events leading to reproduction and the timing of gamete release. In this study, the percentage of actively spawning P. semisulcatus was highest during late winter and early spring, peaking in March but with a secondary peak in December (Figure 2). In general, therefore, spawning activity varied seasonally, with a bimodal pattern of a dominant winter/spring peak and a lesser peak in autumn. After 6–7 months of autumn and winter/spring spawning, recruitment takes place in summer. Based on stock abundance, the shrimp fishing season lasts for some 6–8 weeks each summer, so the major recruitment fishery in summer is derived from two periods of spawning activity, on a 1-year-old group and a 6–7-month-old group. A double-peak pattern of reproductive activity appears to be typical for penaeid prawns. Garcia (1985) reviewed the seasonal spawning patterns of several penaeids and found the double-peak pattern to be the most common. In the Gulf of Carpentaria, Australia, Rothlisberg and Jackson (1987) found a bimodal seasonal pattern of abundance of larval P. semisulcatus, Fenneropenaeus merguiensis, and P. latisulcatus. For F. merguiensis in the Gulf of Carpentaria, Crocos and Kerr (1983) reported a bimodal pattern of seasonal egg production. Moreover, Crocos (1987) reported that the basic pattern of spawning for P. semisulcatus in the Gulf of Carpentaria was characterized by an initial spawning when the first individuals of a cohort breed at ∼6 months old, followed by a massive spawning at about 10–12 months old. Buckworth (1985) pooled data for P. semisulcatus from commercial catch samples taken over a 4-year period from the whole of the western Gulf of Carpentaria and used the monthly percentage of females with visible ovaries as an indicator of spawning activity. In contrast to other studies, Buckworth's (1985) results indicate a unimodal pattern of spawning activity extending over a prolonged period. For P. semisulcatus in the western Persian Gulf, Van Zalinge (1984) noted two spawning peaks annually, one in spring and one in autumn. The peaks varied in relative intensity from year to year, although generally the spring peak was the more important. Recruitment in autumn apparently stems from spring spawning, and spring recruitment from autumn spawning. In this study, the age at first spawning was about 12 months for most P. semisulcatus. Siddeek et al. (2001) reported that the peak spawning season of P. semisulcatus in waters of Oman was from November to December. Although gonad development and subsequent spawning depend on various environmental conditions, prawns must reach a certain age or size before they are capable of reproducing. The mean length at first spawning or mean length at sexual maturity is generally defined as the length at which 50% of females in a stock are sexually mature (40 mm CL in our study). The L50% for female P. semisulcatus in the Bushehr area was estimated by King (1995) to be 15.7 cm total length, i.e. 35 mm CL. The estimated L50% for P. semisulcatus in the Gulf of Carpentaria is 39 mm CL (Crocos, 1987). However, the estimated values of L50% reported by King (1995) and Crocos (1987) were not that different considering the geographic and temporal separation of the two studies. Fishing pressure can reduce the size of target species and the size at maturity, but this anthropogenic influence apparently has a lesser effect on short-lived species such as crustaceans or cephalopods (Sparre and Venema, 1992). Crocos (1987) reported the length at first maturity of female P. semisulcatus to be 29 mm CL and the length at 50% maturity to be 39 mm CL, or 13.4 and 17.2 cm total length, respectively. Major spawning peaks in the Crocos (1987) study were in August/September (spring) and February (early autumn). Buckworth (1985) reported that 20% of female P. semisulcatus were mature at 35 mm CL. From our results, we believe that the P. semisulcatus spawned in autumn contribute to the spring spawning, effectively splitting the generation time, first to the time of initial spawning (in autumn), which can be as early as 6–7 months old, and second to the peak spawning period of the parents (spring), which corresponds to prawns 1 year old. Variation in the reproductive output of P. semisulcatus as a consequence of season and age was evaluated by Crocos and Coman (1997). They measured the rates of maturation, spawning, fecundity, hatching, and early larval survival of prawns caught every second month for 14 months, and found that larval production increased between 6 and 12 months of age but declined in 14-month-old prawns. They noted 45% decline in larval production between 12 and 14 months, principally because of fewer spawnings per female, slightly lower hatch rates, and reduced rates of metamorphosis to the first protozoa. As this trend was apparent in both spring and autumn spawning cohorts, they considered it to be age related and not the result of differences in seasonal growth or other maturation factors. Somers and Kirkwood (1991) reported that natural mortality increases as penaeid prawns senesce. In wild populations, the largest females (>55 mm CL) were reproductively senescent and did not contribute to egg production (Courtney et al., 1995). Moreover, Crocos (1987) reported that seasonal egg production and fecundity of each female P. semisulcatus was more important than the total number of females each year. Dall et al. (1990) noted that there was a fishing-induced effect on the main recruitment levels within the study area through harvesting in the period August/September. Crocos and van der Velde (1995) assessed the reproductive dynamics of P. semisulcatus in Albatross Bay, Australia, using a population fecundity index (PFI) based on the abundance and fecundity of spawners. The population dynamics of that study were complex, with up to three cohorts of adult prawns at different ages (6, 12, and 18 months) recruiting to the fishery then moving into, out of, and back into the study area. The resultant patterns of reproductive output from all three cohorts (as measured by the PFI) showed, on average, a broad peak from August to February in their study area. Crocos and Coman (1997) noted that tropical penaeids typically live for ∼18 months and have two main spawning periods, when the females reach first maturity at ∼6 months, and again at ∼12 months old. The resultant recruitment from these spawning events produces a complex size and age composition for the population (at any one time), as a consequence of the overlapping generations. Spent individuals were not present in the fishery after the spawning season, suggesting that adults die soon after spawning. Reproduction and recruitment are critical events in the life history of a marine species. In some cases, these events involve migration between different areas. Some species migrate to spawning areas, and many species prefer certain habitats where their juveniles live and grow (King, 1995). Most adult P. semisulcatus live offshore, and most reports indicate that penaeids spawn in deep water. Yimin and Mohammad (1999) stated that P. semisulcatus is the dominant shrimp species in the central and southern waters of Kuwait. It is quite possible that some of the larvae and juveniles of P. semisulcatus spawned in northern Iranian waters move into the shallower waters of Kuwait, i.e. that the populations of P. semisulcatus in Iranian and Kuwait waters are a single stock, and that they should be managed as such. The results of this study in Bushehr waters have shown the existence of six main spawning grounds for P. semisulcatus. Clearly, the species would be managed more sustainably if these areas were to be afforded some protection, an important consideration for this highly valuable commercial species. Overexploiting the spawning stock will inevitably reduce the reproductive output and, in turn, production from the fishery. The current moratorium on exploiting P. semisulcatus in Bushehr waters is intended to protect the stock. However, the current management models assume a single cohort of spawning and recruitment, but it is now apparent that there are two spawning peaks in the area. The most important consequence of the existence of a one-catch season in the area is that heavily exploiting the main generation may drastically decrease their abundance before the next spawning season. Spring spawning generates new recruits in autumn, whereas winter spawning introduces new recruits to the fishery during summer. As stated above, Bushehr waters are the main fishing ground for P. semisulcatus in Iranian waters of the Persian Gulf. Exploiting this species during its spawning season has the effect of reducing reproductive output during a stage of its life history critical for stock renewal. Overexploiting a spawning stock will likely reduce reproductive output, which then becomes a limiting factor for production in the fishery. Therefore, managers and decision-makers need to note that in short-lived species such as prawns, controlling the spawning grounds and restricting access to them is a crucial means of protecting, managing, and sustainably utilizing the resource. Acknowledgements We thank the Director and staff of the Department of Biology, Faculty of Science, Universiti Putra Malaysia, for help and support during our work there. The project was funded by the Iranian Fisheries Research Organization (IFRO). We also thank IFRO and especially the stock assessment division of the Iran Shrimp Research Centre (ISRC) for their assistance in data collection, and the captain and crew of RV “Lavar II” for support during field sampling. Finally we thank J. Hoolihan, B. J. Gallaway, J. Browder, and M. Aktas for their valued reviews of early drafts of the manuscript. References Abdulqader E. A. A. . Bahrain shrimp fishery and the marine environment , Arab Gulf Journal of Scientific Research , 1999 , vol. 20 (pg. 165 - 174 ) Google Scholar OpenURL Placeholder Text WorldCat Azimi A. . Final report on shrimp resources survey project in the Persian Gulf, Bushehr waters , 1985 Persian Gulf Fisheries Research Center pg. 35 Google Scholar Boerema L. K. . The shrimp resources in the Gulf between Iran and the Arabian Peninsula , 1969 FAO Fisheries Circular, 310 pg. 29 Google Scholar Buckworth R. C. . Rothlisberg P. C. , Hill B. J. , Staples D. J. . Preliminary results of a study of commercial catches, spawning and recruitment of Penaeus esculeatus and Penaeus semisulcatus in the western Gulf of Carpentaria , Second Australian National Prawn Seminar, NPS2 , 1985 Cleveland, Australia CSIRO (pg. 213 - 270 ) Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC Courtney A. J. , Montgomery S. S. , Die D. J. , Andrew N. L. , Cosgrove M. G. , Blount C. . Maturation in the female eastern king prawn, Penaeus plebejus from coastal waters of eastern Australia, and considerations for quantifying egg production in penaeid prawns , Marine Biology , 1995 , vol. 122 (pg. 547 - 556 ) Google Scholar Crossref Search ADS WorldCat Crocos P. J. . Rothlisberg P. C. , Hill B. J. , Staples D. J. . Appraisal of some factors relevant to the development of penaeid prawn population reproductive models , Second Australian National Prawn Seminar, NPS2 , 1985 Cleveland, Australia CSIRO (pg. 159 - 164 ) Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC Crocos P. J. . Reproductive dynamics of the grooved tiger prawn, Penaeus semisulcatus in the northwestern Gulf of Carpentaria, Australia , Australian Journal of Marine and Freshwater Research , 1987 , vol. 38 (pg. 79 - 90 ) Google Scholar Crossref Search ADS WorldCat Crocos P. J. , Coman G. J. . Seasonal and age variability in the reproductive performance of Penaeus semisulcatus broodstock: optimising brood stock selection , Aquaculture , 1997 , vol. 155 (pg. 55 - 67 ) Google Scholar Crossref Search ADS WorldCat Crocos P. J. , Kerr Y. D. . Maturation and spawning of the banana prawn, Penaeus merguiensis (De Man), in the Gulf of Carpentaria, Australia , Journal of Experimental Marine Biology and Ecology , 1983 , vol. 69 (pg. 37 - 59 ) Google Scholar Crossref Search ADS WorldCat Crocos P. J. , van der Velde T. D. . Seasonal, spatial and interanvual variability in the reproductive dynamics of the groove tiger prawn, Penaeus semisulcatus, in Albatross Bay, Gulf of Carpentaria, Australia. The concept of effective spawning , Marine Biology , 1995 , vol. 122 (pg. 557 - 570 ) Google Scholar Crossref Search ADS WorldCat Dall W. , Hill B. J. , Rothlisberg P. C. , Staples D. J. . The biology of Penaeidae , Advances in Marine Biology , 1990 , vol. 27 (pg. 282 - 306 ) Google Scholar OpenURL Placeholder Text WorldCat Garcia S. . Rothlisberg P. C. , Hill B. J. , Staples D. J. . Reproduction, stock assessment models and population parameters in exploited penaeid shrimp populations , Second Australian National Prawn Seminar, NPS2 , 1985 Cleveland, Australia CSIRO (pg. 139 - 158 ) Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC Ghasemi S. , Niamaimandi N. . Biological parameters of Penaeus semisulcatus at different depths of the Persian Gulf, Iranian waters , 1994 Tehran Iranian Fisheries Research Organization pg. 83 (in Persian) Google Scholar Khorshidian K. . Biological characteristics of commercially exploited Penaeidae shrimp (Penaeus semisulcatus) in the north-western part of the Persian Gulf , 2002 The United Nations University Fishing Training Programme pg. 41 Google Scholar King M. . Fisheries Biology, Assessment and Management , 1995 Oxford, UK Oxford University Press pg. 342 Google Scholar Niamaimandi N. . Population dynamics of shrimp, Penaeus semisulcatus in the Persian Gulf, Bushehr waters , 1997 Tehran Iranian Fisheries Research Organization pg. 62 (in Persian) Google Scholar Penn J. W. . Spawning and fecundity of the western king prawn, Penaeus latisulcatus Kishinouye, in Western Australian waters , Australian Journal of Marine and Freshwater Research , 1980 , vol. 31 (pg. 21 - 35 ) Google Scholar Crossref Search ADS WorldCat Rees D. G. . Essential Statistics , 1991 2nd edn London Chapman and Hall pg. 256 Google Scholar Rothlisberg P. C. , Jackson C. J. . Larval ecology of penaeids in the Gulf of Carpentaria, Australia , Australian Journal of Marine and Freshwater Research , 1987 , vol. 38 (pg. 19 - 28 ) Google Scholar Crossref Search ADS WorldCat Sakurai T. . Fisheries of Saudi Arabia. Report of the Ministry of Agriculture and Water Department of Marine Fisheries, and Japan International Cooperation Agency , 1998 pg. 48 Google Scholar Siddeek M. S. M. , Hermosa G. , Al-Amri A. , Al-Aisery A. . Stock assessment of shrimp in the Gulf of Masirah, Sultanate of Oman , Proceedings of the First International Conference on Fisheries, Aquaculture and Environment in the NW Indian Ocean , 2001 Oman Sultan Qaboos University (pg. 107 - 118 ) Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC Somers I. F. , Kirkwood G. P. . Population ecology of the grooved tiger prawn, Penaeus semisulcatus, in the north-western Gulf of Carpentaria, Australia , Australiain Journal of Marine and Freshwater Research , 1991 , vol. 42 (pg. 349 - 367 ) Google Scholar Crossref Search ADS WorldCat Sparre P. , Venema S. C. . Introduction to tropical fish stock assessment. Part 1 , 1992 pg. 376 Manual. FAO Fisheries Technical Paper, 306/1 Rev. 1 Google Scholar Van Zalinge N. P. . Gulland J. A. , Rothschild B. J. . The shrimp fisheries in the Gulf between Iran and the Arabian Peninsula , Penaeid Shrimps—Their Biology and Management , 1984 Farnham, UK Fishing Book News (pg. 71 - 82 ) Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC Ye Y. , Al-Foudari H. M. , Bishop J. M. . Shrimp resources and fisheries in Kuwait waters , 1999 Kuwait Institute for Scientific Research, Report 5473 pg. 50 Google Scholar Yimin Y. , Mohammad H. M. A. . An analysis of variation in catchability of green tiger prawn, Penaeus semisulcatus, in waters off Kuwait , Fishery Bulletin US , 1999 , vol. 97 (pg. 702 - 712 ) Google Scholar OpenURL Placeholder Text WorldCat © 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. For Permissions, please email: [email protected] © 2008 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. For Permissions, please email: [email protected]

Smith, I. Philip; Jensen, Antony C.

doi: 10.1093/icesjms/fsn170pmid: N/A

Smith, I. P., and Jensen, A. C. 2008. Dynamics of closed areas in Norway lobster fisheries. ICES Journal of Marine Science, 65: 16001609.A dynamic, age-structured population model was developed to investigate the potential effects of introducing a closed area to a fishery for a species with limited adult mobility and planktonic dispersal of larvae, using biological and fishery information from a Norway lobster fishery in eastern Scotland. Simulated closure of part of the fishing grounds led to a long-term increase in total biomass and recruitment to the fished zone, but the larval subsidy did not compensate for the loss of fishing ground, and fishery yield was reduced under all modelled combinations of closed-area size and prior fishing effort. Concentration of effort in the fished zone and increased recruitment there led to reduced average size, and therefore value, of animals in the catch, as well as increased destruction of biomass by discarding undersized lobsters. Implementation of a closed area also led to oscillations in stock biomass, recruitment, and yield over several years after the closure, particularly with large closed areas and high fishing effort.

Wells, R. J. David; Cowan, James H.; Patterson, William F.

doi: 10.1093/icesjms/fsn145pmid: N/A

Wells, R. J. D., James H. Cowan Jr, and William F. Patterson III. 2008. Habitat use and the effect of shrimp trawling on fish and invertebrate communities over the northern Gulf of Mexico continental shelf. ICES Journal of Marine Science, 65: 16101619.The goals of this study were to characterize habitat-specific fish and invertebrate community structure over sand, shell-rubble, and natural reef substrata, and to assess the effects of trawling on the sand and shell-rubble habitats and their associated communities during quarterly trawl surveys over a 2-year period. Fish and invertebrate communities differed significantly among habitat types [analysis of similarities (ANOSIM); Global R 0.436, p < 0.001), and with respect to trawling exposure (ANOSIM; Global R 0.128, p < 0.001). Habitat characteristics were quantified from video transects sampled with a remotely operated vehicle, and included percentage coverage of tubeworms, bryozoans, anemones, corals, and algae, significantly affecting fish community structure. Diversity indices differed among habitats, with the highest Shannon diversity (H) and Pielou's evenness (J) over shell-rubble, specifically non-trawled shell-rubble. In addition, higher values of H and J were found over trawled sand relative to non-trawled sand habitats. Length frequency distributions of several abundant fish species showed truncated size distributions over trawled and non-trawled habitats and were both habitat- and species-specific. The study describes habitat-specific differences in community structure, highlighting the differences between trawled and non-trawled areas on the northern Gulf of Mexico continental shelf.

Als, Josep

doi: 10.1093/icesjms/fsn151pmid: N/A

Als, J. 2008. Influence of anatomical hooking depth, capture depth, and venting on mortality of painted comber (Serranus scriba) released by recreational anglers. ICES Journal of Marine Science, 65: 16201625.Immediate (45 h) and delayed (10 d) hooking mortality for released fish kept in tanks was evaluated for painted comber (Serranus scriba) taken by the recreational fishery of the Balearic Islands (western Mediterranean). Results showed low rates of immediate (10.8%) and delayed (3.3%) hooking mortality, a total mortality of 14.1%. Anatomical hook location and capture depth were the most significant predictors of mortality; 70.4% of fish caught with a deep location of hook died as a consequence of the damage caused, bleeding, and long unhooking times. Fish caught in depths >16 m showed evidence of external barotrauma caused by rapid decompression, which increased the probability of death. The most common forms of barotrauma were swimbladder enlargement and stomach inversion. For fish vented with the aid of a hypodermic needle to extract excess gas, mortality was reduced by half. Factors such as surface temperature, fish size, and hook type (J hook vs. circle hook) could not explain the mortality of fish released into tanks. Therefore, the results confirm that a practice of catch-and-release (voluntary or mandatory) for S. scriba needs to be promoted among recreational anglers.

Hubley, P. Bradford; Amiro, Peter G.; Gibson, A. Jamie F.; Lacroix, Gilles L.; Redden, Anna M.

doi: 10.1093/icesjms/fsn129pmid: N/A

Hubley, P. B., Amiro, P. G., Gibson, A. J. F., Lacroix, G. L., and Redden, A. M. 2008. Survival and behaviour of migrating Atlantic salmon (Salmo salar L.) kelts in river, estuarine, and coastal habitat. ICES Journal of Marine Science, 65: 16261634.The downstream migration of 30 Atlantic salmon (Salmo salar) kelts tagged with acoustic transmitters was monitored using 26 underwater receivers at eight locations from April to October 2006 in the LaHave River and Estuary. In all, 27 tags were detected as they left the coastal environment by the middle of May, 5 weeks after release, indicating a possible 90 kelt survival to coastal departure. Two missing tags and one dropped tag were assumed to be attributable to natural mortality in the estuary. Migration time from release to the outermost coastal receivers 24 km below the tide limit took an average of 14 d, but varied from 3 to 32 d. Some 40 of the kelts lingered and were active in the lower estuary. Five kelts monitored with depth transmitters migrated mostly at the surface in all habitats, with occasional brief descent to the bottom. A consecutive spawning salmon returned after 79 d outside the outermost array. The low rate of returns is consistent with the historical repeat spawning schedule for this river, and more precisely documents the temporal and spatial habitat use of migrating kelts.