ICES Journal of Marine Science: Journal du Conseil

Forcada, Aitor; Valle, Carlos; Snchez-Lizaso, Jos L.; Bayle-Sempere, Just T.; Corsi, Fabio

doi: 10.1093/icesjms/fsp234pmid: N/A

Forcada, A., Valle, C., Snchez-Lizaso, J. L., Bayle-Sempere, J. T., and Corsi, F. 2010. Structure and spatio-temporal dynamics of artisanal fisheries around a Mediterranean marine protected area. ICES Journal of Marine Science, 67: 191203.Marine protected areas (MPAs) have been proposed and established throughout the world, but few studies have adequately assessed the spatial adaptations of fishers to the limitations imposed by their placement. The main objectives of this work were to identify and describe the characteristics of the artisanal fisheries around Tabarca Marine Reserve (western Mediterranean Sea) and to define their activity in space and time. Data were collected through questionnaires to fishers and onboard sampling. The artisanal fisheries were complex owing to the multispecific nature of the landings, the variety of gears involved, and their marked seasonality. All boats of the three harbours around the MPA were assessed, for a total of 32 boats. The fishers exploit 18 fishing grounds with eight gear types, for a total of 17 mtiers. Mullus trammelnet, Sepia trammelnet, and sparid longline are the most frequently used mtiers. The main factors determining the spatial distribution of the fishing effort are proximity to home harbour, habitat heterogeneity, and closeness to the MPA. Total fishing effort appeared slightly concentrated around the MPA, but each mtier showed different patterns of effort distribution. Although the sparid gillnet and the sparid longline concentrated along MPA boundaries, the Sepia trammelnet and the Mullus trammelnet did not.

Dvoretsky, Alexander G.; Dvoretsky, Vladimir G.

doi: 10.1093/icesjms/fsp243pmid: N/A

Dvoretsky, A. G., and Dvoretsky, V. G. 2010. Epifauna associated with an introduced crab in the Barents Sea: a 5-year study. ICES Journal of Marine Science, 67: 204214.Species composition, prevalence, intensity, and spatial distribution of macro-invertebrates colonizing the invasive red king crab (Paralithodes camtschaticus) in a typical bay of the Barents Sea, Dalnezelenetskaya Bay (depths 540 m), and adjacent deeper water (120180 m) were examined in the summers of 20042008. In all, 43 associated species were found on the crabs. The most common epibionts were Mytilus edulis (Bivalvia), Obelia spp. (Hydrozoa), and Circeis armoricana (Polychaeta). Symbiotic species included Ischyrocerus commensalis and Ischyrocerus anguipes (Amphipoda), Harmothoe imbricata (Polychaeta), and Johanssonia arctica (Hirudinea). There were no significant differences in the prevalence of infestation between male and female crabs. The prevalence of most of the common species was greater in crabs with old shells than in crabs with new shells. Infestation levels of J. arctica were higher in deeper than in shallow water, and M. edulis was less abundant in deep water. All species found on the crabs appear to be native to the Barents Sea. However, I. commensalis amphipods were not found at the site examined before the introduction of the red king crab, indicating that their distribution may have changed after association with this host species. Introduced hosts may well influence the distribution of rare native species.

Furusawa, Masahiko; Amakasu, Kazuo

doi: 10.1093/icesjms/fsp246pmid: N/A

Furusawa, M., and Amakusu, K. 2010. The analysis of echotrace obtained by a split-beam echosounder to observe the tilt-angle dependence of fish target strength in situ. ICES Journal of Marine Science, 67: 215230.A method of echotrace analysis (ETA), proposed by Furusawa and Miyanohana in 1988 utilizes successive echodata from an individual fish to obtain the target-strength (TS) pattern as a function of fish tilt angle and behaviour. The method can be applied to data from an echosounder with any beam configuration, single-, dual-, and split-beam. However, the method has not been applied rigorously to split-beam sounder data, which provide most comprehensive and accurate information. The aim of this work is to establish an accurate and practical ETA method for split-beam echosounder data. Although the basic theory had already been developed, some theoretical and practical enhancement was needed; smoothing of an echotrack by linear and quadratic regressions, correction for transducer motion, and comparison of an observed TS pattern with a prolate-spheroid theoretical model. The analysis starts from careful selection of a single echotrace on an echogram and ends with a composite display of results including a three-dimensional fish track and a TS pattern as a function of the tilt angle of the fish. The method was applied to typical echotrace examples, and utility and practicality were confirmed. A means of increasing the number of applicable echotraces is discussed.

Downey, Nicola J.; Roberts, Michael J.; Baird, Dan

doi: 10.1093/icesjms/fsp237pmid: N/A

Downey, N. J., Roberts, M. J., and Baird, D. 2010. An investigation of the spawning behaviour of the chokka squid Loligo reynaudii and the potential effects of temperature using acoustic telemetry. ICES Journal of Marine Science, 67: 231243.Spawning aggregations of chokka squid are influenced by environmental conditions. Acoustic telemetry was used to monitor the behaviour of spawning squid in relation to environmental variability. During the November squid-fishery closed seasons of 20032006, hexagonal VR2 receiver arrays were moored on and around active spawning aggregations in Kromme Bay, South Africa. In all, 45 squid were tagged (V9P-6L-S256 transmitters) and released within these arrays. Three presenceabsence behaviours were identified: (i) arrival on the spawning site at dawn and departure after dusk, (ii) continuous presence for a number of days, and (iii) presence interrupted by frequent but short periods of absence. Movement between spawning sites was both diurnal and nocturnal. Squid presence at the monitored sites increased after dawn and decreased towards and after dusk. Occasionally, a core aggregation of squid remained on the spawning sites at night. Temperature data at the sites indicated occasional upwelling, and although the role of temperature in the spawning process is not well understood, data suggest that it is linked to the continuation and or interruption of spawning after an aggregation has formed. The initial formation of spawning aggregations appears to be triggered by upwelling events.

Loots, Christophe; Vaz, Sandrine; Planque, Benjamin; Koubbi, Philippe

doi: 10.1093/icesjms/fsp238pmid: N/A

Loots, C., Vaz, S., Planque, B., and Koubbi, P. 2010. What controls the spatial distribution of the North Sea plaice spawning population? Confronting ecological hypotheses through a model selection framework. ICES Journal of Marine Science, 67: 244257.The spatial dynamics of spawning fish are crucial because they influence the survival rates of eggs and larvae and ultimately impact the reproductive success of populations. The factors that control these dynamics are complex and potentially many, and they interact. A model-selection-based approach was developed to confront various hypotheses of control of the spatial distribution of spawning population of North Sea plaice (Pleuronectes platessa). For each hypothesis or combination thereof, statistical models were constructed. These were then ranked and selected based on their ability to adjust and predict observed spatial distributions. The North Sea plaice population seems to have developed strong attachment to specific spawning sites, where geographic location and population memory are important controlling factors. Temporal changes in spatial distribution patterns appear to be influenced primarily by population size and demography. Variations in hydrographic conditions such as temperature and salinity do not appear to control interannual fluctuations in spatial distribution. This means that, for reproduction, applying conventional habitat models may falsely attribute major controlling effects to environmental conditions. It is concluded that a multiple-hypothesis approach is essential to understanding and predicting the present and future distribution of the North Sea plaice population during its spawning season.

Jardim, Ernesto; Cervio, Santiago; Azevedo, Manuela

doi: 10.1093/icesjms/fsp233pmid: N/A

Jardim, E., Cervio, S., and Azevedo, M. 2010. Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information. ICES Journal of Marine Science, 67: 258269.Iberian hake assessment revealed an increase in fishing mortality (F) despite enforcement of a recovery plan. Recent landings exceeded the total allowable catch and discarding rates were high. Alternative management strategies based on F control were evaluated with respect to the probability of recovering spawning-stock biomass (SSB), expected profits, and robustness to uncertainty on catch information and stock dynamics. Results showed that the use of censored catch data, i.e. excluding the Gulf of Cdiz or discards, may lead to inappropriate conclusions. Reducing fishing mortality was necessary for SSB to recover. An Fmax strategy with discard reduction showed the highest probability of rebuilding SSB and led the fishery to sustainable exploitation, with an expected SPR of 3040 in 2025, mean individual weight in the landings of 450 g in 2015, and yield increasing by >20. Because of uncertainty in the estimates of maximum sustainable yield, management strategies based on FMSY were least robust, but all strategies were robust to alternative stockrecruit models.

Desprez, M.; Pearce, B.; Le Bot, S.

doi: 10.1093/icesjms/fsp245pmid: N/A

Desprez, M., Pearce, B., and Le Bot, S. 2010. The biological impact of overflowing sands around a marine aggregate extraction site: Dieppe (eastern English Channel). ICES Journal of Marine Science, 67: 270277.The study investigates the physical impact of sediment deposition associated with aggregate dredging at a site off Dieppe, and the consequences for benthic fauna. Sampling stations were sited across potential zones of impact classified as high, moderate, and low deposition, depending on their proximity to dredging activities and their position relative to the net sediment transport route. Samples were also taken west of the dredge site outside the zone of likely impact (no deposition). A strong gradient was observed from the sediments dominated by fine sands in the high and moderate deposition zones, through to coarse sands and gravels in the low and no deposition zones. The benthic fauna sampled from the deposits of fine sand in the high and moderate deposition zones were sparse compared with the coarser deposits sampled from the low and no deposition zones. There was a strong correspondence between the distribution of different sediment fractions and the associated benthic fauna, with a weighted Spearman rank correlation of 0.638, higher than reported in related studies. This suggests that in deposition areas such as this, biological interactions play a less important role in shaping communities than the changes in the physical environment, which may have a greater impact on the biological communities.

Reiss, Henning; Degraer, Steven; Duineveld, Gerard C. A.; Krncke, Ingrid; Aldridge, John; Craeymeersch, Johan A.; Eggleton, Jacqueline D.; Hillewaert, Hans; Lavaleye, Marc S. S.; Moll, Andreas; Pohlmann, Thomas; Rachor, Eike; Robertson, Mike; Vanden Berghe, Edward;

de la Torriente, Ana; Quiones, Renato A.; Miranda-Urbina, Diego A.; Echevarra, Fidel

doi: 10.1093/icesjms/fsp235pmid: N/A

de la Torriente, A., Quiones, R. A., Miranda-Urbina, D. A., and Echevarra, F. 2010. South American sea lion and spiny dogfish predation on artisanal catches of southern hake in fjords of Chilean Patagonia. ICES Journal of Marine Science, 67: 294303.The South American sea lion (Otaria flavescens) is a pinniped known to interact with fisheries, potentially damaging gear and lowering catches. Predation by O. flavescens and spiny dogfish (Squalus acanthias) on artisanal southern hake (Merluccius australis) catches in fjords of Chilean Patagonia is estimated and compared. Observations were made in the Gulf of Ancud and Comau Fjord in southern Chile from October 2005 to September 2006. Losses of southern hake catches to O. flavescens predation were 1.6 of the total catch of the species, and to spiny dogfish predation were slightly higher, at 3.3. The predation of both species on southern hake catches varied throughout the year, but was lower in summer. Both predators showed a preference for adult southern hake over juveniles. There was no significant relationship between predation on southern hake catches by the sea lion and the availability of adult and juvenile southern hake on longlines (AHCL). However, there was a significant relationship (p < 0.05) between AHCL and spiny dogfish predation. Most O. flavescens interaction events (81.4) were during longline retrieval. Our results showed minimal interactions between O. flavescens and the artisanal southern hake fishery in the area, so with the present abundance of O. flavescens, there is no justification for reducing the sea lion population by hunting.

Sjare, Becky; Stenson, Garry B.

doi: 10.1093/icesjms/fsp267pmid: N/A

Sjare, B., and Stenson, G. B. 2010. Changes in the reproductive parameters of female harp seals (Pagophilus groenlandicus) in the Northwest Atlantic. ICES Journal of Marine Science, 67: 304315.Changes in female harp seal (Pagophilus groenlandicus) reproductive parameters from 1980 to 2004, and long-term trends since the early 1950s, are evaluated. Estimates of the total number of seals in the Northwest Atlantic declined from 3.0 million in the 1950s to 1.8 million in the early 1970s, then increased steadily to 5.5 million in 1996, at which relatively stable level it has remained since. Pregnancy rates increased from 86 in the 1950s to a high of 98 in the mid-1960s, then declined to 6570 by the early 1990s; the rate then varied between 45 and 70 from 2000 to 2004. Concurrently, the mean age at sexual maturity decreased from 5.8 (s.e 0.02) years in the mid-1950s to 4.1 (s.e. 0.02) in the late 1970s, increased to 5.5 (s.e. 0.03) years by the early 1990s, and peaked at 5.7 (s.e. 0.01) in 1995. From 2000 to 2004, mean age varied from 4.9 (s.e. 0.01) to 6.0 (s.e. 0.01) years. Although the direction of change in each of the parameters was consistent with a density-dependent response, changes in population size explained relatively little of the variability observed, suggesting that other ecological or environmental factors were influential.