ICES Journal of Marine Science: Journal du Conseil

Wakefield, Corey B.; Newman, Stephen J.; Marriott, Ross J.; Boddington, Dion K.; Fairclough, David V.

doi: 10.1093/icesjms/fst020pmid: N/A

Wakefield, C. B., Newman, S. J., Marriott, R. J., Boddington, D. K., and Fairclough, D. V. 2013. Contrasting life history characteristics of the eightbar grouper, Hyporthodus octofasciatus (Pisces: Epinephelidae), over a large latitudinal range reveals spawning omission at higher latitudes. – ICES Journal of Marine Science, 70: 485497.Demographic data on deep-water groupers are limited despite them being highly exploited throughout the Indo-Pacific. In Western Australia, the continuous distribution of the eightbar grouper, Hyporthodus octofasciatus, spans tropical to temperate waters over ∼3500 km from 12°S–35°S. The maximum age was markedly higher in the northern tropical waters than in southern temperate waters, i.e. 47 vs 20 years. Females attained a significantly larger length-at-age in southern temperate waters. Macroscopic and microscopic examination of gonads and annual trends in mean monthly gonadosomatic indices (GSIs) were used to determine that this monandric protogynous hermaphrodite spawns from late spring to summer (October–February) in northwestern Australia. In the temperate waters of WA, there was no evidence of reproduction and no males were observed south of ∼30°S latitude. The lengths at which 50% of female H. octofasciatus matured and changed sex were estimated from northern tropical populations at 560 mm (6.1 years) and 1022 mm (≥11 years). Although the population connectivity of H. octofasciatus is unknown, the spawning omission in temperate waters suggests recruitment from the northern tropical areas and highlights the importance of preserving spawning stocks in those northern waters.

Gasche, Loïc; Gascuel, Didier

doi: 10.1093/icesjms/fst016pmid: N/A

Gasche, L., and Gascuel, D. 2013. EcoTroph: a simple model to assess fishery interactions and their impacts on ecosystems – ICES Journal of Marine Science, 70: 498510.The EcoTroph model leaves aside the notion of species, and models the functioning of marine ecosystems as flows of biomass from low to high trophic levels, so as to quantify easily the impacts of fishing at an ecosystem scale. In this paper, based on two case studies we present a new development of the EcoTroph model that is devoted to the analysis of fishery interactions and impacts of fleet segments on ecosystems. First, deriving an EcoTroph model from an Ecopath model of the Guinea ecosystem, the impacts of the artisanal fishery are distinguished from those of the industrial fishery. It appears that these fisheries do not always compete for the same fish groups but that they both strongly impact the ecosystem and moderately impact one another. Then, an EcoTroph model of the Southern Benguela ecosystem is set up, also based on a pre-existing Ecopath model. Two scenarios are simulated: a doubling in the fishing mortality of small pelagics and a doubling in the fishing mortality of hake. An increase in fishing mortality of small pelagics causes a strong decrease in biomass at all trophic levels of the ecosystem, confirming the pivotal role of these “wasp-waist” species in this ecosystem.

Bullimore, Ross D.; Foster, Nicola L.; Howell, Kerry L.

doi: 10.1093/icesjms/fss195pmid: N/A

Bullimore, R. D., Foster, N. L., and Howell, K. L. 2013. Coral-characterized benthic assemblages of the deep Northeast Atlantic: defining “Coral Gardens” to support future habitat mapping efforts – ICES Journal of Marine Science, 70: 511522.Providing statistically robust maps of habitat distributions on which to base spatial planning and management of the marine area is reliant upon established and agreed descriptions and definitions of habitats. “Coral Gardens” is an Oslo–Paris Convention (OSPAR) listed habitat, which currently cannot be reliably mapped as a result of poorly developed deep-sea habitat classification systems and habitat definitions. The aim of this study is to assess and inform development of the current definition of this habitat to support future mapping efforts. This study uses multivariate community analysis of video data to identify deep-sea benthic assemblages characterized by coral taxa and thus constituting a potential “coral gardens” habitat. Assemblages are assessed against a set of qualifying criteria, derived from current definitions of “coral gardens”, first at the assemblage level then sample by sample. The current definition of “coral gardens” captures a range of benthic assemblages, thus “Coral Gardens” cannot be considered a single “habitat”. While 19 assemblages are identified as being characterized by one or more coral garden taxa, only 8 meet the qualifying criteria. It is suggested that the current definition incorporates descriptions of the different “Coral Gardens” assemblages together with guidance on threshold densities for coral species specific to each assemblage type.

Gerritsen, Hans D.; Minto, Cóilín; Lordan, Colm

doi: 10.1093/icesjms/fst017pmid: N/A

Gerritsen, H. D., Minto, C., and Lordan, C. 2013. How much of the seabed is impacted by mobile fishing gear? Absolute estimates from Vessel Monitoring System (VMS) point data. – ICES Journal of Marine Science, 70: 523531.Demersal trawling impacts extensively on the seabed, and the extent and frequency of this impact can be assessed using Vessel Monitoring System (VMS) data (positional data of fishing vessels). Existing approaches interpolate fishing tracks from consecutive VMS locations (track interpolation) and/or aggregate VMS point data in a spatial grid (point summation). Track interpolation can be quite inaccurate with the current 2-hour time interval between VMS records, leading to biased estimates. Point summation approaches currently only produce relative estimates of impact and are highly sensitive to the grid size chosen. We propose an approach that provides absolute estimates of trawling impact from point data and is not sensitive to an arbitrary choice of grid-cell size. The method involves applying a nested grid and estimating the swept area (area covered by fishing gear) for each VMS point. We show that the ratio of the swept area to the surface area of a cell can be related to the proportion of the seabed that was impacted by the gear a given number of times. We validate the accuracy of this swept-area ratio approach using known vessel tracks and apply the method to international VMS data in the Celtic Sea.

Øresland, Vidar; Ulmestrand, Mats

doi: 10.1093/icesjms/fst019pmid: N/A

Øresland, V., and Ulmestrand, M. 2013. European lobster subpopulations from limited adult movements and larval retention. – ICES Journal of Marine Science, 70: 532539.Adults and larvae of the European lobster, Homarus gammarus, were studied within and around the Swedish Kåvra lobster reserve (2.2 km2). Tagging of 4016 lobsters within the reserve showed that the lobsters have limited movement out of the reserve. Only 58 lobsters (1.4% of all tagged lobsters) were recaptured ≥1 km from the reserve and 5658 recaptures were obtained inside the reserve. Light trap catches showed that stage 1 larvae had a peak occurrence during <2 weeks, in early August, 2007–2009. The mean depth distribution of stage 1 larvae was 16 m and very few larvae were found in the low saline surface layer. No later stages were found in horizontal net tows. The lobsters inside the reserve provided stage 1 larvae to the nearby area. A persistent retention of water masses was found at 16-m depth (below the sharp halocline) in the area (16 km2) around the reserve using IMR GPS Current Drifters. In sharp contrast, surface drifters showed strong offshore and inshore movements. The Swedish archipelago might harbour many lobster and other decapod subpopulations, if the larval stages occur in a large proportion below the sharp halocline and if adult movements are limited.

Lynam, Christopher P.; Halliday, Nicholas C.; Höffle, Hannes; Wright, Peter J.; van Damme, Cindy J. G.; Edwards, Martin; Pitois, Sophie G.

doi: 10.1093/icesjms/fst006pmid: N/A

Lynam, C. P., Halliday, N. C., Höffle, H., Wright, P. J., van Damme, C. J. G., Edwards, M., and Pitois, S. 2013. Spatial patterns and trends in abundance of larval sandeels in the North Sea: 1950–2005 – ICES Journal of Marine Science, 70: 540553.Early recruitment indices based on larval fish data from the Continuous Plankton Recorder (CPR) have the potential to inform stock assessments of Ammodytes marinus in the North Sea. We evaluate whether the CPR data are reliable for sandeel larvae. Spatially, CPR larval data were comparable with catches by dedicated larval samplers (Gulf and bongo nets) during ICES coordinated surveys in 2004 and 2009. ICES data are also used to explore environmental influences on sandeel distributions. Temporally, CPR data correlate with larval data from plankton surveys off Stonehaven (1999–2005), with sandeel 0-group trawl data at the east Fair Isle ground (since 1984), and with recruitment data (since 1983) for the Dogger Banks stock assessment area. Therefore, CPR data may provide an early recruit index of relative abundance for the Dogger Banks assessment area, where the majority of the commercial catch of A. marinus is taken, and the Wee Bankie area that is particularly important for seabird foraging. While warm conditions may stimulate the production of sandeel larvae, their natural mortality is typically greater, in the Dogger Banks and Wadden Sea areas, when the larvae are hatched in warm years and/or with abundant 1-year-old sandeel that are likely to be cannibalistic.

Benoît, Hugues P.

doi: 10.1093/icesjms/fss203pmid: N/A

Benoît, H. P. 2013. Two decades of annual landed and discarded catches of three southern Gulf of St Lawrence skate species estimated under multiple sources of uncertainty. – ICES Journal of Marine Science, 70: 554563.Estimating fishery impacts on commercially unimportant species is often hindered by limited and possibly biased data for landed and discarded catch, and poor information on discard mortality. The three skate (family Rajidae) species occurring in southern Gulf of St Lawrence (Canada) exemplify this problem. Assessing the contribution of fishing to important declines in their adult abundance has been complicated by catch data that are not disaggregated by species, concerns about the reliability of discard amounts estimated from fisheries observer surveys, and unknown discard mortality rates. An approach is presented for producing annual estimates of landed and discarded catch, as well as discard mortality rates, for the three species for the period 1991–2011. The approach used data from landing statistics and from observer surveys, and models for disaggregating mixed fishery catches into their constituent species and for estimating minimum discard mortalities. Bootstrapping was used to propagate errors associated with different components of the estimation process. The estimation was partly validated by comparing recorded landings with landings estimated from fisheries observer surveys. This paper demonstrates how multiple sources of uncertainty in discard loss estimation can be addressed by dividing the estimation process into linked components that can be individually addressed and ideally validated.

Pham, Christopher K.; Canha, Angela; Diogo, Hugo; Pereira, João G.; Prieto, Rui; Morato, Telmo

doi: 10.1093/icesjms/fst024pmid: N/A

Pham, C. K., Canha, A., Diogo, H., Pereira, J. G., Prieto, R., and Morato, T. 2013. Total marine fishery catch for the Azores (1950–2010). – ICES Journal of Marine Science, 70: 564577.Official fishery statistics often fail to report what has been truly extracted from the marine environment. Therefore, in this study, we estimated illegal, unreported, and unregulated (IUU) catch in the context of a small-scale fishery (the Azores) and provide an improved compilation of official catches, including whaling. Reconstructed removals during 1950–2010 total 1.10 million t (95% CI, 1.06–1.16 million t), a factor of 1.17 higher than the amount reported in Azorean official statistics. Unreported catches were attributed to foreign fishing activities (27%), recreational fishing (25%), discards from the demersal fishing fleet (21%), baitfish for the pole-and-line tuna fishery (11%), discards from pelagic longlining (7%), local pelagic fleet landing outside the Azores (3%), coastal invertebrate harvesting (6%), and big-game fishing (0.1%). The overall low level of unreported catches compared to other locations might reflect the small-scale nature of the fisheries, the geographic isolation of the islands, and the small size of its community.

Coll, Josep; Garcia-Rubies, Antoni; Morey, Gabriel; Reñones, Olga; Álvarez-Berastegui, Diego; Navarro, Oliver; Grau, Antoni M.

doi: 10.1093/icesjms/fst025pmid: N/A

Coll, J., Garcia-Rubies, A., Morey, G., Reñones, O., Álvarez-Berastegui, D., Navarro, O., and Grau, A. M. 2013. Using no-take marine reserves as a tool for evaluating rocky-reef fish resources in the western Mediterranean). - ICES Journal of Marine Science, 70: 578590.The use of MPAs to recover fish stocks in littoral areas of the western Mediterranean has made it possible to obtain time dataseries on the biomass evolution over the last decade. The biomass of six fully protected MPAs increased between two- and threefold over a period of five years. After this time the biomass remained stable. This pattern allowed us to adjust logistic curves between the biomass and protection time, and to estimate the carrying capacity (K) of each site. In the present study we investigate the relationships between carrying capacity (K) and habitat characteristics at each protected site. The relationships between habitat/environmental variables and K are analysed by applying generalized linear models. Environmental descriptors showing major effects on biomass are related to depth, exposure, rugosity, and offshore slope at different spatial scales. Comparison of observed and predicted values using the model for exploited sites in the Balearic Islands made it possible to determine their conservation status. This empirical approach to the relationships between environmental factors and fish assemblage biomass could constitute a very useful tool when traditional fishery management based on catch and effort data from the artisanal and recreational fleets is difficult to apply.

Hart, Deborah R.

doi: 10.1093/icesjms/fss204pmid: N/A

Hart, D. R. 2013. Quantifying the tradeoff between precaution and yield in fishery reference points. – ICES Journal of Marine Science, 70: 591603.A method using Monte Carlo simulations for estimating fishery reference points that accounts for parameter uncertainty is presented. Uncertainties in the input parameters of yield-per-recruit and stock-recruit analyses are propagated to estimate uncertainty in reference points such as FMSY. These uncertainties are used to evaluate the tradeoffs between the risks of overfishing and stock collapse, and the cost of reduced expected yield due to setting fishing mortality below FMSY. At fishing mortalities near FMSY, reduction in fishing mortality substantially decreases the probability of overfishing and stock collapse in exchange for slightly reduced expected yield. At lower fishing mortality rates, the marginal benefit (in terms of lessened risk of overfishing and stock collapse) from further reductions in fishing mortality is less, and the cost in forgone yield is greater. Less resilient “low steepness” stocks require additional precaution due to the risk of complete population collapse. Marine protected areas can also reduce risks of collapse, but at a higher cost in terms of expected yield than effort reduction. Implementation uncertainty (i.e. uncertainty in achieving a fishing mortality target) increases the risk of overfishing as well the loss of yield due to precaution, except at fishing mortalities near or above FMSY.