2015-07-29

Coastal Zones: Solutions for the 21st Century

Baztan J, Chouinard O, Jorgensen B, Tett P, Vanderlinden J-P, Vasseur L eds. Coastal Zones: Solutions for the 21st Century. Elsevier; 2015. Available from: http://www.elsevier.com/books/coastal-zones/baztan/978-0-12-802748-6
Freely available?: 
No
Summary available?: 
No
Type: Book

Coastal Zones: Solutions for the 21st Century bridges the gap between national and international efforts and the local needs for actions in communities where coastal zone challenges are faced daily. The solution-oriented approach covers issues of coastal zone management as well as responses to natural disasters. This work provides ideas on how to face the challenges, develop solutions, and localize management of common-pool resources.

Coastal Zones targets academic stakeholders and coastal stakeholders who have local knowledge and experience but need a theoretical framework and a greater range of skills to make use of this experience.

Efficacy of selective devices in reducing discards in the Nephrops trawl fishery in the Bay of Biscay

Nikolic N, Diméet J, Fifas S, Salaün M, Ravard D, Fauconnet L, Rochet M-J. Efficacy of selective devices in reducing discards in the Nephrops trawl fishery in the Bay of Biscay. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1869 - 1881. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv036
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

The Nephrops fishery in the Bay of Biscay is an important commercial fishery which generates large amounts of discards owing to the use of small mesh trawls. To reduce discards, French trawlers were equipped with a variety of selective devices, from 2005 onwards. This study examines their efficacy using data from the French on-board observer programme, 2003–2010. Generalized linear models were built for catches, discards, and landings of Nephrops and hake, controlling for the other factors which drive the variability in these variables. A dorsal square-mesh panel meant to let small hake escape did not affect hake catch, but was found to decrease Nephrops catches and discards. Among the devices intended to reduce Nephrops discards, the flexible grid was the most efficient, as it decreased catches and discards in large proportions while increasing landings but this result was supported by a small number of observations; a larger mesh size in the codend (80 mm instead of 70) slightly decreased Nephrops discards; and a ventral square-mesh panel was not found to affect catch or discards of either species. The design of the on-board observer programme was meant to estimate discard amounts, which limited their utilization to investigate factors for discarding.

A simple technical measure to reduce bycatch and discard of skates and sharks in mixed-species bottom-trawl fisheries

Kynoch RJ, Fryer RJ, Neat FC. A simple technical measure to reduce bycatch and discard of skates and sharks in mixed-species bottom-trawl fisheries. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1861 - 1868. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv037
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

Due to global declines, skates and sharks have become a focus of marine conservation in recent years. Despite protective measures, they remain vulnerable to bycatch by fisheries, especially bottom-trawls and pose a problem for fisheries management measures that aim to eliminate discards in the future. In the mixed-species bottom-trawl fisheries of the North Atlantic catches can be increased by fitting a length of chain known as a “tickler” in front of the groundgear of the trawl. It was hypothesized that the tickler is especially effective at catching skates and rays that may otherwise escape beneath the net. A trial was undertaken with paired tows with and without the tickler chain. The trial demonstrated that the catch rate of skates and sharks can be significantly lowered by removing the tickler. A set of secondary nets (groundgear bags) attached behind the groundgear of the main net allowed the number of fish escaping under the net to be estimated and showed that the reduction of skates and sharks in the main net was accompanied by an increase in number in the groundgear bags. This suggests that prohibition of the use of tickler chains in areas that are known to be especially important to skates and sharks could have conservation benefits. The removal of the tickler chain had little effect on catch rates of haddock, whiting, and flatfish, but caused a marked decrease in the catch rate of commercially valuable anglerfish.

Discarding of cod in the Danish Fully Documented Fisheries trials

Ulrich C, Olesen HJakob, Bergsson H, Egekvist J, Håkansson KBirch, Dalskov J, Kindt-Larsen L, Storr-Paulsen M. Discarding of cod in the Danish Fully Documented Fisheries trials. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1848 - 1860. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv028
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Denmark was the first nation in Europe to promote the use of Fully Documented Fisheries (FDF) through Remote Electronic Monitoring (REM) and CCTV camera systems, with pilot schemes in place since 2008. In theory, such a scheme could supplement and even potentially replace expensive control and monitoring programmes; and when associated with a catch quota management (CQM) system, incentivize positive changes in fishing patterns in a results-based management approach. New data flows are, however, required to ensure the practical implementation of such a scheme. This paper reviews the quality of the FDF data collected during 2008–2014 and their potential in strengthening information on cod discards. The analyses demonstrate the improved reporting of discards in logbooks and overall discard reductions, but they also show that some uncertainties around the absolute estimates of discard quantities have remained. Regular validation of weight estimation methods and close collaboration between scientific monitoring and control are important to support the use of reported discards as a reliable source of information. We discuss the potential of electronic monitoring in the context of the EU landing obligation.

A generalized model for longitudinal short- and long-term mortality data for commercial fishery discards and recreational fishery catch-and-releases

Benoît HP, Capizzano CW, Knotek RJ, Rudders DB, Sulikowski JA, Dean MJ, Hoffman W, Zemeckis DR, Mandelman JW. A generalized model for longitudinal short- and long-term mortality data for commercial fishery discards and recreational fishery catch-and-releases. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1834 - 1847. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv039
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

Conservation concerns and new management policies such as the implementation of ecosystem-based approaches to fisheries management are motivating an increasing need for estimates of mortality associated with commercial fishery discards and released fish from recreational fisheries. Traditional containment studies and emerging techniques using electronic tags on fish released to the wild are producing longitudinal mortality-time data from which discard or release mortalities can be estimated, but where there may also be a need to account analytically for other sources of mortality. In this study, we present theoretical and empirical arguments for a parametric mixture-distribution model for discard mortality data. We show, analytically and using case studies for Atlantic cod (Gadus morhua), American plaice (Hippoglossoides platessoides), and winter skate (Leucoraja ocellata), how this model can easily be generalized to incorporate different characteristics of discard mortality data such as distinct capture, post-release and natural mortalities, and delayed mortality onset. In simulations over a range of conditions, the model provided reliable parameter estimates for cases involving both discard and natural mortality. These results support this modelling approach, indicating that it is well suited for data from studies in which fish are released to their natural environment. The model was found to be less reliable in simulations when there was a delay in discard mortality onset, though such an effect appears only in a minority of existing discard mortality studies. Overall, the model provides a flexible framework in which to analyse discard mortality data and to produce reliable scientific advice on discard mortality rates and possibilities for mitigation.

Quantifying the projected impact of the South African sardine fishery on the Robben Island penguin colony

Robinson WML, Butterworth DS, Plagányi ÉE. Quantifying the projected impact of the South African sardine fishery on the Robben Island penguin colony. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1822 - 1833. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv035
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

Quantitative methods are needed to evaluate the ecological effects of fishing forage species upon which predators depend. African penguin Spheniscus demersus numbers at the Robben Island colony rose during the 1990s co-incidental with a marked increase in sardine Sardinops sagax and anchovy Engraulis encrasicolus abundances, but decreased appreciably during the 2000s as sardine suffered a series of poor recruitments. A population dynamics model is developed which relates penguin adult annual mortality to local sardine biomass, and is fit to penguin moult counts and re-sightings of tagged penguins. The predator–prey interaction is best explained by a sardine–penguin mortality relationship with average penguin survival decreasing only when the local sardine biomass is less than approximately one-quarter of the maximum observed. Results suggest that the rapid growth of the colony during the 1990s was driven primarily by immigration. Penguin projections are generated by linking to future sardine abundances predicted under the operational management procedure used to set catch limits for these sardine and anchovy fisheries, and compared with equivalent scenarios without fishing. Results indicate that fishing is likely to have a relatively small impact on penguins, especially when compared with uncertainties that arise from the variable spatial distribution of the sardine population.

Effects of baited crab pots on cultivated mussel (Mytilus edulis) survival rates

Calderwood J, O'Connor NE, Roberts D. Effects of baited crab pots on cultivated mussel (Mytilus edulis) survival rates. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1802 - 1810. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv043
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

The shore crab, Carcinus maenas, is recognized as a voracious predator of blue mussels, Mytilus edulis, having the potential to greatly reduce stocks in the benthic cultivation industry. As a consequence, baited crab pots are often deployed on and around cultivated benthic mussel beds to trap and remove crabs, in an attempt to reduce predatory pressure. Little is known about how C. maenas behaves around crab pots, but for many other crustacean fisheries, the trapping efficiency of pots is often low. Crabs may be attracted towards but not enter pots, instead feeding on cultivated mussels outside pots on the surrounding substratum. We tested whether the rate of loss of mussels attached to plates differed in areas next to baited pots compared with unbaited pots and to areas without any pots, at two sea loughs (60 km apart) in Northern Ireland. In Strangford Lough, more mussels were lost from plates next to baited pots than the other treatments. In Carlingford Lough, however, we found no difference in the number of mussels lost from plates in any treatment. This difference could be attributed to the different assemblages of mobile benthic predators at the two loughs. The presence of the starfish Asterias rubens, which was absent from experimental sites in Carlingford Lough, was thought to be responsible for increased predation rates near baited pots in Strangford. It is, therefore, important to consider local predator communities when deploying crab pots as a predator mitigation technique to ensure predation rates are in fact reduced and not enhanced. This study is of relevance not only to attempts to limit predation on commercial stocks of benthic cultivated mussels but also in situations where baited traps are deployed close to species vulnerable to mobile benthic predators.

Nursery areas and recruitment variation of Northeast Atlantic mackerel (Scomber scombrus)

Jansen T, Kristensen K, van der Kooij J, Post S, Campbell A, Utne KRong, Carrera P, Jacobsen JArge, Gudmundssdottir A, Roel BA, et al. Nursery areas and recruitment variation of Northeast Atlantic mackerel (Scomber scombrus). ICES Journal of Marine Science [Internet]. 2015 ;72(6):1779 - 1789. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsu186
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

There are currently no dedicated recruitment survey data available in support of the assessment of the abundance and distribution of Northeast Atlantic (NEA) mackerel (Scomber scombrus), one of the most widespread and commercially important fish stocks in the North Atlantic. This is despite the fact that an estimate of recruitment is an important requirement for the provision of advice to fishery managers. The work here addresses this by compiling catch rates of juvenile mackerel from bottom-trawl surveys conducted between October and March during 1998–2012 and applying a log Gaussian Cox (LGC) process geostatistical model incorporating spatio-temporal correlations. A statistically significant correlation between the modelled catch rates in adjacent quarters 4 and 1 (Q4 and Q1) demonstrates that bottom-trawl surveys in winter are an appropriate platform for sampling juvenile mackerel, and that the LCG model is successful in extracting a population abundance signal from the data. In this regard, the model performed appreciably better than a more commonly used raising algorithm based on survey swept-area estimates. Therefore, the LCG model was expanded to include data from the entire survey time-series, and a recruitment index was developed for use in the annual ICES stock assessment. We hypothesize that catchability is positively density-dependant and provides supporting evidence from acoustic observations. Various density-dependant transformations of the modelled catch rates were furthermore found to improve the correlation between the derived annual recruitment index and recruitment estimated by backcalculation of adult mackerel data. Square root transformation led to the strongest correlation, so this is recommended for further analysis of mackerel abundance. Finally, we provide maps of spatial distributions, showing that the most important nursery areas are around Ireland, north and west of Scotland, in the northern North Sea north of 59°N and, to some extent, also in the Bay of Biscay.

Maternal age effects on Atlantic cod recruitment and implications for future population trajectories

Shelton AOlaf, Hutchings JA, Waples RS, Keith DM, H. Akçakaya R, Dulvy NK. Maternal age effects on Atlantic cod recruitment and implications for future population trajectories. ICES Journal of Marine Science [Internet]. 2015 ;72(6):1769 - 1778. Available from: http://icesjms.oxfordjournals.org/lookup/doi/10.1093/icesjms/fsv058
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

Exploited fish populations frequently exhibit truncated age-structure. To address a basic question in fisheries science and conservation biology—how does age truncation affect population dynamics and productivity?—we explored the effect of age-structure on recruitment dynamics of ten stocks of Atlantic cod (Gadus morhua). Based on six alternative stock–recruitment relationships, we compared models that included and excluded maternal age-structure effects on recruitment. In all ten stocks, a recruitment model that included a maternal age-dependent effect was preferred over the standard Ricker model and in seven of the ten stocks, the preferred statistical model included a positive effect of either maternal age or mass on recruitment. Simulations comparing standard and maternal age dependent recruitment two decades into the future suggest that the inclusion of maternal age in recruitment models has little effect on projected biomasses. However, this similarity in biomass trajectory masked an increased sensitivity of populations with maternal age-dependent recruitment to stock age-structure. In particular, simulations with maternal age-dependent recruitment responded strongly to changes in fishing mortality on the oldest age classes, while simulations using standard recruitment models did not. Populations with maternal age-dependent recruitment can exhibit increased biomass catch even if fishing mortality on older individuals was reduced. Overall, simulations suggested that the influence of maternal age on population dynamics are more nuanced than suggested by previous research and indicate that careful consideration of the effects of age-structure on populations may lead to substantially different fisheries management reference points—particularly with respect to age-specific fishing mortality—than classical models. While these results suggest a link between maternal age and population productivity, future research requires the incorporation of biologically reasonable and empirically defensible mechanisms to clarify the effect of age on population dynamics.

Biodiversity baseline for large marine ecosystems: an example from the Barents Sea

Certain G, Planque B. Biodiversity baseline for large marine ecosystems: an example from the Barents Sea. ICES Journal of Marine Science [Internet]. 2015 . Available from: http://icesjms.oxfordjournals.org/cgi/doi/10.1093/icesjms/fsv040
Freely available?: 
No
Summary available?: 
No
Type: Journal Article

Biodiversity is an increasingly important issue for the management of marine ecosystems. However, the proliferation of biodiversity indices and difficulties associated with their interpretation have resulted in a lack of clearly defined framework for quantifying biodiversity and biodiversity changes in marine ecosystems for assessment purpose. Recent theoretical and numerical developments in biodiversity statistics have established clear algebraic relationships between most of the diversity measures commonly used, and have highlighted those that most directly relates to the concept of biological diversity, terming them “true” diversity measures. In this study, we implement the calculation of these “true” diversity measures at the scale of a large-marine ecosystem, the Barents Sea. We applied hierarchical partitioning of biodiversity to an extensive dataset encompassing 10 years of trawl-surveys for both pelagic and demersal fish community. We quantify biodiversity and biodiversity changes for these two communities across the whole continental shelf of the Barents Sea at various spatial and temporal scales, explicitly identifying areas where fish communities are stable and variable. The method is used to disentangle areas where community composition is subject to random fluctuations from areas where the fish community is drifting over time. We discuss how our results can serve as a spatio-temporal biodiversity baseline against which new biodiversity estimates, derived from sea surveys, can be evaluated.

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