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Impacts on marine survival of Atlantic salmon Salmo salar include sea lice Lepeophtheirus salmonis infestation from coastal aquaculture, and ocean climate forcing. These effects may interact because infestation compromises smolt growth and body condition, and thus response to environmental conditions. We hypothesized that migrating smolts exposed to lice from salmon farms would show (i) reduced one sea-winter (1SW) returns to natal rivers and (ii) a shift in relationships between ocean climate and returns. Annual counts of 1SW fish were studied from ten rivers in Ireland, including five "control" systems without salmon aquaculture. Most counts showed a downward trend, consistent with declines in Atlantic salmon populations. Rivers with aquaculture showed lesser returns (mean 33%, range 19–46%) in years following high lice levels on nearby salmon farms. The level of likely lice pressure also modified how annual 1SW returns varied with ocean conditions. Returns to control rivers showed a weak negative relationship with the Atlantic Multi-decadal Oscillation (AMO) in the late summer (September) of the out-migrating year. This negative AMO effect became much stronger for fish migrating in low lice years but was not evident for high lice years. Smolts experiencing mild-to-moderate lice infestation may show greater sensitivity to ocean warming. [ABSTRACT FROM AUTHOR]

Pretty good yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large percentage of the maximum sustainable yield (MSY). We investigated 19 European fish stocks to test the hypothesis that the 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An FMSY range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at least 95% of MSY in long-term simulations. Further, a precautionary reference point for each stock (FP.05) was defined as the F resulting in a 5% probability of the spawning-stock biomass falling below an agreed biomass limit below which recruitment is impaired (Blim) in long-term simulations. For the majority of the stocks analysed, the upper bound of the FMSY range exceeded the estimated FP.05. However, larger fish species had higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to have FMSY ranges impairing recruitment. Our study shows that fishing at FMSY generally is precautionary with respect to impairing recruitment for highly exploited teleost species in northern European waters, whereas the upper part of the range providing 95% of MSY is not necessarily precautionary for small- and medium-sized teleosts. [ABSTRACT FROM AUTHOR]

The European Union Marine Strategy Framework Directive (MSFD) uses indicators to track ecosystem state in relation to Good Environmental Status (GES). These indicators were initially expected to be "operational", i.e. to have well-understood relationships between state and specified anthropogenic pressure(s), and to have defined targets. Recent discussion on MSFD implementation has highlighted an additional class of "surveillance" indicators. Surveillance indicators monitor key aspects of the ecosystem for which there is: first, insufficient evidence to define targets and support formal state assessment; and/or second, where links to anthropogenic pressures are either weak or not sufficiently well understood to underpin specific management advice. Surveillance indicators are not only expected to directly track state in relation to GES, but also to provide complementary information (including warning signals) that presents a broader and more holistic picture of state, and inform and support science, policy, and management. In this study, we (i) present a framework for including surveillance indicators into the Activity-Pressure-State-Response process, (ii) consider a range of possible indicators that could perform this surveillance role, and (iii) suggest criteria for assessing the performance of candidate surveillance indicators, which might guide selection of the most effective indicators to perform this function. [ABSTRACT FROM AUTHOR]

Pelagic fish are key elements in marine foodwebs and thus comprise an important part of overall ecosystem health. We develop a suite of ecological indicators that track pelagic fish community state and evaluate state of specific objectives against Good Environmental Status (GES) criteria. Indicator time-series are calculated for the EU Marine Strategy Framework Directive “Celtic Seas” (CS) and “Greater North Sea” subregions. Precautionary reference points are proposed for each indicator and a simple decision process is then used to aggregate indicators into a GES assessment for each subregion. The pelagic fish communities of both subregions currently appear to be close to GES, but each remains vulnerable. In the CS subregion, fishing mortality is close to the precautionary reference point, although the unknown dynamics of sandeel, sprat, and sardine in the subregion may reduce the robustness of this evaluation. In the North Sea, sandeel stocks have been in poor state until very recently. Pelagic fish community biomass is slightly below the precautionary reference point in both subregions. [ABSTRACT FROM PUBLISHER]

Shephard, S., Minto, C., Zölck, M., Jennings, S., Brophy, D., and Reid, D. 2014. Scavenging on trawled seabeds can modify trophic size structure of bottom-dwelling fish. – ICES Journal of Marine Science, 71: 398–405.Disturbance by towed bottom-fishing gears often kills larger sensitive benthos, leading to changes in the abundance, size, and species composition of benthic communities. Short-term availability of trawl-damaged prey, and longer-term shifts in benthic prey community composition, both have the potential to affect feeding opportunities and realized dietary preferences of bottom-feeding (benthivorous) fish. To investigate these effects of bottom-fishing activity (by otter trawls, beam trawls, and dredges) on the feeding of benthivorous fish, we compared the trophic level at body size and diets of four species in areas of the Celtic Sea subject to low, intermediate, and high fishing activity. Trophic level was estimated using nitrogen stable isotope analysis, and fishing activity was quantified with vessel monitoring system (VMS) data. For whiting (Merlangius merlangus) of all sizes, trophic level was slightly lower in areas of higher fishing activity. After accounting for the results of the diet analysis, we concluded that this reflected increased scavenging of benthic invertebrates in more intensively fished areas. For megrim (Lepidorhombus whiffiagonis), the rate of increase in trophic level with size was lower with increasing fishing activity, implying that megrim may also substitute fish with lower-trophic invertebrates that can be scavenged in more intensively fished areas. For plaice (Pleuronectes platessa) and lemon sole (Microstomus kitt), no significant effects of fishing activity on trophic level were detected. We conclude that differences in the intensity of fishing activity with towed bottom gears had small but variable effects of the trophic size structure of the four species, and that this primarily reflected scavenging rather than diet changes following longer-term shifts in composition of the prey community. [ABSTRACT FROM PUBLISHER]

Shephard, S., Fung, T., Houle, J. E., Farnsworth, K. D., Reid, D. G., and Rossberg, A. G. 2012. Size-selective fishing drives species composition in the Celtic Sea. – ICES Journal of Marine Science, 69: 223–234.Fishing alters community size structure by selectively removing larger individual fish and by changing the relative abundance of different-sized species. To assess the relative importance of individual- and species-level effects, two indices of fish community structure were compared, the relative abundance of large fish individuals (large fish indicator, LFI) and the relative abundance of large fish species (large species indicator, LSI). The two indices were strongly correlated for empirical data from the Celtic Sea and for data from simulated model communities, suggesting that much of the variability in the LFI is caused by shifts in the relative abundance of species (LSI). This correlation is explained by the observation that most of the biomass of a given species is spread over few length classes, a range spanning the factor 2 of individual length, such that most species contributed predominantly to either the small or the large component of the LFI. The results suggest that the effects of size-selective fishing in the Celtic Sea are mediated mainly through changes in community composition. [ABSTRACT FROM PUBLISHER]

Shephard, S., Gerritsen, H. D., Kaiser, M. J., Truszkowska, H. S., and Reid, D. G. 2011. Fishing and environment drive spatial heterogeneity in Celtic Sea fish community size structure. – ICES Journal of Marine Science, 68: 2106–2113.The Large Fish Indicator (LFI) is a univariate size-based indicator of fish community state that has been selected to support the OSPAR fish community Ecological Quality Objective (EcoQO). To operate this EcoQO, a survey-based LFI for each OSPAR region needs to be developed. However, fish communities in these regions are spatially heterogeneous, and there is evidence of within-region spatial variation in the LFI that could confound an overall indicator series. For Celtic Sea trawl-survey sites, spline correlograms indicate positive spatial autocorrelation at a similar range (∼40 km) for the LFI and for fishing effort (h year−1) from vessel monitoring systems. Statistical models reveal a strong negative effect on annual LFI by site of fishing effort within a radius of 40 km. There was a weak effect of fishing within 20 km and no effect at 10 km. LFI also varied significantly with substratum and with local fish community composition identified by a resemblance matrix derived from the survey data. Finally, there was a weak effect of survey year on LFI. Spatial stratification of LFI calculations may be necessary when developing size-based indicators for OSPAR or Marine Strategy Framework Directive regions. [ABSTRACT FROM PUBLISHER]

Shephard, S., Reid, D. G., and Greenstreet, S. P. R. 2011. Interpreting the large fish indicator for the Celtic Sea. – ICES Journal of Marine Science, 68: 1963–1972.The large fish indicator (LFI) was developed in the North Sea as a size-based indicator of fish community state. It is now established as OSPAR's fish community Ecological Quality Objective (EcoQO) metric and will be applied across all OSPAR regions. To produce a protocol for use when developing regional LFIs, the North Sea experience is interpreted using data from the Celtic Sea. Differences in fish community species composition and size distribution were reflected in a different species complex and large fish threshold (50 cm) for the Celtic Sea LFI. However, a lag of 12–14 years in the relationship between assemblage-averaged fishing mortality Fcom,y and the LFI suggested similar underlying ecological mechanisms to the North Sea. The indicator responded to changes in small fish biomass that follow fishing-induced changes in the level of predation by large demersal piscivores. The Celtic Sea LFI showed maximum observed values >0.40 before 1990, and 0.40 is here proposed as an EcoQO. Development of regional LFIs demands a flexible process rather than a strictly prescriptive protocol. [ABSTRACT FROM PUBLISHER]

S. Shephard, P. Connolly, N.-R. Hareide, and E. Rogan. 2007. Establishing stakeholder connections for management of the Irish orange roughy fishery. – ICES Journal of Marine Science, 64: 841–845.In 2000, an Irish fishery for orange roughy commenced in ICES Subarea VII. Landings peaked at >5000 t in 2002, but the fishery was largely closed from January 2005 because of concern about unsustainable fishing and the negative effects on deepwater sharks and coral. A multidimensional project was initiated in 2003 to investigate the fishery system and to develop a management plan. The project emphasized the establishment of productive relationships with stakeholders, particularly fishers. We describe and evaluate the process by which such linkages were developed successfully. Informal discussion with fishers produced experiential knowledge that described fishery development and fishing strategies, and informed subsequent scientific data collection. Strengthening relationships permitted access to commercial fishing trips and cooperation in research. An atmosphere developed in which management options could be debated in both wheelhouse and boardroom. Eventually, a formal research/stock assessment survey took place in which fishers, agencies, and deepwater coral ecologists cooperated. [ABSTRACT FROM PUBLISHER]