Assessing consistency of fish survey data : uncertainties in the estimation of mackerel icefish (Champsocephalus gunnari) abundance at South Georgia

Acknowledgments The authors wish to thank the crews, fishermen and scientists who conducted the various surveys from which data were obtained, and Mark Belchier and Simeon Hill for their contributions. This work was supported by the Government of South Georgia and South Sandwich Islands. Additional logistical support provided by The South Atlantic Environmental Research Institute with thanks to Paul Brickle. Thanks to Stephen Smith of Fisheries and Oceans Canada (DFO) for help in constructing bootstrap confidence limits. Paul Fernandes receives funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland), and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. We also wish to thank two anonymous referees for their helpful suggestions on earlier versions of this manuscript.Peer reviewedPostprin

Warming temperatures and smaller body sizes : synchronous changes in growth of North Sea fishes

Funded by Marine Scotland SciencePeer reviewedPostprin

Bayesian fitting of probabilistic maturation reaction norms to population-level data

Probabilistic maturation reaction norms (PMRNs) are an important tool for studying fisheries-induced evolution and environmental effects on life history. To date there has been no way to fit a PMRN to population-level fisheries data; instead individual-level data must be used. This limits the stocks and time periods that can be studied.We introduce a Bayesian method for fitting PMRNs to population-level data. The method is verified against both an existing result and simulated data, and applied to historical Barents Sea cod data which combines observations of population-level variation in age, size and maturity status from Russia and Norway.The method shows a clear and rapid trend towards greater probability of maturation at smaller lengths in the Barents Sea cod.The new model fitting algorithm allows us to study historic changes in life history despite the lack of individual-level data seen in much long term data. Access to more data will aid the study of evolutionary hypotheses in a wide range of organisms

Interannual variations in the liver condition index of cod as an indicator of temperature and feeding conditions in the Barents Sea

Background: Northeast Arctic cod, inhabiting the edge of the species area, experience variable environmental conditions and feeding resources, one of the main of them is capelin. Lipids are an important biochemical link between capelin and cod. Lipids constitute approximately 10-15% of the total wet weight of capelin at the peak of their seasonal cycle in lipid accumulation (Jangaard 1974). In contrast, approximately 1% of the wet weight of the muscle tissue of cod is composed of lipids (Lie et al. 1988). The liver is the primary site of stored lipid reserves in cod. These reserves are utilized during periods of food limitation and the annual cycle of gonad maturation. Starved cod can replenish liver reserves rapidly in response to increased food (Karlsen et al. 1995). Lliver weight is likely to be a dynamic index of the physiological condition of cod

The impact of electronic monitoring on fleet wide discarding of small cod in Scottish demersal fisheries

Acknowledgments The authors of this paper would like to acknowledge the fishers, fisheries inspectors, and video reviewers who participated in or supported the Scottish cod catch quota management scheme. Additionally, we thank two anonymous reviewers for their encouraging and insightful comments and suggestions.Peer reviewedPublisher PD

Abundance and mortality of Northeast Arctic cod and haddock during their first years of life

For Northeast Arctic cod and haddock in the Barents Sea, long time series of year-class abundance are available at several stages before they recruit to the fishery, i. e. before they reach age 3. Several studies have already been made of the influence of various factors on the abundance and survival of these stocks during the first three years of life, in particular for cod. However, revision of existing data series as well as availability of longer data series makes a new analysis worthwhile. The analysis includes VPA estimates of recruitment, as well as estimates of total egg production and survey estimates from pelagic and bottom trawl surveys. The mortality between various life stages is found to vary considerably between cohorts for both stocks. Although and the mortality is highest during the first months of life, the year-class strength can also be affected considerably by processes taking place between the 0-group stage (ca. 6 months) and age 3. The mortality in this period of life seems to be strongly density –dependent for both stocks. The estimates of 0- and 1-group abundance of cod and haddock from different sources (0-group pelagic trawl and acoustic, 1-group XSA and trawl) give numbers which are compatible with each other. The ratio between haddock and cod recruitment at age 3 is higher in the period after 1980 than before 1980, this may be due to higher temperature in the latter period. High haddock recruitment never occurs when cod recruitment is low

Shifts in spawning phenology of cod linked to rising sea temperatures

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FIS workshop on Global synthesis of climate impacts on fish distribution and growth and implications for Scottish fisheries : FIS028

All workshop attendees and remote participants (identified in Table 1) are thanked for their contributions to presentations, discussion and this report. A. Audzijonyte, R. Allman, B. Bogstad, C. Champion, T. Essington, M. Haltuch, A. Haynie, T. Helser, E. Hjörleifsson, J. Morrongiello, M. Peck, G. Pecl, J. Pinnegar, M. Pinsky, C. Stawitz, B. Townhill, J. Thorson, and P.D. van Denderen contributed text to this report. George R. West is thanked for his participation in the public event. Jens Rasmussen assisted in the development of recommendations for future research. The assistance of Mindfully Wired Communications (Harriet Yates and Ginny Russell) is gratefully acknowledged.Publisher PD

Disentangling the effects of fishing and temperature to explain increasing fish species richness in the North Sea

Funding This studentship has been funded under the NERC Scottish Universities Partnership for Environmental Research (SUPER) Doctoral Training Partnership (DTP) (Grant reference number NE/S007342/1 and website https://superdtp.st-andrews.ac.uk/). Additional funding has been provided by Marine Scotland and the University of Aberdeen.Peer reviewedPublisher PD