Fisheries Management and Ecology | Year: 2013
Since the Common Fisheries Policy reform in 2002, there have been various proposals for designing effective input-management tools in the context of demersal multispecies and multimétier fisheries to augment quota management. The relationship between fishing mortality and effort exerted by the English beam trawl fleet is investigated for two stocks of North Sea demersal fish, plaice, Pleuronectes platessa L., and sole, Solea solea (L.). Catchability was adjusted by accounting for targeting by this gear, seasonal and area effects, and individual vessel variation, using results from a generalised linear mixed-effects model (GLMM) that included random effects (in this case, vessel). Descriptors were standardised in relation to distinct submétiers and their impact on both species. Fishing efficiency was calculated as the ratio between relative nominal landings per unit effort derived from the GLMM and survey indices from a standard survey vessel. Fishing efficiency for sole increased (+0.6% annually) and for plaice decreased (-6.2%), likely because of changes in targeting, fuel costs and regulations. © 2013 Crown.
Mirbahai L.,University of Birmingham |
Yin G.,BGI Shenzhen |
Bignell J.P.,CEFAS |
Li N.,BGI Shenzhen |
And 2 more authors.
Epigenetics | Year: 2011
The link between environment, alteration in DNA methylation and cancer has been well established in humans; yet, it is under-studied in unsequenced non-model organisms. The occurrence of liver tumors in the flatfish dab collected at certain UK sampling sites exceeds 20%, yet the causative agents and the molecular mechanisms of tumor formation are not known, especially regarding the balance between epigenetic and genetic factors. Methylated DNA Immunoprecipitation (MeDIP) combined with de novo high-throughput DNA sequencing were used to investigate DNA methylation changes in dab hepatocellular adenoma tumors for the first time in an unsequenced species. Novel custommade dab gene expression arrays were designed and used to determine the relationship between DNA methylation and gene expression. In addition, the confirmatory techniques of bisulfite sequencing PCR (BSP) and RT-PCR were applied. Genes involved in pathways related to cancer, including apoptosis, wnt/β-catenin signaling and genomic and nongenomic estrogen responses, were altered both in methylation and transcription. Global methylation was statistically significantly 1.8-fold reduced in hepatocellular adenoma and non-cancerous surrounding tissues compared with liver from non-cancer bearing dab. Based on the identified changes and chemical exposure data, our study supports the epigenetic model of cancer. We hypothesize that chronic exposure to a mixture of environmental contaminants contributes to a global hypomethylation followed by further epigenetic and genomic changes. The findings suggest a link between environment, epigenetics and cancer in fish tumors in the wild and show the utility of this methodology for studies in non-model organisms. © 2011 Landes Bioscience.
Tidd A.N.,CEFAS |
Hutton T.,CSIRO |
Kell L.T.,ICCAT Secretariat |
ICES Journal of Marine Science | Year: 2011
A profitable fishery attracts additional effort (vessels enter), eventually leading to overcapacity and less profit. Similarly, fishing vessels exit depending on their economic viability (or reduced expectations of future benefits) or encouraged by schemes such as decommissioning grants and/or when there is consolidation of fishing effort within a tradable rights-based quota system (e.g. individual transferable quotas). The strategic decision-making behaviour of fishers in entering or exiting the English North Sea beam trawl fishery is analysed using a discrete choice model by integrating data on vessel characteristics with available cost data, decommissioning grant information, and other factors that potentially influence anticipated benefits or future risks. It is then possible to predict whether operators choose to enter, stay, exit, or decommission. Important factors affecting investment include vessel age and size, future revenues, operating costs (e.g. fuel), stock status of the main target species, and the impact of management measures (e.g. total allowable catches) and total fleet size (a proxy for congestion). Based on the results, the predicted marginal effects of each factor are presented and the impact of each is discussed in the context of policies developed to align fleet capacity with fishing opportunities. ©  Crown copyright.
Szostek C.L.,Bangor University |
Murray L.G.,Bangor University |
Bell E.,CEFAS |
Rayner G.,Bangor University |
Kaiser M.J.,Bangor University
ICES Journal of Marine Science | Year: 2016
Scallop dredging is considered to be one of the most damaging forms of fishing to benthic habitats, although these effects vary among different habitats. The present study characterizes the biological communities that occur within the spatial limits of the English Channel king scallop dredge fishery in relation to key environmental drivers [mean seabed temperature; seabed temperature range; interannual temperature variation; bed shear stress (BSS); substrate characteristics; and depth] and across a gradient of scallop dredging intensity derived from vessel monitoring system data. Dredge fishing intensity was not correlated with species richness, species diversity, or species composition. However, increasing tidal BSS had a significant negative correlation with species richness and diversity. This outcome indicates that it is not possible to demonstrate that there is an effect of scallop fishing within the current spatial limits of the king scallop dredge fishery. This may be because historical dredge fishing could have already altered the benthic communities within the area of the scallop fishery to those that are resilient to scallop dredging, or that fishing disturbance has no impact over and above natural physical disturbance within the fishery. An analysis of biological and life history traits revealed that there was no relationship between recent fishing intensity, or BSS, and the functional composition of the communities present. However, even the lowest BSS values in the present study could be considered relatively high compared with areas outside the spatial boundaries of the fishery. Two distinct habitat groups were identified, based on the environmental drivers. These two groups were largely characterized by depth: deep (western) and shallow (eastern) sites. Species with traits that increase resilience to physical disturbance were abundant across all sample sites. Management concerning the environmental impacts of the fishery is discussed in terms of the spatial footprint of the fishery and predicted recovery time-scales for the associated benthic communities. © 2015 International Council for the Exploration of the Sea 2015. All rights reserved. For Permissions, please email: email@example.com.
Tidd A.N.,CEFAS |
Hutton T.,CSIRO |
Kell L.T.,ICCAT Secretariat |
Blanchard J.L.,University of Sheffield |
Blanchard J.L.,Imperial College London
Fisheries Research | Year: 2012
A discrete choice model is applied to determine how fishing effort is allocated spatially and temporally by the English and Welsh North Sea beam trawl fleet. Individual vessels can fish in five distinct areas, and the utility of fishing in an area depends on expected revenue measured as previous success (value per unit effort) and experience (past fishing effort allocation), as well as perceived costs (measured as distance to landing port weighted by fuel price). The model predicts fisher location choice, and the predictions are evaluated using iterative partial cross validation by fitting the model over a series of separate time-periods (nine separate time-periods). Results show the relative importance of the different drivers that change over time. They indicate that there are three main drivers throughout the study, past annual effort, past monthly effort in the year of fishing, and fuel price, largely reflecting the fact that previous practices where success was gained are learned (i.e. experience) and become habitual, and that seasonal variations also dominate behaviour in terms of the strong monthly trends and variable costs. In order to provide an indication of the model's predictive capabilities, a simulated closure of one of the study areas was undertaken (an area that mapped reasonably well with the North Sea cod 2001 partial closure of the North Sea for 10 weeks of that year). The predicted reallocation of effort was compared against realized/observed reallocation of effort, and there was good correlation at the trip level, with a maximum 10% misallocation of predicted effort for that year. © 2012.