Schooling properties of an obligate and a facultative fish species

Schooling fish species are conventionally subdivided into obligate and facultativ

Environmental assessment of the Peruvian industrial hake fishery with LCA

International audienceThe Peruvian hake (Merluccius gayi peruanus) stock has been in a delicate state in the last decades due to overexploitation combined with adverse climatic events. The stock is showing certain signs of recovery since 2012. This work analyses the environmental impacts of current fleet operations and its likely trend. The fleet was divided into coherent segments, per holding capacity and engine power. The validity of both segmentations, as well as the presence of an effect of economies of scale driving fuel use intensity (FUI), was tested. Life cycle assessment was used to calculate environmental impacts, per individual sampled vessel and per segment, complemented with indicators of energy efficiency and biotic resource depletion. The fleet is highly fuel-efficient (120 kg fuel per tonne fish) when compared with other reported values, despite a large overcapacity that increases the impact of the construction and maintenance phases. Significant inter-annual FUI variations were observed (80.0 kg t(-1) in 2008 to 210.3 kg t(-1) in 2006), but no clear trend. Neither significant differences in FUI among fleet segments nor a clear effect of economies of scale were found (but FUI analysis was based on a small sample of 32 values for nine vessels, two of which had data for a single year). Only the largest vessels, featuring 242 m(3) holding capacity and 850 hp engine power, were found to have lower FUI than any of the other vessels, but no statistical test could be applied to validate this difference. Differences in environmental impacts of individual vessels are mostly dominated by their relative FUI. Fuel use and, to a lower extent, maintenance are the main sources of environmental impacts. The most contributing impacts to ReCiPe single score are climate change, human toxicity and fossil depletion. The fishery's impacts on the biotic natural resource were orders of magnitude higher than many other global hake stocks, due to overexploitation. The environmental impacts of the national hake fleet are relatively low during the study period, despite an overcapacity of the fleet. With the perspective of expanding its operations and obtaining better yields on the eventuality that the stock fully recovers, these impacts should decrease. More research based on additional FUI data is necessary to effectively compare the performance of these vessels with larger ones (featuring \textgreater 180 m(3) and \textgreater 500 hp, of which nine existed in 2016) before possibly recommending their preferential use

Estimating environmental preferences of South African pelagic fish species using catch size- and remote sensing data

We have studied the relationship between the variations in density of South African anchovy (Engraulisi capensis), sardine (Sardinops sagax) and round herring (Etrumeus whiteheadi) from commercial catch records (1987-1997) and a suite of variables describing the environment. The indicator of density (local fish abundance) used was Catch-perset, obtained from the more than 130 000 catches made during the 11-year study period. The set of environmental parameters included: temporal (Year, Month, time of day or Hour), spatial (Latitude, Longitude and water Depth), lunar (Moon phase and Moon elevation), and thermal conditions of the environment (sea surface temperature together with indices of thermal frontal intensity and temporal change). Boat length was used to account for fishing gear effects. Previous investigations of this nature have tended to use simple bivariate correlation approaches, which suffer from the problem of covariance between the predictive variable and other environmental- or fisheries related variables not included in the analysis. We have, therefore, adopted a multivariate modelling approach, which identifies relationships between Catch-per-set and each environmental variable, accounting for covariation amongst predictors. Model building consisted of first constructing generalised additive models (GAM) as an exploratory tool to identify the shapes of the relationships, followed by parameterising these relationships using general linear models (GLM) to provide a robust predictive tool. Using this modelling approach, the suite of environmental variables explained 19.6% of the variation in Catch-per-set of anchovy, 33.9% of sardine, and 54.3% of round herring in the final GLM models. Temporal variables (Year, Month, Hour), accounted for the major part of the variability in Catch-per-set but variables derived from SST and the lunar cycle provide insight into the effects of environmental factors on fish behaviour. For instance, it appears that schooling behaviour of anchovy and round herring is affected by the level of solar and lunar illumination but that sardine is not affected. Model results further indicate that anchovies prefer water cooler than about 15 degreesC, demonstrates a weak tendency to concentrate near thermal fronts and avoids recently upwelled water. The sardine's preferences seem to be more or less the opposite to anchovy, i.e. it occur further from the coast and tends to concentrate in upwelled water which have been warmed to 14-19 degreesC; it shows no discernible tendency for aggregation near fronts. Round herring Catch-per-set strongly increases with water depth and reach a maximum near the shelf edge; it also demonstrates a notable tendency to concentrate near thermal fronts. SST seems to have no influence on round herring which is most often caught in the 15-18 degreesC range, typical of SSTs found in the vicinity of the oceanic front. (C) 2003 Elsevier Ltd. All rights reserved

Report on a GLOBEC-SPACC/IDYLE/ENVIFISH Workshop on Spatial Approaches to the Dynamics of Coastal Pelagic Resources and their Environment in Upwelling Areas.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra