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Fish stock fluctuations are affected by two potentially confounding forces: the removal of individuals by fisheries and climatic variations affecting the productivity of fish populations. Disentangling the relative importance of these forces has thus been a question of primary importance for fisheries management and conservation. Through the analysis of long-term time-series for 27 fish stocks from the Northeast Atlantic, the present study shows that the sign and intensity of the effect of temperature on biomass are dependent on the geographical location: the stocks located at the southernmost and northernmost latitudes of our study displayed stronger associations with temperature than the stocks located in the middle range of latitudes. As a consequence, the investigation of the combined effects of exploitation and the environment revealed that the stocks at the northern/southern boundaries of the spatial extent of the species were more prone to combined effects. The interplay between geographic location, climate and exploitation thus plays a significant role in fish stock productivity, which is generally ignored during assessment, thus affecting management procedures. [ABSTRACT FROM PUBLISHER]

This paper provides an exploratory analysis aiming to seek whether the colour of environmental noise theory could help in understanding the intriguing reproductive strategy of Atlantic bluefin tuna (BFT). A frequency-based approach based on spectral exponents, f β with β < 0, is chosen and applied on 10 biogeographical provinces covering the North Atlantic. The major BFT spawning area, i.e. the Mediterranean Sea, was the only one to display a pink power spectrum, whereas open ocean regions displayed more reddened fluctuations, i.e. greater variance at low frequencies. Environmental noise in the Mediterranean could, thus, offer more favourable characteristics on the long-term than the open ocean. The implications of these findings are discussed in regards to medium and long (possibly evolutionary) time scales. [ABSTRACT FROM AUTHOR]

Abstract: Catch data of large pelagic fish such as tuna, swordfish and billfish are highly variable ranging from short to long term. Based on fisheries data, these time series are noisy and reflect mixed information on exploitation (targeting, strategy, fishing power), population dynamics (recruitment, growth, mortality, migration, etc.), and environmental forcing (local conditions or dominant climate patterns). In this work, we investigated patterns of variation of large pelagic fish (i.e. yellowfin tuna, bigeye tuna, swordfish and blue marlin) in Japanese longliners catch data from 1960 to 2004. We performed wavelet analyses on the yearly time series of each fish species in each biogeographic province of the tropical Indian and Atlantic Oceans. In addition, we carried out cross-wavelet analyses between these biological time series and a large-scale climatic index, i.e. the Southern Oscillation Index (SOI). Results showed that the biogeographic province was the most important factor structuring the patterns of variability of Japanese catch time series. Relationships between the SOI and the fish catches in the Indian and Atlantic Oceans also pointed out the role of climatic variability for structuring patterns of variation of catch time series. This work finally confirmed that Japanese longline CPUE data poorly reflect the underlying population dynamics of tunas. [Copyright &y& Elsevier]