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Copyright of Aquatic Living Resources is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Aquatic Living Resources is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

According to the Ideal Free Distribution theory, individual fish are distributed where environmental conditions are optimal, and the occupied area may vary with population abundance. Thus, observed distributions are a combination of habitat suitability and density-dependent effects. Data from an annual bottom trawl survey taking place in autumn were used to assess associations between the distributions of eight demersal fish species, separately for juveniles and adults, and habitat characteristics (depth, temperature and salinity) in the Bay of Biscay and Celtic Sea. Cumulative distribution functions were used to describe the general frequency distributions of environmental variables and their relationships with fish density. During the period 1992–2006, observed bottom temperatures fluctuated with no time trend (ΔT = 8°C in the first 80 m) and population abundances varied significantly. Juvenile hake, poor cod, blue whiting, adult red gurnard, adult megrim, and lesser-spotted dogfish were found to be significantly associated with specific depth ranges. Associations with bottom temperature and salinity were weaker. For some species, preferred environmental conditions changed over time, independently of variations in environmental conditions. In general, most species seemed to be able to cope with the experienced range of conditions. Habitat associations were not influenced by abundance variations. Fluctuating abundances had an impact on spatial occupation only for red gurnard adults, lesser-spotted dogfish and blue whiting juveniles, independent of absolute densities. [ABSTRACT FROM AUTHOR]

Trenkel, V. M., Mazauric, V., and Berger, L. 2008. The new fisheries multibeam echosounder ME70: description and expected contribution to fisheries research. – ICES Journal of Marine Science, 65: 645–655. Recently, Simrad in collaboration with Ifremer developed a calibrated, multibeam, vertical echosounder (ME70) for fisheries research. We describe its capabilities and technical limitations. The ME70 has up to 45 beams with distinct frequencies in the range 70–120 kHz, spanning at most 150°. All beams are stabilized in vessel roll and pitch. It has reduced side-lobe levels, up to −70 dB (two-way) instead of the −25 dB (one-way) of conventional systems. We outline research areas for which the ME70 might provide new types of information and hence lead to novel insights. We illustrate the potential contributions with datasets collected in the English Channel and on the continental-shelf break of the Bay of Biscay. Finally, future research and developments using the new system are outlined. [ABSTRACT FROM PUBLISHER]

Abstract: The behaviour of eight large benthopelagic fish taxa was analysed using video records collected with an ROV on the mid-slope of the Bay of Biscay. The studied species were roundnose grenadier (Coryphaenoides rupestris), orange roughy (Hoplostethus atlanticus), deep-sea scorpionfish (Trachyscorpia cristulata echinata), and black scabbardfish (Aphanopus carbo), as well as individuals belonging to the families Alepocephalidae, Chimaeridae, and Scyliorhinidae, and to the order Squaliformes. Some of the observed fish were grouped at the family taxonomical level due to visual identification to species being unreliable. Assumed natural (undisturbed) behaviour was categorised in terms of (i) body position with respect to the bottom sea floor, (ii) locomotion and (iii) activity type. Reaction (disturbed) behaviour to the approaching ROV was categorised in terms of reaction type and distance. Environmental conditions (depth, temperature, current speed and direction) and observation conditions (ROV speed and altitude) were recorded simultaneously with fish observations in order to explain the variability in the observed reaction behaviour. A multivariate analysis identified three groups corresponding to a behaviour pattern of a sit and wait strategist (one species), an active bottom hunter (three taxa), and a group of species displaying little activity in their bottom habitat (three taxa). At species level the environmental and observation conditions had some explanatory power for individual behaviour variability. It is hypothesised that the varied behaviour of mid-slope benthopelagic fish contributes to maintain a high species diversity of large predators in an energy poor environment. [Copyright &y& Elsevier]