The need to understand the behaviour of fish reared for mariculture or restocking

Following severe stock collapses in many natural populations, efforts are now being invested in farming marine species, and in rehabilitating populations through controlled releases. While the development of cod farming is still relatively new, it may be wise to consider some of the problems other fish fanning industries have encountered. For example, fanned fish generally have a different genotype from that of local wild populations, and these artificially selected fish are typically bigger and more aggressive than wild fish. These differences can be problematic if fanned fish escape and begin breeding with local wild populations. An alternative approach to fanning is to rehabilitate local wild populations through restocking. To date, however, this approach has had mixed success. Fish behaviour develops during early life stages through a combination of innate characteristics and experience. Apparently, the capacity for behavioural flexibility later in life is affected by the early experiences of juvenile fish. Here, we review the literature concerning the role of population origin and juvenile experience on fish behaviour. We highlight our recent studies on Atlantic cod, which demonstrate that variability in the nursery habitat generates behaviourally flexible fish. We discuss these issues in the context of gadoid mariculture and restocking. We conclude that behavioural studies are an important part of applied research for developing an industry of fish fanning in gadoids, as well as for research concerning restocking and conservation of marine resources. (c) 2005 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.