Pollack (Pollachius pollachius) stock size development and potential influence on cod (Gadus morhua) mariculture in a west Norwegian fjord
1995; Elsevier BV; Volume: 24; Issue: 3 Linguagem: Inglês
10.1016/0165-7836(95)00369-l
ISSN1872-6763
Autores Tópico(s)Marine Bivalve and Aquaculture Studies
ResumoThis study examines density-dependent mortality of pollack, a major cod predator, and cod, before and after juvenile cod were released on a large scale in Masfjorden, western Norway. The development in stock size, mortality by age group and diet are emphasised, and results for pollack and cod are compared. Population parameters for pollack are estimated using a combination of the catch per unit effort (CPUE) method and a general cohort analysis technique. The estimates for cod originate from a combination of the CPUE method and tag-release-recapture experiments and have been published earlier. The diet studies are based on pollack and cod subdivided into predator size groups for four seasons at a period before large-scale juvenile cod releases. During this period, but also after releases, the mortality patterns, stomach analysis and the progression in prey (1-group) and predator (2 + -group) abundance demonstrate cannibalism as well as that pollack and cod were feeding on each other's juveniles in Masfjorden. Density-dependent predation mortality and growth seem to be an important regulatory mechanism for pollack and cod stocks in Masfjorden. This may explain the unsuccessful cod mariculture in this fjord.
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