A study was conducted on the ecology of larval gadoids in the Northern North Sea during April 1974 and late April/ early May 1975 with particular emphasis on the feeding ecology and separation of feeding niches of the five closely related species of larvae in the area. Food was shown to be a limiting resource for which the larvae competed, with larval mortality increasing with reduced food supply, and growth rates apparantly independent of food. Although shortage of food at first feeding was implicated in the very low densities of larval haddock, whiting and cod at the start of the 1975 cruise, it was apparent that food supply could become critical for survival at later stages in the larval phase. Hence no particular stage could be ascribed major importance in controlling subsequent recruitment, the process depending on the dynamic balance of larvae and food throughout the larval phase. Daily food intake was shown to be similar for four of the species, namely saithe, Norway pout, whiting and cod larvae, as was their gross feeding-efficiency. Haddock larvae, - on the other hand, appeared to consume a greater quantity of less nutritious food. Distributional, temporal and behavioural mechanisms were implicated in feeding niche separations such that there appeared to be little direct competition for food. However, recruitment data showed how saithe, whiting and cod tended to be negatively correlated with one another, and how haddock, Norway pout and to a lesser degree whiting showed positive cox-relations. Hence survival during the larval phase has been ascribed to the-pattern of -zooplankton productivity and its species composition.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:465800 |
| Date | January 1977 |
| Creators | Minton, Reginald C. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU428312 |
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