Prior to 2010, megrim in the northern North Sea was not considered in the annual stock assessment for the species on the Northern Shelf. The underlying aim of this study was to fill some of the current knowledge gaps in megrim biology and ecology in the northern North Sea, providing improved scientific information that is intended to assist in the development of an informed assessment of the stock in future years. Changes in the distribution and relative abundance of common megrim Lepidorhombus whiffiagonis in the North Sea were investigated by comparing three data sources: fishers' knowledge collected through a structured questionnaire; a vessel's haul-by-haul catch data from the personal diaries of a single skipper over a 10-year time-series, and catch rates from fishery-independent surveys (IBTS Q1 and Q3). A number of life history characteristics of the common megrim Lepidorhombus whiffiagonis (Walbaum) were compared between the northern North Sea and Rockall, the latitudinal extremes of the species' distribution on the Northern Shelf. An estimation of the potential and relative fecundity of L. whiffiagonis was also presented for the first time. Furthermore, genetic analyses of adult megrims captured on the Northern Shelf were used to determine whether there was evidence of separate populations on the northern Shelf, the geographic distributions of any separate populations and whether the evidence from this genetic study supports the management units implemented in 2011. Finally, temporal variation in megrim discarding in the mixed demersal fishery in the northern North Sea prior to, and following recent quota increases was investigated. Logistic regression models were applied to investigate the effects of a range of explanatory factors on the probability of individual fish being discarded.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606450 |
| Date | January 2014 |
| Creators | Macdonald, Paul |
| Contributors | Angus, Chevonne |
| Publisher | University of the Highlands and Islands |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://pure.uhi.ac.uk/portal/en/studentthesis/increasing-understanding-of-a-data-poor-species-to-improve-resource-management(7a040168-feab-450c-a27a-09d1bcb1d84e).html |
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