Publication Abstract

Stock identity of elasmobranchs in the North-east Atlantic in relation to assessment and management

M.G.Pawson and J.R.Ellis

Whilst biological stocks delineate species' populations which may be considered as self-perpetuating units, the assessment of the abundance of a stock and its response to exploitation should encompass that part of a species' range in which the effects of exploitation in a particular fishery or fisheries are recognisable. Thus, fisheries are monitored and regulated in areas that may or may not coincide with biological stock boundaries. Such areas may be a management unit determined by the distribution of fisheries, but they should also include those parts of a particular species' population that have a high degree of biological integrity.

The natural variability and difficulty in measuring life-history and morphological characteristics at the population level suggest that these are not good indicators of stock separation for elasmobranchs. Information on population demography does, however, reveal the relationships between fisheries and resource, and indicates where sampling programmes for the collection of stock assessment data should take place. Tagging studies, in particular, can indicate a stock's main range and migrations, linked with a good description of the fisheries which share in its exploitation. The environmental parameters associated with the distribution of a species are also a useful guide to the likely boundaries of movement.

In this paper, we show how biological and fishery information has been used to describe the stock identity for nine case study species in the DELASS project, from which informed decisions have been taken on the areas to be used for stock assessments.

Reference:

M.G.Pawson and J.R.Ellis. 2002. Stock identity of elasmobranchs in the North-east Atlantic in relation to assessment and management. Journal of Northwest Atlantic Fishery Science 35, 173-193