Commercial fishing for Pecten maximus and Aequipecten opercularis has taken place in Shetland since the late 1960’s and early 1970’s, respectively, with fluctuations in landings of both species during this time. Recognition of the importance that shellfish fishing contributes towards maintaining a diverse economy in a rural area, coupled with concerns in the 1990’s about the potential for overfishing, prompted by reductions in the abundance of some shellfish species, the Shetland Shellfish Management Organisation Ltd. was formed, with a remit to implement local management of shellfish stocks, where necessary. The collection of biological data was started and the completion of log books begun in 1999 and 2000, respectively, to provide data to assess the species, with a view to their sustainable management. Von Bertalanffy growth parameters were determined for contemporary samples on both species and on historical samples of P. maximus. The asymptotic shell length, as a measure of growth, was examined in relation to the environmental variables of sediment composition and depth. Growth studies were carried out on juveniles to measure sub-annual growth. The gonadal condition through time in the adult stocks was assessed, changes in gonad condition were related to spawning activity by collection of spat on artificial collectors. Seasonal and spatial differences in yield of adductor muscle and gonad from experimentally derived, and commercial yield data, was analysed. The assessment of the fishery utilised fisher knowledge on the distribution of stocks. Catch Per Unit Effort and mortality rates data were calculated. The overall Spawning Stock Biomass was estimated for P. maximus using the swept area method. Long-term data from processing factories were incorporated into the fisheries assessment. The assessment indicates poor catches of A. opercularis for many years, and a recovery in abundance of P. maximus on some fishing grounds since the low catches experienced in 2000.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:522241 |
| Date | January 2010 |
| Creators | Campbell, Allan |
| Publisher | Open University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://pure.uhi.ac.uk/portal/en/studentthesis/the-fisheries-biology-of-two-scallop-species-pecten-maximus-l-and-aequipecten-opercularis-l-in-the-waters-around-shetland-scotland(05aefd3d-c197-4288-abe6-f3e77b9fb609).html |
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