The fisheries biology of two scallop species, Pecten maximus (l.) and Aequipecten opercularis (l.), in the waters around Shetland, Scotland.

Commercial fishing for Pecten maximus and Aequipecten opercularis<br/>has taken place in Shetland since the late 1960’s and early 1970’s,<br/>respectively, with fluctuations in landings of both species during this time.<br/>Recognition of the importance that shellfish fishing contributes towards<br/>maintaining a diverse economy in a rural area, coupled with concerns in the<br/>1990’s about the potential for overfishing, prompted by reductions in the<br/>abundance of some shellfish species, the Shetland Shellfish Management<br/>Organisation Ltd. was formed, with a remit to implement local management of<br/>shellfish stocks, where necessary. The collection of biological data was started<br/>and the completion of log books begun in 1999 and 2000, respectively, to<br/>provide data to assess the species, with a view to their sustainable<br/>management.<br/>Von Bertalanffy growth parameters were determined for contemporary<br/>samples on both species and on historical samples of P. maximus. The<br/>asymptotic shell length, as a measure of growth, was examined in relation to<br/>the environmental variables of sediment composition and depth. Growth<br/>studies were carried out on juveniles to measure sub-annual growth.<br/>The gonadal condition through time in the adult stocks was assessed,<br/>changes in gonad condition were related to spawning activity by collection of<br/>spat on artificial collectors. Seasonal and spatial differences in yield of<br/>adductor muscle and gonad from experimentally derived, and commercial<br/>yield data, was analysed.<br/>The assessment of the fishery utilised fisher knowledge on the<br/>distribution of stocks. Catch Per Unit Effort and mortality rates data were<br/>calculated. The overall Spawning Stock Biomass was estimated for P.<br/>maximus using the swept area method. Long-term data from processing<br/>factories were incorporated into the fisheries assessment. The assessment<br/>indicates poor catches of A. opercularis for many years, and a recovery in<br/>abundance of P. maximus on some fishing grounds since the low catches<br/>experienced in 2000.

Name dc:type.qualificationname

Doctor of Philosophy (awarded by OU/Aberdeen)

Level dc:type.qualificationlevel

Doctoral Thesis

Year dc:date.issued

2010

Author dc:creator

• Campbell, Allen

Language dc:language

eng

Identifier

oai:pure.atira.dk:studenttheses/05aefd3d-c197-4288-abe6-f3e77b9fb609

OAI identifier oai:identifier

oai:pure.atira.dk:studenttheses/05aefd3d-c197-4288-abe6-f3e77b9fb609