The effect of dredge capture on the escape response ž / of the great scallop , Pecten maximus L . : implications for the survival of undersized discards

The effect of dredge capture on the escape response ž / of the great scallop, Pecten maximus L. : implications for the survival of undersized discards Abstract The effect of simulated dredge capture on the swimming escape response of the great scallop, Pecten maximus, was assessed in order to determine the potential for mortality in undersized discards. Three experiments were carried out: firstly, to determine how the effect of simulated dredging on the escape response varied with season and scallop size; secondly, to assess the time taken for scallops to recover following simulated dredging; and thirdly, to determine the interactive effects of dredging, exposure to air and recovery time. In all experiments, simulated dredging caused a significant increase in the response time of scallops and a significant decrease in the number of valve adductions performed. The negative effects of dredging occurred Ž. irrespective of season spring versus autumn and scallop size. Exposure to air also had a negative effect on the escape response, which was evident in both dredged and nondredged scallops. Determination of the period taken to recover showed that although some recovery was evident after 1 h, the negative effects of simulated dredge capture were still apparent after a period of 24 h. These results suggest that there is a potential for high levels of mortality in undersized discarded scallops, and scallops which encounter dredges but are not captured. q 2001 Elsevier Science B.V. All rights reserved.