9781888569605-ch22

Benthic Habitats and the Effects of Fishing

Symposium Abstract: Fast-Track Methods for Assessing Trawl Impacts

R. A. Coggan, C. J. Smith, R. J. A. Atkinson, K. N. Papadopoulou, T. D. I. Stevenson, P. G. Moore, and I. D. Tuck

doi: https://doi.org/10.47886/9781888569605.ch22

Traditional methods for assessing the impact of towed demersal fishing gear are notoriously slow, taking years to report and imposing undesirable delays in the provision of scientific advice on which fisheries and environmental managers can act. There is a need to develop rapid methods for assessing trawl impacts. We evaluate and compare a suite of rapid methodologies covering a range of readily accessible technologies including:

(1) Acoustic methods: sidescan sonar and bottom discriminating sonar (RoxAnn);

(2) Visual methods: towed video sledge and ROV;

(3) Faunal sampling (epibenthic megafauna): tissue damage, community analysis, population density, functional group composition; and

(4) Sedimentology: granulometry, geotechnical properties and sediment profile imagery.

These methods were applied to otter trawl fisheries in the Clyde Sea, Scotland and the Aegean Sea, Mediterranean, at sites representing a range of trawl impacts. Novel methods of analysis were developed for quantitative interpretation of sidescan and video records. The scientific effectiveness, cost effectiveness and operational constraints of the various methodologies are reviewed. We recommend suitable approaches to the rapid assessment of trawl impacts taking into consideration the variety of resources (such as time, equipment and budget) which may be available. Assessments should employ complementary methods that operate on different scales of resolution (eg. sidescan sonar with either faunal sampling or ROV). Site-specific factors, such as topography and substratum type, will influence choice of methods and survey design. These rapid methodologies can provide results in a matter of days or weeks rather than the months or years associated with traditional assessment methods.