Lookup NU author(s): Professor Nick Polunin,
Dr Benjamin Wigham
Point survey techniques such as baited traps and trammel nets may be better than trawling for detecting small-scale differences in mobile macroconsumer (here fish and crustacean) diversity. Yet very few studies have compared the relative merits of trawl and point count data in monitoring, environmental impact and research work. This project off the Northumberland coast set out to compare advantages and disadvantages of trawl, trammel and trap sampling techniques for detecting spatial and habitat-related variations in fish and crustacean species richness. Sampling over a range of depths and on two broad habitat types (soft and intermediate [partly rocky] seabed) showed species richness and abundance varying considerably among sites and gears. Trawling detected the largest number of species, but failed to catch, or under-represented, a number of commercially important demersal species present in trammel net samples. Gear type appeared to be the main variable driving differences among samples overall, although individual gears detected significant effects of other variables. All three gears detected significant effects of depth, but only traps detected significant effects of habitat on sample assemblages. The inherent variability of data and the difficulty of controlling for many factors limit the conclusions which can be reached using such marine ecological data, however, a combination of trawling and point sampling is likely to provide more comprehensive data on diversity and abundance of mobile macroconsumer species.
Author(s): Polunin NVC, Peacock S, Hardy MH, Royle J, Wigham BD
Publication type: Report
Source Publication Date: March 2012
Institution: Marine Management Organisation
Place Published: Newcastle University