Rachel Brown
PhD Student

Research

Overview

Title:  Untangling the effects of climate change and fishing on marine benthic communities.

Supervisor:  Bryce Beukers-Stewart

TAC:  Dave Raffaelli, Callum Roberts

Funding Source:  NERC Studentship

Description of Thesis:

Bottom fishing using towed nets and dredges has occurred for centuries and for as long as it has occurred there has been concern about it effects. It has been conducted on such a scale that it is often described as one of the greatest sources of anthropogenic disturbance to marine benthic communities. The gear used in bottom fisheries is designed to catch species that live within, on or in close association with the seabed. This gear is often indiscriminate and therefore incidental damage to non-target species that occur in this habitat is a common occurrence. Studies in recent years around the world have documented the long-term effects of bottom fishing and the results have been startling. However bottom fishing is just one of the anthropogenic impacts marine ecosystems have had to cope with over the last century. Eutrophication, pollution, ocean acidification and climate change all impact marine ecosystems as well. The problem is that these impacts rarely exist in isolation and synergies are often common. Alongside this our understanding of the long-term natural fluctuations and dynamics of marine communities is often incomplete, particularly because many communities have been altered in some way by anthropogenic activity prior to them being studied.

My thesis is investigating how the benthic communities around the Isle of Man in the Irish Sea respond to fluctuations in environmental conditions and fishing intensity over a long-term time-scale. There has been a commercial scallop fishery around the Isle of Man since 1937 when it developed following the collapse of fin-fish stocks. This fishery has seen many developments over the years and in the 1980s was at its largest, however at this time catch rates fell to a very low level. Since then several management measures have been introduced and the scallop grounds have seen some recovery. A closed season (June-October) was one of the management measures and alongside this bi-annual scallop surveys were conducted on all of the fishing grounds. These surveys not only monitored scallop populations but also quantified the bycatch. Several studies have been conducted around the Isle of Man looking at both the scallop populations and the bycatch from the fishery using the data from these surveys. However, now nearly two decades of data exists and alongside this environmental and fishing effort data has been collected over the same time period.  This has given me the unique opportunity to analyse the benthic communities over a long-term time period and take into account the different variables that may be affecting it.

I am approaching this analysis from several different angles, firstly I am studying the scallop populations to see if they can be used as bio-indicators for both anthropogenic and environmental change. I’m analysing the benthic communities on the different fishing grounds using the bycatch data collected in the bi-annual surveys mentioned above. There is also a large dataset from an area that has been closed to scallop dredging since 1989, which will be incorporated into the analysis as a benthic community unaffected by scallop dredging. This closed area has seen the scallop populations within it recover remarkably well since its closure and this is well documented in other published work. I am investigating how the rest of the benthic community has responded to the closure over the time-scale of this study, incorporating environmental variables into the analysis. Finally I am going to identify what they key drivers for change are within these benthic communities. This should then help feed into future management of the human activities around the Isle of Man.

Publications

Full publications list

Roberts, C.M., Brown, R.L., Davies, A., Molodstova, T., O’Leary, B.C., O’Rourke, M. (2008) Proposals for Protection of Areas on the High Seas in the OSPAR Region. University of York, 153 pp

Roberts, C.M, Brown, R. L., Thurstan, R., Hawkins, J.P. (2008) Selecting and implementing Highly Protected Marine Reserves in Wales. CCW Policy Research Report No. 08/17, Bangor 124 pp.