The implications of spatial and temporal variation in marine biodiversity of demersal species for community ecology, marine policy and the Scottish fi

In the North Sea, spatial patterns in biodiversity have been identified for demersal fish, epibenthic invertebrates and infauna. For the fish community, species richness exhibits peaks the northern North Sea and in Scottish waters (Reiss et al. 2010). Diversity of fish appears high near major inflows of Atlantic water (Rogers et al. 1995). By contrast, temporal trends in biodiversity are largely unknown. Any investigation of temporal trends in biodiversity must account for strong spatial gradients.

Discarding is the term used where non-target or undersized fish are returned to the sea during fishing. In the North Sea, the high biodiversity of the fish community can lead to substantial discarding of both commercial and non-commercial species. From 2019 onwards, Scottish and other European fishing vessels are unable to discard unwanted catch of commercial species that are managed through setting of total allowable catches, i.e., quotas. The fishing industry is therefore strongly incentivised to avoid unwanted commercial species through better tactical decision making about when and where to fish.

Spatial patterns in fishing and discarding has not been investigated in relation to spatio-temporal trends in biodiversity. Locations that are characterised by consistently high diversity could be expected to have greater potential for discarding, particularly where commercial species are also abundant and fishing activity is high. Overexploitation by fisheries negatively affects biodiversity (Greenstreet & Hall 1996; Coll et al. 2016), leading to changes in fish community structure over time. To aid the fishing industry in understanding spatial structure in the biodiversity as well as their impact on biodiversity, it is imperative to investigate spatio-temporal biodiversity in both the commercial and non-commercial fish community. This knowledge can then be used, in combination with other factors that impact discarding at sea, to describe spatial variation in what we refer to here as discard potential.

Project description

Aim 1 of this PhD project is to estimate biodiversity of the fish community using species richness (R) as a proxy for biodiversity. R will be estimated from scientific survey data that are publicly available from the International Council for the Exploration of the Seas (ICES). Spatio-temporal variability in R will be determined so as to evaluate whether there are consistent 'hotspots' of biodiversity or directional trends over time within the North Sea.

Aim 2 will develop novel metrics for estimating discard potential for the North Sea with the ultimate aim of making these metrics relevant to the tactical decision making about when and where to fish. This metric will be tested against independent estimates of discarding from Marine Scotland - Science. Spatially resolved representations of discard potential will then be compared to data describing actual discarding that available from Marine Scotland - Science who are co-supervisors of this project.

Skills development

Training in the statistical analysis of spatio-temporal fisheries data will be a central part of training. The training budget will also allow for specialised training in the use of fisheries data, for example the courses offered by ICES in Copenhagen.

Benefits

This project offers highly interesting research at the interface of ecology, fisheries science and policy. There is potential for the project to inform delivery of the Marine Strategy Framework Directive given that biodiversity is one of the qualitative descriptors defining Good Environmental Status. The project will liaise with the fishing industry, particularly in assessing their needs for spatial and temporal information.