Managing fisheries at an ‘optimal’ level could offer long-term benefits to fishermen and the environment

A local Lyme Bay fisher hauls his potting gear

At around 7 years from conception to publication, our research takes time. But that’s exactly the point. When we were first approached by the Blue Marine Foundation and local fishermen of Lyme Bay, concerned about the potential impacts associated with an increase in static potting in response to mobile fishing being banned from inside the Lyme Bay MPA, we knew a multi-year study was required. Learning from the ongoing recovery monitoring that took 4 years to detect first signs of ecological recovery and which, 13 years on, is still teaching us new things about the responses of the ecosystem, the experimental potting study was developed. Over 4 years we intended to experimentally control potting effort inside the MPA in order to assess the impacts of parlour potting on the ecosystem.

Fishing News headline at project launch

Beginning in 2014 we manipulated potting densities inside treatment areas, with the help of local fishers, introducing a gradient of potting effort from no potting (control areas) through to low, medium, and high levels of potting effort. Inside these areas, using a range of survey methods, we assessed changes in benthic reef building and reef associated assemblages, plus changes in the local crab and lobster fishery (the species primarily targeted by potting in Lyme Bay), in response to increasing potting pressures.

The densities used in the high treatment were considered to represent maximum fishing effort. Current levels of pot fishing effort inside the Lyme Bay MPA were characterised by the medium density. Low pot densities were also considered to replicate the pot fishing effort in some locations of the Lyme Bay MPA and were considered a level of pot fishing more similar to that of pre-closure. Controls, where pots were removed to simulate a ‘no pot fishing’ treatment, were incorporated into the study as a reference point to determine baseline changes, and fishermen maintained these as no-take zones throughout the study.

Now, this research has been published in Scientific Reports, a journal published by the Nature group. After 4 years we found that in areas of higher pot density, fishermen caught 19% less brown crab and 35% less European lobster, and their catches of brown crab were on average 35 grams per individual (7%) lighter. The effect on marine species was also significant with two ecologically important reef species, Ross coral (Pentapora foliacea) and Neptune’s Heart sea squirt (Phallusia mammillata), 83% and 74% less abundant respectively where pot density was higher.

Defining a threshold for sustainable fishing animation

The study provides evidence the first evidence of its kind, that a pot fishing intensity ‘threshold’ exists while commercial pot fisheries are likely to be compatible with marine conservation when managed correctly at low, sustainable levels. Our results indicate that a low-effort high-reward strategy works for both fisheries and conservation. The ecosystem effects of all commercial fishing methods need to be fully understood in order to manage our marine environments more effectively and so this evidence is a significant step towards developing well-managed fisheries inside Marine Protected Areas

Parlour pots in Lyme Bay

In a time where Covid-19 and BREXIT are impacting an already uncertain fishery, and with a number of reports highlighting that many crab and lobster fisheries around the UK are close to overexploitation, this new evidence will hopefully help inform discussions regarding making changes to these fisheries that will help secure their long-term futures.

This project was funded by the Blue Marine Foundation and the Department for Food and Rural Affairs (Defra). We want to champion the local fishers of Lyme Bay for the involvement in this project, without which this project would never have been possible. Facilitated through the Lyme Bay Consultative Committee, this partnership between us and the local fishermen is built on years of trust which has developed as a result of their direct involvement. Something we strongly believe is a successful blueprint for research of this kind and promotes local stewardship.

‘Optimal fishing effort benefits fisheries and conservation’ visual abstract

Lyme Bay Case Study Film from Blue Marine Foundation on Vimeo.

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