Scottish scientific electrofishery for razor clams trial - biological and ecological goals: progress report

Executive summary

The electrofishing for razor clams trial started in February 2018 (after public consultation in 2016) and is currently authorised until January 2025. The Science Evidence, Data and Digital portfolio of the Marine Directorate (formerly Marine Scotland Science (MSS)) is responsible for the biological and ecological goals of the trial. These goals are to: gather local level information on razor clam populations and stocks, including accurate data gathered by trial participants to supplement stock survey work; provide advice on sustainable harvesting levels; and investigate the impacts of the electrofishing method on target and non-target species.

Data collected under the trial includes 5896 live razor clams which were dissected and analysed to determine sex, spawning activity, and length-weight relationships. Histological examination of 1468 razor clams revealed evidence of spawning in April and May. Stopping fishing activity during these two months could allow for undisturbed razor clam spawning. Very few undersized (less than 100 mm) razor clams were sampled during this trial, so no results are reported for the suitability of the Minimum Landing Size (MLS) of razor clams.

Fishers and processors submitted self-sample data sheets (razor clam length measurements) which allowed stock assessments to be conducted for razor clams in the Firth of Forth and Firth of Clyde trial areas. Assessment results indicated that razor clams were fished sustainably, with fishing mortality estimated to be below F_MSY (the fishing mortality associated with maximum sustainable yield). To enable regular stock assessments in future, continued data collection is necessary. Mandatory options could be explored for any future fishery as it is unlikely that data from voluntary sampling would be sufficient.

Remote Electronic Monitoring (REM) systems on board participating vessels were primarily used to monitor compliance with the regulations of the trial, but the associated spatial fishery information informed the design of fishery independent surveys and allowed mapping of fishing activity. The mapping informed a survey of razor clams in the Firth of Forth (conducted by the Scottish Association for Marine Science (SAMS)) and enabled stock abundance to be estimated. For the Firth of Forth trial area, the harvest rate was calculated by comparing fishery removals to survey abundance, and was estimated to be 5.7% for razor clams over the MLS of 100 mm.

This trial is an example of collaboration between fishers and scientists, policy makers, compliance officers, and other agencies involved in this work. Regular communication between all parties ensured work progressed and that trial objectives continue to be on track for completion by January 2025. However, the trial would have benefitted from greater engagement between scientists and stakeholders at the start, so that fishers fully understood the importance of data collection and that appropriate scientific resources and staff were available at each stage of the trial.

This trial commenced with clear limits on the number of vessels (controlled by derogation), defined fishing areas (monitored by REM), daily catch limits and effort restrictions (maximum number of days fished). Any future management plans should keep limits under review, alongside regular stock assessments. Stock assessments could be conducted for other trial areas if sufficient data are available in future. Options for reference points should be considered alongside regular stock assessments as part of a fisheries management plan, but key to the success of any future razor clam fishery is the continued engagement between the fishers, processors and all agencies involved in this trial.