The European spiny lobster (Palinurus elephas), referred to as ‘crawfish’ throughout this report, is distributed across the Southwest of the UK,along the west coast of Ireland and into Scotland. A large number inhabit rocky ground in the Isles of Scilly Inshore Fisheries and Conservation Authority’s (IoSIFCA) District. The crawfish fishery in the Isles of Scilly accounted for 12 percent of total fish landings in 2022 and is currently targeted by 60% of boats in the fleet. Landings have increased by 275% in the past 4 years, with yearly value increasing by 241%, from just under £67,000 in 2019 to £162,000 in 2022.
Crawfish are an omnivorous crustacean, with a wide-ranging global distribution in northern temperate waters in the Eastern Atlantic Ocean and the Mediterranean Sea. They live in reef habitats at depths ranging from 15 to 90 metres. They have a long planktonic larval phase which lasts ~ 9 months in the Atlantic before settling. It is believed they take around 7-8 years to become sexually mature, however data on growth and settlement is lacking in the Atlantic populations. Studies have found individuals mostly remain within a few kilometres of their home reef, however some undertake long distance movements. The reasons for this are still unclear.
Crawfish are a non-quota, commercially valuable species. There has been a targeted fishery for over 100 years, which saw a collapse in the late 1900’s across its range.(2013), due to reductions in the population based on historical abundance and exploitation levels. The Isles of Scilly crawfish fishery was first recorded in the 1920’s, with overfishing depleting the population in the 1920’s and 1950’s. The species has been slowly recovering throughout South West England. Landings on Scilly remained steady from 1998 to 2018 and have since increased by an average of 40% a year (30% in 2020, 75% in 2021 and 20% in 2022). Management in the IoSIFCA District in 2023 is through a minimum size of 110mm, which was bought into effect in 2020 and a prohibition on landing of berried females.
This crawfish report is based on catch recording onboard commercial vessels in the Isles of Scilly fleet. Beyond this there is scope to continue onboard catch recording every 3 years, with the aim to increase data on the fishery to develop indicators from which the fishery can be more effectively monitored and managed.
One local fisherman concluded that there were six key items to take away from the report:
1. Craws take take 7-8yrs to reach 110mm
2. The current ‘boom’ recruitment is first in 40yrs - hopefully the first of many but without trying to manage it that’s a high risk gamble on nature coming up with the goods.
3. Any management needs a clear objective
4. Regular ‘real time’ fisheries monitoring is needed
5. Fisheries management trigger points and limits need to be put in place
6. Future lies in the hands of the fishers - chose boom and bust or demand long time properly managed fisheries
Findings from the IFCA report were then matched against the Seasonal Closure Consultation report:
And, from those key findings he concluded that:
The overall objective should be for a co-management approach in which fishermen and regulators are working in tandem with scientists and using knowledge collected to determine whether and what management intervention is required.
Crawfish research over the last two years in collaboration with fishermen provides a first and basic indication that the population is healthy. Catch Per Unit Effort is increasing; there is an even population size distribution and the average size of males increasing by 4mm since 2015. However, average size of females is decreasing and this species is known from history to be vulnerable to sudden declines. Although effort has increased rapidly within the district over the past three years, there are no signs that would indicate effort is unsustainable. However, the study is still at a very early stage and sample sizes are very small to have high confidence in CPUE and size distribution. It is important to note that it is not possible, with two years of data to determine a trend.
Based on this knowledge, it would be sensible to ensure annual onboard research with a target of 20-30 trips a year and to continue to use baited video to replicate our understanding of populations on the ground. Diver surveys have been used in the past, but it would be beneficial to incorporate an additional element to record the sex of individuals.
In collaboration with fishermen, the development of some target indicators or 'warning lights' would be useful - for example if the number of boats or tiers increases by 20%; the number of immature fish declines by 20%; catch per unit effort declines by 15% or the average size of individuals declines by 15%. Any of these would be a point that would initiate meetings with fishermen and IFCA to discuss whether any further measures would be necessary.
Research should aim to achieve a higher rate of sampling over greater time.
It is not only in Cornwall that concern has been raised over the management of the vulnerable crawfishery. An eleven year programme off the Brittany coast and the Il de Sein has come up with similar concerns AND some suggestions for steps taken to reduce the likelihood of a stock collapse such as was witnessed off cornwall in the late 1970s - bearing in mind that it has taken until the early 2020s for the stock to recover sufficiently for it to be fished commercially again. (Ed)
NB All the following has been translated from the original French website.
This program was set up at the request of professional fishermen who noted significant catches of juveniles during the winter of 2014. Started in early 2015, the red lobster reconquest program began with actions to mark oversized lobsters caught by professionals. Throughout the year, around forty vessels involved in the program marked nearly 3,000 lobsters along the coastline from Cherbourg to Saint Jean de Luz.
The first results
Thanks to the marking and sampling work carried out by professionals, an initial inventory of the presence of lobsters was able to be carried out. The results show that the red lobster is present throughout its historical distribution area. Of course, some areas historically known for high abundance are now less productive than before. However, it is important to emphasize that the red lobster is currently "recolonizing" all the areas where it was present.
For the moment, a huge number of juveniles (cephalothoracic size less than 11 cm) have been observed and marked.
Concerning the markings, the recapture rate of lobsters is 5%. This rate, which may seem low, is within the norms concerning the captures/recaptures of crustaceans. These first recaptures do not allow us to draw generalized conclusions. However, it was observed that some marked lobsters were relatively sedentary while others, in smaller numbers, had much more significant movements of up to several tens of nautical miles.
Concerning growth, the data collected are still a little low to establish a growth curve. However, for juveniles, we note a growth (cephalothoracic) of approximately 10 mm per moult.
Upcoming work
In 2016, tagging operations will continue with all volunteer vessels that fish for lobster regularly or occasionally.
To better characterize the size classes present in all sectors, volunteer vessels will be able to self-sample all of their catches. The aim of this operation is to achieve a better understanding of the species at different stages of their life and to characterize their habitats.
Work on habitat characterisation using the empirical knowledge of professionals will also be carried out across the entire study area.
Contact Erwan Quemeneur via our contact form by choosing the subject "Tagged species".
Sure! Here are the answers to your questions along with their translations in English.
Summary of the Report
The report presents the advancements of the monitoring program for the Red Lobster (Palinurus elephas) in the marine protected area (MPA) on the Chaussée de Sein after eight years of observation. It highlights a collaborative study involving researchers and institutions, utilizing various methods to assess the abundance and dynamics of the lobster population, while paying special attention to the growth and movement of the species.
Methods Used to Monitor the Abundance of the Red Lobster
To monitor the abundance of the Red Lobster, several methods were initially discussed, including experimental fishing with nets or traps and diving surveys. A standardized protocol was established to ensure that follow-ups were consistent from year to year. The main methods included:
- Net Fishing: Utilized a one-kilometer-long trammel net with a stretched mesh size of 260 mm, which is commonly used by fishermen targeting lobsters. The nets were deployed for 48 hours to measure abundance rather than to maximize catches.
- Trap Fishing: Two campaigns using traps were conducted between 2009 and 2014, though initial traps were found unsuitable for targeting lobsters. The increase in abundance observed with nets prompted a renewed focus on trapping in 2014.
- Diving Surveys: Conducted to complement net fishing, allowing researchers to study individuals not yet visible to the fishery and to access areas not reachable by fishing gear.
Primary Results Regarding the Growth of the Species
The monitoring has shown a steady increase in average abundance per deployment since the start of the program. Notably:
- The average abundance has regularly increased, particularly after the establishment of the MPA, which positively influences the lobster population.
- The report also discusses various aspects of the lobster's habitat and the types of structures that provide shelter, indicating a range of preferred microhabitats for different size classes.
The overall findings suggest that the conservation measures in place have been beneficial for the lobster population, allowing for better growth and sustainability.
The report highlights several findings associated with managing a strong stock of the Red Lobster (Palinurus elephas), which include particular actions taken regarding tagging, size management, and sex distribution:
Findings Associated with Managing a Strong Stock
1. Tagging and Marking:
- All caught or observed lobsters were sexed, measured, and tagged. This process included the use of spaghetti tags and electronic chips, enhancing the ability to track individual lobsters over time.
- Tagging strategies were improved based on research, with marks being inserted in specific locations to minimize loss during molting.
1. Size Management:
- The study observed a clear distinction in the size distribution between males and females. Males typically reached larger sizes, with a peak around 150 mm, while females peaked at around 130 mm.
- Young lobsters (below 110 mm) began appearing in catches from 2011 onwards, indicating a strong recruitment into the fishery, which is essential for stock sustainability.
- Management actions may include returning smaller lobsters or limiting catches to protect juvenile populations, although specific details on returns are not explicitly mentioned.
1. Sex Ratio Monitoring:
- The sex ratio was monitored, showing that larger sizes were predominantly males. This suggests a potential strategy to implement size restrictions that favor the preservation of female populations, as they can be crucial for reproduction.
- The low number of females recaptured poses challenges for assessing female growth, indicating that targeted management practices could help in balancing the sex ratio and ensuring a sustainable breeding stock.
1. Stock Assessment Metrics:
- The analysis of stable isotope ratios in hemolymph helped to understand the trophic positioning of individuals and can guide management decisions regarding habitat protections based on dietary sources.
- Continuous monitoring and assessing size classes of lobsters, especially within the ages of 0 to 3 years, are critical for establishing a long-term monitoring framework to ensure that growth rates and age distributions are optimal.
1. Collaborative Learning:
- The integration of experiences from similar studies in other regions (e.g., Australia) facilitated improvements in methodology and understanding of lobster dynamics, which can inform management actions.
Actions Recommended for Strong Stock Management
- Enhancing Tagging Protocols: Continue using both traditional and electronic tagging to effectively track population dynamics.
- Implementing Size Limits: Consider implementing regulations on size limits for catches to protect juvenile lobsters.
- Maintaining Sex Balance: Develop strategies to ensure a balanced sex ratio, which is crucial for reproduction.
- Increasing Research and Monitoring: Maintain ongoing research to monitor growth rates and establish a robust understanding of population dynamics and habitat requirements.
These findings reflect an integrated approach to managing the stock of Red Lobsters, balancing immediate fishing needs with long-term sustainability goals.
