CSG 15 Research and Development Final Project Report (Not to Be Used for LINK Projects)

MINISTRY OF AGRICULTURE, FISHERIES AND FOOD CSG 15 Research and Development Final Project Report (Not to be used for LINK projects) Two hard copies of this form should be returned to: Research Policy and International Division, Final Reports Unit MAFF, Area 6/01 1A Page Street, London SW1P 4PQ An electronic version should be e-mailed to [email protected] Project title Archiving and analysis of the MBA bottom trawl and benthic survey data: Unravelling fishing efforts from climate change MAFF project code MF0727 Contractor organisation Marine Biological Association of the United Kingdom, The Laboratory, and location Citadel Hill, Plymouth. PL1 2PB. Total MAFF project costs £ 64,600 Project start date 01/11/00 Project end date 31/03/01 Executive summary (maximum 2 sides A4) Marine ecosystems can alter dramatically over our lifetimes through natural processes or human activities such as fishing, pollution, recreation and coastal development. At present, the factors driving long-term change are poorly understood. A major area of concern is the impact of climatic fluctuations. Over the last twenty years, sea surface temperatures in the English Channel have risen by on average 1ºC, and a global rise in SST of over 1ºC is predicted over the next fifty years. There is convincing evidence that such climatic change can significantly affect populations and distributions of marine species, but to date there is little evidence for changes in demersal fish and invertebrate assemblages within European waters. These communities, important from both economic and ecological perspectives, are however known to be heavily impacted by fishing. Since the onset of commercial trawling, fishing techniques have become increasingly efficient. The effects on many target species have been well studied, but far less is known of the wider impacts on non-target fish and benthic invertebrates. The consequences of climatic change and commercial fishing pose significant national environmental problems to fishery scientists, aquatic resource managers, conservationists and policy makers alike. Only by comparing contemporary resurvey with baseline information within long-term datasets can change be identified. The Plymouth Laboratory of the Marine Biological Association (MBA), founded in 1888, has collected and archived long-term records on a range of variables from the English Channel and Western Approaches over the last century. Data include the composition of planktonic, intertidal and benthic/demersal communities, and measurements of temperature and nutrients. This project is focussed upon MBA long-term demersal fish and benthic invertebrate datasets that have previously resided predominantly in archived notebooks. Primary objectives were to catalogue, archive and enter records onto modern databases, assess their ability to enable us to understand causes of long-term change in marine communities and conduct preliminary analyses to determine whether change has taken place. Demersal fish. The groundfish assemblage off Plymouth has been sampled intermittently between 1913 and 1986. All information from these surveys, including species abundance and length measurements, have been entered onto a CSG 15 (Rev. 12/99) 1 Project Archiving and analysis of the MBA bottom trawl and benthic MAFF MF0727 title survey data: Unravelling fishing efforts from climate change project code database. Resurveys of historic sampling sites have been conducted between January and March 2001, and an ongoing monthly trawl survey has been initiated at station L4 (50°15’N 4°13’W). A summary of the details of the demersal fish database has been placed on the MBA website demonstrating the extent of this archive. Upon request access to the dataset will be granted to interested parties. Details of the archive have also been included in the database of historic trawl records recently compiled by CEFAS Lowestoft within MAFF project MF07-028. Results demonstrate that there have been major changes in the composition of the demersal fish assemblage since 1913, and these changes are consistent with major, ecosystem-level, impacts of fishing identified by analogous studies elsewhere. Mean lengths of fish (Lavg) has shown significant decline, indicating a reduction in the proportions of larger individuals in the community. There were also declines in mean maximum length (Lmax) and mean length of maturity (Lmat) of the assemblage, suggesting a species-level switch to taxa that grow to, and mature at, smaller sizes. In a second level to these analyses, taxa in the community were divided into commercially and non-commercially exploited subgroups. Declines in means of Lavg, Lmax and Lmat were most apparent in commercially exploited taxa. We also detected evidence for significant decline in the mean trophic level of the assemblage. Analyses of community diversity showed no significant changes over time in either species richness, or abundance-based taxonomic diversity (D) or taxonomic distinctness (D*) indices, but significant declines the presence-absence based taxonomic distinctness index (D+), suggesting that closely-related groups are of taxa have declined simultaneously in frequency of occurrence. Taken together, evidence is consistent with patterns expected from the selective, unsustainable harvesting of large, commercially valuable species from high trophic levels. We suggest that means of Lmax, Lmat, trophic level and taxonomic distinctness (D+) may be suitable indices for assessing the impact of fishing on multi-species demersal fisheries. We found little evidence for direct effects of changes in sea-surface temperature on the composition of the groundfish assemblage. Effects of climate change may be difficult to determine on a local scale, due to both climate- and fishery- induced impacts on density dependent natural ecological processes such as competition and predation. Hence, although climate does not appear to necessarily cause direct responses on local population abundance, change may be detectable at the regional scale. Future work is required to examine the effects of broader geographic scale on detecting climate- induced change, in order to determine whether changes in species abundance and/or presence-absence of demersal taxa can be reflective of climatic variability. While we have been unable to detect local-scale changes in fish community structure that have resulted from climate change this does not mean they have not occurred. The detection of factors that operate on a geographic scale is best accomplished using a broad-scale sampling programme. Benthos. The benthic invertebrate fauna of the English Channel were sampled extensively between 1959-85 by the late Dr Norman Holme. Data have largely resided in notebook form or as appendices to publications. These data have been catalogued and archived within the National Marine Biological Library in Plymouth, and assessed for the quality of the data and the potential for re-survey. Three datasets were identified. 1) a quantitative faunal record of echinoderms and molluscs for 324 stations distributed throughout the length and breadth of the English Channel. Other taxa are recorded qualitatively. Sampling was conducted using an anchor dredge that samples both epi- and infauna. In addition Holme compiled references to, or data from comparable historic MBA surveys as far back as 1895. 2) brittlestar survey; mostly quantitative records of all echinoderms from 329 stations on the south coast of England using a mini-Aggasiz trawl, a technique that samples epifaunal more efficiently than infauna 3) death assemblages; a full record of all dead-shell material retained in anchor dredges was made. In addition an extensive archive of videotapes (106), videocassettes (59) and photographic transparency (90 rolls) has been catalogued. The video surveys were made using a towed camera sled. These visual records have been examined and vary in quality, transparencies being far superior to videos. These records can be used to record the presence or absence of larger species and give useful information for habitat mapping. Conclusions and future R&D. These archived demersal fish and benthic invertebrate records are a unique resource within the United Kingdom and Europe with which to investigate long-term changes in demersal ecosystems. Both sets of records form baselines to compare with contemporary resurvey, and enable effects of fishing to be examined, and potentially once appropriate models are developed, climatic change. Results of analyses conducted to date on the demersal fish dataset demonstrate clear patterns of temporal change, there is need to further investigate the patterns demonstrated. We plan a further project / projects in conjunction with CEFAS Lowestoft, to continue to analyse historic data, to continue monitoring the demersal fish assemblage off Plymouth, to resurvey some of Holme’s benthos sampling stations within the English Channel and determine the importance of disturbance and geographic scale in studies long- term change. CSG 15 (1/00) 2 Project Archiving and analysis of the MBA bottom trawl and benthic MAFF MF0727 title survey data: Unravelling fishing efforts from climate change project code Scientific report (maximum 20 sides A4) 1 Project Background 1.1 Introduction……………………………………………………………………………………….. 4 2 Demersal Fish 2.1 Description……………………………………………………………………………..………… 5 2.2 Specific Objectives……………………………………………………………………………….. 6 2.3 Summary of achievements………………………………………………………………………… 6 2.4 Potential for resurvey and

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