Research

In order to be able to successfully manage a fishery it is important to have a good understanding of what stocks are available. To achieve this understanding the Authority has a dedicated research vessel, RV Three Counties, and a staff of research officers who regularly monitor the condition of the stocks within the district. Surveys conducted at sea provide the data that can then be analysed using computer software to create stock assessments.

Cockles and mussels are of great commercial value to the district’s fishermen, particularly in the Wash, so a lot of effort is taken to accurately assess the stocks of these two species. Twice a year surveys are conducted on all of the known cockle beds, while the mussel beds are assessed annually. Cockle surveys are conducted either over the high water periods utilising a Day grab from the research vessel, which takes samples from the seabed at precise locations, or by sampling using quadrats during foot surveys. The extent of these surveys has increased in recent years from approximately 800 sample stations in 2000 to 1,227 in 2010, from which every cockle caught is measured, aged and weighed. The data gained from these surveys is then analysed using MapInfo Geographical Information software from which charts can be produced showing the areas and densities of the stocks over these beds. The information gained from this work is then used directly to facilitate the management of the cockle fishery. A second series of cockle surveys are conducted between October and December to ascertain what impact the previous fishery may have had on the stocks and to determine the extent of any spatfall that may have occurred. Since 2008 additional environmental data have also been collected from the cockle sample sites. This has included collecting information about sediment types and the distribution of lugworm (Arenicola marina), sand mason worm (Lanice conchilega) and Baltic tellins (Macoma balthica).Mussel surveys are generally conducted on foot at low water over a period of two months in Autumn, again the data acquired from these surveys providing information that can be displayed on charts and used to calculate stock levels. In addition to the work conducted on intertidal beds, the research team also undertakes surveys to discover new beds of sublittoral mussels. Unlike those found on intertidal beds, sublittoral stocks do not dry out at low water and are, therefore, more difficult to detect and map. To facilitate the identification and mapping of sublittoral beds, the research team uses RoxAnn Acoustic Ground Discrimination System (AGDS) equipment. RoxAnn analyses the returning echo from the vessel’s echo sounder, and by breaking it down into two values representing the hardness and the roughness of the ground, can be used to graphically illustrate the seabed features. When used in conjunction with Microplot computer software, this information can be displayed instantly as the vessel’s track. This is important because it enables features like mussel beds, which have a distinct RoxAnn signature, to be recognised instantly without the need to undergo extensive reanalysis later.

In addition to finding sublittoral mussels, RoxAnn can also used to identify and map other seabed features such as the biogenic reefs formed by the Ross worm, Saballeria spinulosa. These fragile reefs are an important feature of the marine environment and as such are an interest feature of the Wash and North Norfolk Coast marine Special Area of Conservation (SAC) and the Wash Site of Special Scientific Interest (SSSI). As it is EIFCA’s responsibility to protect these features from fishery disturbance, potentially through a new byelaw, the research team have conducted numerous surveys since 2006 to map the distribution and coverage of the core reef features, providing information to assist the management process. To assist in both the sublittoral mussel and Sabellaria surveys, the research team acquired a Videoray Remotely Operated Video camera in 2007, which has subsequently provided a great deal of video footage of the seabed habitats.Crabs and lobsters are also of great commercial value to the fishermen working in the district. Since 2004 a comprehensive program of surveys have been conducted in order to study these stocks. In addition to studying landing data, this work has involved frequent surveys at sea conducted aboard commercial fishing vessels. These surveys have allowed thousands of crabs and lobsters to be measured, and unlike landings data, has enabled a population distribution of under-sized individuals to be ascertained. Between 2004-2006 approximately 2,500 lobsters were also tagged and released, allowing an insight into their growth and movement patterns to be determined from re-captured individuals.In order to protect the sustainability of the crab and lobster stocks, the Committee has a byelaw preventing the removal of berried (egg-bearing) females from the district. Although berried females are easy to spot, some fishermen are known to scrub the eggs off berried individuals making detection difficult. In order to counter this problem, in 2005 the research team developed a chemical test that can be used to detect when the eggs have been scrubbed off such individuals. After thoroughly testing the technique over a two-year period, the test led to a successful conviction in 2007 in which a fisherman was found guilty of scrubbing fifteen berried lobsters. More recently a smaller, more mobile version of the test has been developed and demonstrated to other Authorities that enforce a berried hen byelaw.Although the majority of the work conducted by the research team involves monitoring of stocks, original research work is also conducted. Following the introduction of hydraulic suction dredges to the cockle fishery in 1987 there have been concerns about the survival rates of discarded individuals. Since 2000 the research staff have closely monitored the discard breakage rates and have conducted experiments to determine the mortality rates of discarded individuals. This work culminated in 2008 when discard mortality rates were determined for the cockles discarded from the dredge head itself. Through this work it has been possible to determine the additional incidental mortality that the dredge fishery can incur, and thus best advise the managers on which beds to open or keep closed. Similar impact assessments were conducted in 2009 and 2010 to determine whether the handwork cockle fishery was having an adverse impact on the ecology of the site. The latter study involved collecting core samples from fished areas and unfished control sites, over a four month period to ascertain to what extent the fishery had disturbed the site, and the rate of subsequent recovery. This study found that, barring the targeted cockles, the fishery had caused no significant disturbance to either the other infaunal species or to the substratum.In 2008 cockles on the intertidal beds began to suffer unusually high mortality rates, during which approximately 14,000 tonnes died during the course of the year. Although the cause of the mortalities were unknown, the symptoms were similar to those that had been reported annually from the Burry Inlet since 2004. As combined cockle and mussel stocks were particularly high in 2007, it was thought that localised food limitations could potentially be responsible for the deaths. To examine whether this could be the case, the research team instigated a long-term programme to monitor the levels of Chlorophyll-a (a proxy for algae) at various locations around the Wash. The short term aim of this programme was to determine whether food limitations could have been responsible for the cockle mortalities, with a more ambitious long-term aim of ascertaining localised shellfish carrying capacities within the Wash. Unfortunately, this latter goal, which would require external help with the modelling of the hydrology and food webs of the site failed to secure necessary funding to support the proposed Fellowship project post.

In addition to our own core monitoring and research work, the Committee also assists other scientific organisations conduct their work in the area. Over the years this has included assisting Newcastle University (on behalf of English Nature) to conduct broadscale seabed mapping, CEFAS to conduct annual razorclam surveys and the Centre For Ecology and Hydrology to conduct bird counts and invertebrate surveys. Water and biological samples are also collected every month for the Environmental Health Organisation so that the water quality can be monitored. Plans are being developed so that from 2011 onwards EIFCA will begin conducting juvenile fish surveys in some of the estuaries within the district, potentially feeding data into the Environmental Agency’s Water Framework Directive.


Research Reports

 

 

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