Fisheries

We have been undertaking fisheries work for the past 25 years and are proud to have been retained by the Broads Authority as expert advisors throughout this period as a result of our unrivalled UK experience and expertise of biomanipulation (restructuring) of fish communities as a tool for restoring shallow lakes. Our ability to survey fish effectively is underpinned by in-depth understanding of both coarse and salmonid fish in lacustrine and riverine environments.

We have enormous practical experience of a range of standard quantitative and/or semi-quantitative techniques including seine netting (lakes), three-catch depletion by electric fishing both by wading and aboard boats (streams and rivers) and trawls (large lakes and rivers). In relation to surveying deep lakes we have established links with a well-respected specialist in hydroacoustics. We also occasionally use more qualitative methods such as shoreline electric fishing (lakes and rivers), fyke nets (lakes and ponds) and angling catches (all habitats) to provide information on specific parts of the fish stock.

In addition, we have championed the use of point abundance sampling by electric fishing (PASE) in shallow lakes, wetlands, streams and rivers. This method comes into its own in vegetated habitats where it becomes virtually the only means of generating a quantitative estimate. Although widely accepted as sampling young or small fish effectively, our work shows that PASE may also be surprisingly good at sampling large individuals, although care must be taken in interpreting the biomass estimates produced as a result of the high variance around the mean.

Our extensive knowledge of fish sampling methods meant that we were recently engaged to design a fish sampling methodology for SSSI lakes (Sites of Special Scientific Interest) on behalf of Natural England. We are now in the process of putting that sampling design into practice at 20 lakes of variable depth and size around England. It has been our pleasure to collaborate with Dr Ian Winfield, lake specialist at the Centre of Ecology and Hydrology, on both projects.

Sampling fish extends to catching fish on a large-scale and we are well-known as being the most successful and experienced practitioner of biomanipulation in the UK, notably in the Norfolk Broads on lakes from 5-55 ha as well as experimental exclosures within lakes. We have manipulated fish populations through removal of undesirable zooplanktivorous (e.g. small Roach) and benthivorous (e.g. large Bream or Carp) elements of the fish stock, coupled with retention and/or stocking of piscivorous species (e.g. Perch and Pike) or fish that would be seen as being part of the desired fish community (e.g. Tench and Rudd).

The wholesale nature of fish removal, involving >100,000 fish in some cases, has been achieved to the highest welfare standards, with fish quickly translocated to suitable receiving waters. Biomanipulation requires innovation in the choice of methods and at Ormesby Broad we developed and used a 'scare-line' of coloured 'kite tails' towed between two boats in large lakes to drive fish large distances into a net trap for subsequent removal. In this way, we caught >400 adult Bream in a matter of a few hours.

Freshwater fisheries surveys and management is carried out for a range of clients from water companies to conservation organisations. We are regularly contacted about survey work that is technically difficult or physically demanding as we specialise in finding a safe, effective solution to a sampling problem. To this end, we often work with gear suppliers to find a bespoke design solution. We also adhere to our own code of practice of operational procedures of the highest standards as well as fully complying with any relevant legislation or guidelines, such as the Environment Agency's code of practice for electric fishing.

We have recently branched into marine fisheries work aboard chartered commercial survey and fishing vessels from 10-30 metres in length. The experience of our staff in designing appropriate monitoring programmes and managing survey logistics is essential to successful delivery of a project. The work itself has ranged from the use of a small (1 m width) bespoke surface larval trawl designed to survey prey available to diving Little terns to the use of a full-scale commercial benthic sandeel trawl of 100 m in length towed over 10 km.

Other work has included spawning surveys for Atlantic Herring, again using equipment designed specifically for the purpose, and most recently, sampling harbours and salt marsh creeks with seine nets, where we have captured a wide range of fish and invertebrates such as shrimps. We also have links with a number of experts who are pioneering acoustic and video monitoring techniques and could employ these where required along with beam trawls, grabs, pots and drift nets.

 













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