Past Helford VMCA events
The National Lobster Hatchery --- the future
Sat 20 Feb 2010 Dominic Boothroyd
Starting with a global perspective, Dominic Boothroyd told us that the world’s population of some 6 billion people is expected to rise to over 9 billion over the next 40 years, with the largest increases being in Africa, Asia and Latin America. Such growth will not only require the production of more food but could also increase the demand for protein, including a higher demand for sea food. However, production from the world’s wild fisheries is not increasing. About 75% of fisheries are categorised as fully exploited, over-exploited, depleted, or in a state of recovery, with some prominent examples being the European eel, Grand Banks cod fishery and the Norwegian lobster fishery. The remainder are classed as under-exploited or declining. Hence meeting an increasing call for fish will depend largely on the success of fish farms, producing trout, Tilapia, carp, etc, and stock enhancement programmes, in which cultured juveniles are released into the wild to augment existing stocks. For several historical reasons stock enhancement has not been seen in a positive light, in Europe and the USA for example. Norway operated a cod stock enhancement programme for many decades, but due to a lack of appropriate monitoring it remains uncertain whether it was successful. Some parts of the world have adopted stock enhancement with great success. The world leader here is clearly Japan, which has invested heavily in the techniques, involved university scientists and fishermen and now has some 16 national hatcheries and 57 local government hatcheries, which have together released many billions of juveniles covering about 100 species. The details are impressive. In just one year, Japan released 76 million juveniles of 37 fish species, 221 million juveniles of 12 crustacean species, 3,213 million juveniles of 26 mollusc species and 78 million juveniles of 8 invertebrate species. Intensive studies have helped to develop optimum culture and release strategies. For example, maximum impact on the scallop stocks is achieved by releasing the spat when they are 1 year old.
The contrast between Japan and the UK could hardly be more stark. This country has 2 lobster hatcheries, at Padstow and Orkney, with some additional releases from an aquarium on Anglesey. Previously there were three more: Conwy, Ardtoe and Orkney; and a few others are proposed, e.g. Sheringham, North Berwick. Fisheries are of great importance to Cornwall. It has a coastline of 326 miles, about 50 ports, a few fish markets, e.g. Newlyn, Looe and a poorly developed rural economy. There is a substantial reliance on shellfish, including crustacea, with a large percentage of the catch being exported to the continent, to the value of £1.8 million in 2005. Cornwall has about 10% of the UK’s under-10 metre boats, exploiting over 50 species of fish and 4-6 species of crustacea. The boats, with crews of 2 or 3, can deal with 400 to 1000 pots and in 2005 there were 400 shellfish permits, with around half-a-million pots in operation.
From the 1960s onwards there was a spectacular collapse of lobster stocks in Norway. The catch dropped from 1400 tons and is now only about 30 tons per annum. Cornwall saw declining stocks in the 80s and 90s and Cornwall Sea Fisheries Committee, who are responsible for managing the fisheries out to 6 nautical miles, took action, increasing the minimum landing size (MLS) and closing the fishery for egg-bearing females. The increase in MLS allowed more lobsters to breed before they could be landed, whilst the embargo on egg-bearing females served to protect the next cohort of youngsters. In addition, the Chief Fisheries Officer proposed the setting up of a lobster hatchery. The chosen location was Padstow, a centre for the North Coast fishery and also for tourism. Funds were raised from the European Community, councils and businesses, such as Tesco and the building was completed in 2000. Initially run as a non-profit organisation, the hatchery became a charity in 2005.
Research over 25 years in both Norway and the UK demonstrated that, although it was possible to raise lobsters from egg to adult, it was economically unviable due to the cannibalistic nature of the animals and because of their slow growth rates (taking 3-7 years to reach market size). However, after the larval stages the creatures burrow and animals released at this point, in trials in the UK and Norway, showed very high survival rates. A Norwegian study revealed that a large percentage of the animals caught in the fishery were hatchery-reared, indicating that in depleted fisheries restocking can be extremely effective. This, combined with the fact that lobsters rarely move more than 5km from their release site, makes them an ideal candidate for stock enhancement, restocking and marine ranching programmes.
The aims and activities of the National Lobster Hatchery (NLH) focus on three broad areas: stock enhancement, education and research. Stock enhancement is a charitable operation in which post-larval juveniles are released at chosen sites, at no charge, to restock depleted areas with the aim of ensuring long-term production. About 65,000 juveniles have been released to date, at a rate of 10-20,000 per year and it is hoped to increase this to 40-50,000 per year in the future. Release sites are scattered around Cornwall and the Scillies (800 releases in the Helford last year). Local fishermen advise where to find optimum sites, where the sea bed is sand or silt with scattered rock, allowing the juveniles to burrow safely.
Egg-bearing female lobsters, caught by fishermen in the May-October season, constitute the broodstock at the hatchery. The larvae which hatch from the eggs are reared in cylindrical kreisel cones holding about 2000 individuals, with upward currents to keep them in suspension. Predation can be high. After 14-18 days, now looking like lobsters, the individuals can swim to find burrowing points but are reared for an additional 3months (under ideal conditions) and are then ready for release. Here there are several options. One method is the Tube release system where animals are delivered directly to the sea bed from a fisherman’s boat. Another utilises a plastic box which is planted inside a fisherman’s holding cage and then placed on the sea bed. This has a time release mechanism which breaks after a period of time, liberating the juveniles directly into the fishery.
With its location in Padstow, a popular tourist venue, the NLH receives 40,000 visitors a year and can pursue an educational role by increasing public awareness of lobsters and sustainable fishing. Additionally it has programmes involving schools, colleges and universities, at all levels from primary to postgraduates and including students from abroad. The hatchery’s research programme, often in conjunction with MSc and PhD students at the University of Plymouth, covers a wide range of topics, because much remains to be discovered about lobsters. For instance, little is known about the life stage from 5 weeks to 2 years, when the animals are burrowed in the sea bed, or of their diet, or of diseases (only one viral and one bacterial disease have been documented as being of commercial significance). Projects include studies of prebiotic and probiotic diet components; the effects of ocean acidification on the exoskeleton; artificial habitats; and disinfection regimes in larval rearing. It may be possible to rear larvae in cages hanging off mussel rafts, the larve obtaining their food from the sea water instead of the pellets that are used in the rearing cones. The overall aims are to increase production and survival rates and to have a means of monitoring the success of releases.
A key issue for the charity is how to fund the production and release of large numbers of juvenile lobsters. Income is derived from a variety of sources, mainly the visitor centre but also from the shellfish training centre, research/education grants, shop/web sales, corporate members, donation schemes and product development. These, augmented by other possible revenue streams, will hopefully allow the business to be enhanced, further development of the site and the development of saleable products, such as feeding pellets.
The HMCG wishes to thank Dominic Boothroyd very sincerely for his detailed and highly informative talk and his corrections to the above report.
Paul Garrard
Cornish Dolphins – an update Dr Nick Tregenza
23rd January 2010
In his talk to an appreciative audience of 57, Dr Tregenza began with the largest cetaceans, the whales, showing photographs of stranded animals, alive and dead, and mid-water sightings. It was a surprise to hear of the great variety of whales which have been recorded in Cornish waters, for example a Baleen whale at Sennen, Fin whales around the Lizard and Lands End and Sei whale in Carrick Roads. Sightings of Fin whales over the last 10 years may reflect growth in the population since it was cut by more than 90% by commercial whaling, which ended in the 1980s. Strandings of Minke whales have been recorded and these are seen regularly. Sowerbys Beaked whale, an animal that can dive to depths of 2-3 km, is rarely seen from the coast, but there have been live sightings in Falmouth Bay (reported by fishermen as crocodiles). Pilot whales are more often seen. Orcas also visit Cornwall and there have been 30-40 sightings. They tend to associate with basking sharks and have been observed to tear them apart as food.
The commonest cetaceans are Common dolphins, often seen by fishermen 2 or more miles offshore but rarely in shallow water. Hence the tragic stranding in June 2008, when 26 healthy Common dolphins died in Froe Creek, was a most unusual occurrence. A naval exercise using anti-submarine sonar had ceased earlier, but helicopter noise may have been contributory in driving the animals inshore in panic. Such mass strandings are very rare. One involving Long Finned Pilot whales occurred in Mounts Bay in 1905 and there was a near-repeat in 1962, when the whales entered the Helford and Gillan Creek but were driven back to sea.
The Harbour porpoise is the smallest of the cetaceans, but widespread, extending to Greenland. Sightings decreased from 1955 onwards, caused by the agricultural use of organo-chlorine pesticides. Entering the marine environment via surface run-off, these pollutants move up the food chain from algae to fish to cetaceans and other animals and, as they are soluble in fats, the chemicals become concentrated in the female’s milk and are transferred to the babies. As a result, although the females became relatively unpolluted, the death of contaminated males and babies damaged the breeding process. The pesticides were eventually banned, except for daffodil growers who claimed exemption to combat Narcissus bulb fly, but even they were forced to concede after a campaign by CWT and others exhorted children to ‘buy chocolates not daffodils’ for Mothers’ Day! The well-being of peregrine falcons, otters and cetaceans subsequently improved.
Accidental entanglement in fishermen’s nets, known as the by-catch problem, is a serious issue for dolphins and porpoises, with the animals suffering injury and death. Over 2000 by-catch incidents were recorded by Cornish and Irish fishermen each year. They occur all over the Celtic Sea, showing that the creatures occupy shelf waters, not just coastal zones. In an attempt to understand and reduce the death toll, devices which recorded cetacean communication sounds were developed by Dr Tregenza. The POD (porpoise detector) is housed in a cylinder and installed on the sea bed. A smaller, ‘bomb-like’ version can be attached to nets. The instruments record the presence and number of cetaceans and can help to chart their movements. Porpoises are known to have moved southwards since 1994, increasing the numbers found off Lincolnshire and East Anglia and in the Celtic Sea. This movement is probably a response to shifting fish patterns. PODs have been used in the Sea of Cortez, Baja California, where by-catch has reduced the Vaquita, a small endemic porpoise, to 200-300 individuals; and in New Zealand, where inshore gill net fishing has been restricted to halt the decline in Hectors dolphin.
Another important instrument is the Pinger, which emits a sound pulse every 4 seconds. In trials under the auspices of the Cornwall Wildlife Trust, four fishermen have attached pingers to some of their nets. These act as a warning to cetaceans; and accompanying POD records show that fewer porpoises are detected in the vicinity when pingers are employed. Freed of the stigma of cetacean by-catch deaths, the fish catch can be marketed at better price as environmentally-conscious (Pisces project) and the fishermen now want to attach pingers to all of their nets. Other fishermen contend that the pingers do not work, or break, and work is in hand to develop a more robust version.
Although pingers are effective in reducing porpoise by-catch, the evidence is uncertain in relation to dolphins. Common dolphins get caught in nets not infrequently and Bottlenose dolphins are now present in such small numbers that by-catch trends are impossible to evaluate. Past observations record how Bottlenose dolphins would drive fish into Hooe Lake, Plymouth, then wait for the tide to fall to catch them as they swam out. Then Bottlenoses disappeared, apart from a few lonely individuals, and did not reappear until 1991 when a pod of about 20 arrived, probably after splitting off from a more distant group. Now they have been reduced to perhaps 10 and are on the verge of extinction. These are the inshore form of the species and have been recorded from Dorset around Cornwall to Ilfracombe. An offshore form exists in larger numbers, mainly along the edge of the continental shelf. Bottlenose dolphins sometimes play with surfers and swimmers and have a similar life-span to ours. They are highly intelligent creatures with exceptionally strong social structures. They are one of the few animals which can recognise themselves immediately in mirrors. In a comparison of brain size relative to body mass, man registers as 7.44, dolphins 5.31, chimpanzees 2.49 and dogs 1.17, but if only lean body mass is used dolphins and man are very close together.
The key issues which have faced the cetaceans have been (1) organo-chemical pollution, the reduction of which is now showing some success; and (2) fishery by-catch, which hopefully can be reduced by further development of pingers and fishery management measures. The animals most at risk and in danger of disappearing entirely are the inshore Bottlenose dolphins.
On behalf of the HMCG, I would like to record sincere thanks to Dr Tregenza, not only for his absorbing talk but for helpful corrections in the above report.
Paul Garrard
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