When does fishing lead to more fish? Community consequences of bottom trawl fisheries in demersal food webs

P. Daniel van Denderen, Tobias van Kooten and Adriaan D. Rijnsdorp of the Wageningen Institute for Marine Resources and Ecosystem Studies and Wageningen University in the Netherlands carried out the research for their paper in the Proceedings of the Royal Society B today. They entitle it, "When does fishing lead to more fish? Community consequences of bottom trawl fisheries in demersal food webs." 

What the authors discovered is that the long-term effects of trawling increase fish and probably benthos mortality. In one form of bottom-up community(see later), fish predation doesn't affect the benthos community to any great degree, but the trawling does and also increases fish biomass. What could be done next is to consider the edibility of the benthos to fish, but it seems that the models don't produce any different results if the attractiveness of these invertebrates is varied. Other models have found the same result. Either the reduced fish predation or the resultant competition somehow increase the biomass of the invertebrates on the bottom, especially annelids, although it has been impossible to find out which of these two factors cause the polychaetes and other annelids to increase. Large bivalves and several other bottom species are a different kettle of fish. They are definitely reduced in numbers by trawling. 

Technical changes in trawling are essential to prevent such high mortality, unless the trawlers are prevented from fishing altogether. Fish abundance and yield is shown to be reduced when these measures are taken however. In the North Sea, it's been assumed that primary productivity can increase when the bottom is disturbed or "discards" could help scavengers to increase their particular biomass. 

What the authors conclude is that the state of the ecosystem is crucial. What they refer to as a "top-down" system is more prevalent in some areas such as the Irish Sea, where fish are still quite numerous and control the prey numbers. In bottom-up systems, the fish have often been exploited by fisheries, as in the southern North Sea. The invertebrates are not predated as much and their nutrient resources seem to determine how the ecosystems operate. That means that the positive effect of trawling on some benthic invertebrates would only apply at high trawling frequencies. 

Change in fishing gear in such areas would be necessary to prevent depletion of the rest of the benthos - the large bivalves that are decimated by trawls. Then we would see if the dream was true, more fishing produces more fish, but only in these specialised and over-fished circumstances!

Article courtesy of the Earth Times:


This the abstract taken from the the Royal Society.

"Bottom trawls are a globally used fishing gear that physically disturb the seabed and kill non-target organisms, including those that are food for the targeted fish species. There are indications that ensuing changes to the benthic invertebrate community may increase the availability of food and promote growth and even fisheries yield of target fish species. If and how this occurs is the subject of ongoing debate, with evidence both in favour and against. We model the effects of trawling on a simple ecosystem of benthivorous fish and two food populations (benthos), susceptible and resistant to trawling. We show that the ecosystem response to trawling depends on whether the abundance of benthos is top-down or bottom-up controlled. Fishing may result in higher fish abundance, higher (maximum sustainable) yield and increased persistence of fish when the benthos which is the best-quality fish food is also more resistant to trawling. These positive effects occur in bottom-up controlled systems and systems with limited impact of fish feeding on benthos, resembling bottom-up control. Fishing leads to lower yields and fish persistence in all configurations where susceptible benthos are more profitable prey. Our results highlight the importance of mechanistic ecosystem knowledge as a requirement for successful management."

Eating at its best - eat local fish!

Great to see one of Penzance's eating places with fish out front on their specials menu board - though at £14.95 that mackerel is going to have to have exceptional!

What do they serve at London's Smithfield Market?

Why Cornish hake of course!

On the dining room menu board at 'Smiths' of London's Smithfield Market - great to see our very own Cornish Hake supplied courtesy of the Ajax actually named as the supplier!...

looks delicious Matt!

The devastation of a fishery shows the idiocy of much environmental politics

WHEN Bagehot’s grandfather built a house in Carradale, a village on the Firth of Clyde, around 20 tubby fishing smacks operated from its tiny harbour. It was the 1960s and the fishing had never been so easy. Equipped with diesel engines, sonar fish finders and heavy trawl mesh, the boats were scooping up herring by the shoal. They employed over 100 men, from almost every village household. You would see them from the house, steaming home across the Kilbrannan Sound with a confetti of white seagulls over their bows.

Prawn trawlers in Girvan Harbour - 1982

For two decades the bonanza on Scotland’s west coast continued. An occupation that had been seasonal and modestly profitable became year-round and lucrative. Baskets of herring put televisions into fishermen’s cottages and cars outside their doors. But fish, like oil and gas, with which Scotland’s continental shelf is also well-endowed, are not in unlimited supply.

By the 1980s the herring had become scarce. Yet the tides that make the Clyde perilous for mariners also stir up nutrients, making it rich in biodiversity. So the fishermen turned to other species—saith, cod, plaice and sole—assisted by bigger engines and new dredgers. The Clyde fleet, based in Carradale, Girvan and other small ports along the Firth’s 100km stretch, could now fish deeper, for longer, and even in rocky places.

Politicians, who had once tried to husband the Clyde’s bounty, helped the slaughter. During the late 19th century trawling had been banned in most of the Clyde to combat the effects of overfishing. But later governments reversed that logic. As the trawlers fished out unprotected parts of the Clyde, they opened the protected parts. In 1984 the last serious protection, a ban on trawling within three nautical miles of the shore, was lifted by the courts. By the turn of the century there were scarcely any adult shoals left in the Clyde. These days, excluding a summer flush of mackerel, it is hard to find any big fish at all. Hugely reduced, the Clyde fleet now scrapes the seabed for scallops and prawns, a difficult enterprise that is destroying the habitat upon which hopes of regeneration depend. Only five small boats operate out of Carradale, employing a dozen men. “In just 20 years,” remarked an old fisherman in Girvan, “we knackered the Clyde.”

This is one of Britain’s biggest environmental disasters of recent times. But it is not widely known. Until 2010, when two marine biologists predicted, on the basis of historic catch data, that the Clyde was about to become Britain’s first “ecological desert”, it was scarcely mentioned in the national press. Even then the Clyde won no political champions—such as the 101 Conservative MPs who wrote to the prime minister last year to condemn unsightly wind turbines. Nor has the devastation sparked public protests such as those against hydraulic fracturing (or “fracking”, a technique for producing oil and gas) that forced an energy company called Cuadrilla to stop drilling in Sussex this month. Why?

Because the damage is underwater, and what the eye doesn’t see greens don’t often bleat about. That is why the global crisis of overfishing and marine pollution stirs less outrage than, say, the clearing of the rainforest. Yet the main reason is stupid politics.

Even Tory backbenchers cannot think the view-disturbing effect of a windmill as serious as the devastation of one of Britain’s most productive marine ecosystems. What passes for environmental protest over wind turbines is really NIMBY-ism on behalf of a few influential constituents. Nor, if they are serious, can greens maintain that fracking is a great evil. The technique has been used in oil and gas production for decades without causing the serious water pollution or earthquakes it is accused of. Environmental protest over fracking is really a fight over something else: either the greenhouse-gas emissions that all hydrocarbon production leads to, which is a legitimate worry, or the capitalist system that produces firms like Cuadrilla, which is not. These are illustrations of how dilettantish much of what passes for environmental protest truly is. The Clyde is a more tragic case.

The Clyde’s remote fisher folk—the hardy, easily romanticised agents of the Firth’s devastation—are a less attractive target for greens than energy firms. They are also a constituency local politicians do not wish to annoy. So no government or green has tried hard to stop the rapine. And the current Scottish government, run by the Scottish National Party, is especially reluctant. It has strong ties to the fishing industry, which is why, hoping to disprove the marine biologists’ claims, it commissioned a rival study of the fishery. Published last year, this judged the phrase “ecological desert” an overstatement; yet it agreed that there were hardly any fish in the Clyde worth catching. Amazingly, the fisheries minister, Richard Lochhead, suggested this vindicated his government’s support for the destructive scraping and dredging.

How to kill a culture

The trawlermen are formidable. Even as Carradale’s fleet shrank, and the mounds of fishing nets vanished from the harbour, they tended to rebut any suggestion that the Clyde was in trouble and they were the cause. This was, for decades, a truth rarely spoken in the village. Even now it is uttered mainly by old fishermen, made honest by the dying of a beloved industry.

Fishing, for as long as anyone can remember, was more than an occupation in Carradale. The community was founded on it. Youths went to sea in their uncles’ boats, formed ring-netting pairs with their neighbours, married one another’s sisters and celebrated by drinking and singing songs about herring. Support for the fishermen was bolstered by a desire to preserve these happy traditions. But how misguided that was. Carradale is shrinking. Its young folk are leaving; one of the five boats is crewed by Latvians for want of local labour. “Last year was a bad year, 18 deaths and the rest of us ageing,” was how an old fisherman greeted Bagehot on his return to the village. Few sing about herring these days. Nobody sings about prawns.

Article courtesy of the Economist.

Newlyn Fish Festival - Fishermens Mission Charity Auction 2013

Fishermens Mission Charity Auction 2013 from SWFishUk on Vimeo.

Photos and audio recorded at Newlyn Fish Festival 2013. The charity auction was in aid of the Fishermen's Mission and the Scouts UK.

The Fish Display was built by passionateaboutfish.co.uk - All the fish supplied was by local boats in Newlyn and caught over the weekend before organised by the CFPO cfpo.org.uk/

Courtesy of SWFish.

Nathan Outlaw - scores another success!

Book of the Year
and the winner is...............
............................................
..........................
..................
Nathan Outlaw!

Below is just one of the many award winning recipes personally tested by Through the Gaps!

Sourced from the cod ends of the inshore trawler Elisabeth Veronique, three lovely lemons, top sides scored and ready to go......

so,  you've obtained the fish and have guests to feed, what next?......

with the Great British Menu heading south west this evening here's a timely dip into Nathan Outlaw's superb British Seafood cook book - one of the first things noticed is the ample opportunity from within the pages to modify recipes by using the book as a mentor - in this instance, choosing a lemon sauce as a suggested accompaniment to the lemon soles..........

this mayonnaise type sauce is easily prepared with lemon juice, lemon zest and olly oil - and a little careful whisking.......

a handful of new Pentland Javelin spuds quickly dug up (the entire crop from a plastic builder's tub in the garden)......

washed and ready to go.......

as no clams were available this lemon sole recipe was used only as a guide to cooking just the fish.......

along with a handful of deep-fried courgette and other veg.......

then under the grill go the fish.......

with careful handling at serving time on the table, the bone frame is easily peeled away to leave just the fillets.......

lemons cooked on the bone are a great fish to present this way.......

the book is more than just a collection of the best British fish dishes, organised by fish type and at least two recipes for each, there are more really useful sections like the base recipes full of helpful hints and tips........

along with all the key preparation techniques explained in sufficient detail to give a novice the confidence to venture into preparing fish to inspiring those more accomplished home cooks who are keen to impress family and friends with an extended repertoire......

the step-by-step photos by David Loftus that accompany Nathan's clear instructions make this part of the book an invaluable guide to fish preparation in its own right.......

and the really helpful section on garnish and veg is there for that moment in time when putting together an impromptu meal or planning something more extravagant. 

Don't forget it's Fishstock Seafood and Music Festival this weekend in Brixham!

On Saturday 7th September 2013 the Fishmarket and Fish Quay of Brixham will be transformed into a musical and cookery spectacular!

Gates will open at 1000hrs with live music and cookery demonstrations starting from 1045hrs.

A host of bands, dancers and seafood cookery experts will keep you entertained right into the evening, with the last live act on the main stage finishing at midnight. Tickets A list of the music line up for the main stage and acoustic stage as well as the 'Castles Kitchens' cooking demonstrations, featuring live camera feeds and plasma screens on site for better viewing, can be found at the relevant links on this website.


Fans of cooking fish have two demonstration stages to choose from!

Castles Kitchen Stage One:

1045hrs: Opening the show: Fish Filleting by Award-winning Fishmongers Duncan and Sue Lucas who are “Passionate about Fish”.

1145hrs: Simon Hulstone Masterclass with Michelin Starred Executive Chef at the Elephant Torquay. 

1315hrs: Andy Sewell goes head to head against Richard Hunt in Battle of the Bays 

1430hrs: Mitch Tonks (Author, TV chef and proprietor Seahorse and Rockfish Dartmouth) takes the stage with David Jones (Manna from Devon Cookery School) in Ready Steady Cook. Mitch Tonks and his fishy friends in Brixham will be running a seafood BBQ during Fishstock. All proceeds to the Fishermen’s Mission. 

1545hrs: Richard Hunt and David Jones go head to head in Ready Steady Cook. 
1715hrs: Felicity Sylvester presents Lobster Hypnotising, seafood preparation and cookery. 

Castles Kitchen Stage Two:

10.45hrs: Felicity Sylvester will demonstrate Lobster Hypnotising, seafood preparation and cookery. 

1130hrs: Andy Sewell Masterclass with Head Chef at the Quayside Hotel Brixham 

1230hrs: David Galpin Materclass with Head Chef at Department of Hospitality South Devon College 

1330hrs: David Galpin, David Berry & David Wells (S D College) will perform and invite members of the public to participate in Seafood Preparation & Cooking 

Please note: David Galpin's team of chef tutors from South Devon College will lead classes of seafood preparation and cookery for local children from 1030hrs in the Yeovil College “Feast-Bus”.

@fishstock1

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