John Dory

Zeus faber

John Dory

Image | Illustration by Sarah McCartney Copywrite Cornwall Wildlife Trust

Description

A strange looking, but delicious fish that is common around the Cornish coast. A John Dory's bizarre shape and long fins make it look from another planet.  It has a large mouth which is used to suck in very large prey items such as fish and shrimps. It has a black spot on each side of the body which is said to be the thumb print of St Peter. It has a fantastic scientific name being named after Zeus, king of the Greek Gods.


Sustainability Overview

John dory is a relatively abundant species in Cornish waters that is caught as a valuable by-catch in trawl and net fisheries. Little is known about stocks of john dory but there is no evidence that numbers are decreasing, however they are a species which has a relatively high vulnerability to fishing. Due to their strange shape young John Dory are easily caught in fishing gear and they can't easily escape thorugh mesh or escape gaps. Avoid eating small John Dory smaller than 29cm that haven't had the opportunity to spawn yet.

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When is best to eat?

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Gill Netting

Cornish vessels landing to Cornish ports

Gill nets are lightweight nets made of nylon (monofilament) fishing line that are anchored to the seabed and are used to catch fish by entangling the gills.

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Demersal Trawl

Cornish vessels landing to Cornish ports

Demersal trawls are large nets that are pulled through the water with the bottom edge of the net touching the seabed. At each edge the net is pulled open by metal ‘trawl doors’. Sometimes referred to as Otter trawling.

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Beam Trawling

Cornish vessels landing to Cornish ports

Beam trawls are nets attached to a steel beam that holds the net open. The belly of the net is made of chains and the upper surface of the net is mesh. Beam trawlers pull two nets along the seabed simultaneously.

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How we rate fish

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Cornwall Good Seafood Guide rates fish on sustainability using a scale of 1 to 5.

1, 2 and 3 are recommended, Fish to avoid are rated 5.

We use the system devised by the Marine Conservation Society (MCS) so our scores are comparable with the scores produced by MCS for the UK and fisheries from all around the world. For more information on scoring click here.

Sustainability Overview

John dory is a relatively abundant species in Cornish waters that is caught as a valuable by-catch in trawl and net fisheries. Little is known about stocks of john dory but there is no evidence that numbers are decreasing, however they are a species which has a relatively high vulnerability to fishing. Due to their strange shape young John Dory are easily caught in fishing gear and they can't easily escape thorugh mesh or escape gaps. Avoid eating small John Dory smaller than 29cm that haven't had the opportunity to spawn yet.

John Dory

Biology

John Dory is an ambush predator that relies on its thin front profile to creep up on smaller fish. Once close it launches an attack by rapidly opening its huge mouth, creating a vacuum that sucks in its unsuspecting prey. John Dories usually live a solitary life but are occasionally found in small schools in inshore waters. They become sexually mature at an age of around 4 years and at a length of 29-35cm. 
Reproduction takes place at the end of winter and at the start of spring in the north eastern Atlantic, (ICES WGNEW report 2010). Vulnerability to fishing is relatively high 68% (Cheung et al 2005).
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Stock Info

Landings of John Dory have decreased from around 100 tonnes per year in 2000 to around 70 tonnes per year in recent years.
John Dory is considered an under-utilised species. Ref CEFAS 2011. Under-utilised species are ones that fishermen don't catch their full quota of; or they catch them but then discard the fish because no one wants to buy them. CEFAS have compiled a list of these species using quota and discard information, expert advice and local knowledge and chose around 50 under-utilised species to study. To determine their sensitivity to over-fishing CEFAS has developed a system, the Relative Life History Sensitivity Analysis, to study the risk. It uses biological information like growth and breeding strategies to see how increased fishing pressure might damage each species. They then ranked the species by how tolerant they are to being over-fished. 
From Project inshore – Catch Per Unit Effort indices show an increase in biomass and abundance since the late 1990s up to 2008, and a drop in 2009. The fishery independent surveys indicate four strong year classes in 1997, 2001, 2004 and 2007, and therefore it is unlikely that recruitment is impaired (SG60+). However, it is not possible to be sure that recruitment has not been affected by the fishery (SG80a-) and no target region has been defined (SG80b-).
An ICES working group (WGNEW) brought the most recent European information on John dory together in 2010. Research vessel data shows an increasing trend in abundance in most European waters from the late 1990s to 2009 when a decrease was observed. This is as a consequence of good recruitment of young fish into the population during  warm years 2001, 2004, and particularly 2007.
It was not possible to run analytical assessment models on these data; so these survey results have to be regarded as indicative trends. 
There is also some evidence that the abundances of warm-water fish species (such as John dory) have increased in UK waters during recent decades due to climate change, while many cold-water species have experienced declines.
 

Management

John Dory catches are not limited by quota. There is also no Minimum Landing size. 
According to Project inshore, there is a disincentive for the IFCA to take management action within the 6 mile limit and similarly for MMO to take management action outside of 0-6nm as this would only apply to local or UK vessels, not foreign vessels, therefore would be seen as unfair. 
 

Capture Info

John dory are caught in Cornish waters by gill nets and in demersal and beam trawls.

References

Seafish Responsible Sourcing Guide John Dory January 2014 v3
MMO landings data Cornwall
ICES WGNEW report 2010
Identifying underutilised species - Tom Catchpole, Cefas, January 2011
Cheung, W.W.L., T.J. Pitcher and D. Pauly, 2005. A fuzzy logic expert system to estimate intrinsic extinction vulnerabilities of marine fishes to fishing. Biol. Conserv. 124:97-111
 

Recipes for John Dory

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