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Spurdog

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Spurdog by Marc Dando

Description

Also known as spiny dogfish, rock salmon or flake the spurdog is a small grey shark with spines at the base of each dorsal fin. They grow to a maximum size of 124 cm.

Sustainability Overview

Spurdog is a long-lived, slow-growing, and late-maturing species and therefore particularly vulnerable to fishing mortality. The North East Atlantic stock has been heavily depleted over the past 50 years but thanks to recent management measures is now showing some signs of recovery. Targeted fisheries for the species have effectively been outlawed as there is Zero TAC (total allowable catch). Bycatch in non-target fisheries still occasionally occurs as it is difficult to predict where groups of spurdogs will occur. Since 2016 Cornish vessels have been working on a project with CEFAS, the Spurdog Bycactch Mitigation Scheme , which provides real time data from fishermen on spurdog catches to enable other fishers to avoid accendentally catching this species. The species is assessed as Vulnerable globally by IUCN and in 2010 was added to the OSPAR list of threatened and/or declining species and habitats.

50 tonnes of spurdog were landed to Cornish ports legally in 2019, with a value of £94k (MMO data).

Updated December 2020

Sustainability ratings for this species

All Applicable Methods

Avoid eating Spurdog, often marketed as rock salmon, or flake, regardles of the method of capture.

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How we rate fish

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.

Biology

Spurdogs are a highly migratory species that is capable of moving great distances in very little time. They grow slowly and have a low rate of reproduction meaning that this species is very vulnerable to fishing. Biological vulnerability rating is high 69%, Cheung et al 2005. Spurdog (spiny dogfish, dogfish, rock salmon or flake) are sharks. In the North Atlantic female dogfish grow to a maximum total length of 110-124cm, males 83-100cm. In the Northwest Atlantic spurdog mature at around 60cms total length and at an age of 6 years for males and at around 75cms, at an age of 12 years for females. In the Northeast Atlantic females are reported to mature slightly larger and older at 83cm total length and 15 years. Gestation or pregnancy lasts between 18 and 22 months, one of the longest recorded for any vertebrate, and they give birth to live young. The fecundity of spurdog increases with length, and females of 100-120cm produce a higher number of pups (10-21) than those females below this length. Spurdog tend to aggregate in groups of one sex and size.

Stock Info

As the most commercially valuable shark species caught in European waters spurdogs have been fished at high levels for the last 40 years and stocks are thought  to have decreased by over 90% since the 1970’s in European waters (ICUN). The species is assessed as Vulnerable globally  by IUCN and in 2010 was added to the OSPAR list of threatened and/or declining species and habitats.

ICES say that Spurdog stocks suffered a high fishing mortality for more than four decades, and was not managed during this time. Management measures have been restrictive only since 2007. The spawning biomass and recruitment have declined substantially since the 1960's and are now stable at a low level. Exploitation is now below MSY level which is good and populations are showing signs of slight recovery which is very encouraging but stocks are not yet above safe levels.

Spurdogs  have tough skin which means that they have a higher survivability when accidentally caught and released back into the sea by fishermen, providing they haven’t drowned from lack of oxygen. 

ICES latest advice is unchanged - although fishing pressure is below sustinable levles stocks overall (despite patchyness) are depleted below MSY, and they advice zero catch in 2021. 

 

Management

It is currently illegal to land spurdogs commercially, a Zero Total Allowable Catch has been set in European Waters since 2010. As spurdogs are patchy in their distribution when fishermen accidentally catch spurdogs they will usually catch large numbers. The Spurdog by-catch avoidance project  (CEFAS, Sharktrust  and Cornish Fish Producers Organisation) has given permission to 10 participating vessels to land spurdogs (2 tonnes per boat per month), which have died in fishing gear, as long as accurate catch and discard records are kept. Real time infomation is then collated and used to inform other fishers of areas where there is more of a chance of accidentally catching spurdogs. 

Capture Info

Spurdogs have been targeted in the past using nets and longlines but are now cannot be targeted but are occasionally caught accidentally in gill nets, trawls and with longlines. Any caught currently have to be discarded as they are not allowed to be landed, except for those vessels working in the spurdog by catch avoidance project with CEFAS.  In 2019 50 tonnnes of spurdog were landed to Cornish ports (MMO) data. Fishermen say that it is very frustrating when they accidentally catch spurdogs as they damage gear and very large quantities are caught. It is reportedly very hard to avoid catching them despite sharing infomation with other skippers as the movement of schools is random. 

References

IUCN Red list Spiny dogfish 2020
ICES advice 2020 Spurdogs
Project Neptune final Report CEFAS 2016
ICES advice October 2018 Spurdogs 
Spurdog by-catch avoidance Programme 
 
MMO landings data
 
Shark Trust; 2010. An Illustrated Compendium of Sharks, Skates, Rays and Chimaera. Chapter 1: The British Isles and Northeast Atlantic. Part 2: Sharks. 
OSPAR Commission 2010, Background information for spurdog or spiny dogfish, biodiversity series 2010
MB0125: Common Fisheries Policy reform implementation: aligning zero quota species and improving fisheries management – a spurdog case study. DEFRA
 
Fordham, S., Fowler, S.L., Coelho, R., Goldman, K.J. & Francis, M. 2006. Squalus acanthias. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 28 January 2015.
 

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