The IUCN/SSC Shark Specialist Group
Shark News 12: November 1998
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Commercial Landings of Sharks in
South-Western England
Philip Vas and Teresa Thorpe
Commercial fisheries can have a significant impact upon the status of
elasmobranch populations (Anon. 1997). Consequently it is important
that any fisheries which land such species, either as a directed catch
or as by-catch be strictly regulated. To regulate such fisheries, it is
important to have not only the biological data on which to build a
management plan, but also to maintain accurate species-specific
records of landings for monitoring purposes (NMFS 1997).
Unfortunately, in many parts of the world, this information is all too
frequently lacking.
The north-east Atlantic, FAO Fishery Area 27, contributes roughly
one-tenth of the world's total elasmobranch landings. One of the
major elasmobranch fishing countries in this region is the United
Kingdom, with average annual elasmobranch landings in excess of
25,000 tonnes/year, of which 67% are sharks (Bonfil 1994). The
principal shark species taken in the UK are the spurdog Squalus acanthias, lesser spotted dogfish Scyliorhinus canicula and the bull
huss Scyliorhinus stellaris. A number of other species are known to be
taken, but official figures currently fail to differentiate between them,
reporting them collectively under the heading of "dogfish".
Furthermore, these figures do not include details of by-catches or
discards and thus the true landings are likely to be somewhat higher.
In 1995 and 1996, recreational 'tag and release' shark fishing
tournaments were held in the Cornish city of Penzance in the far west
of England. During these tournaments, it was possible to conduct
some observations on elasmobranch landings at the nearby fishing
port of Newlyn, one of the most important and oldest ports in the UK.
From these initial observations, it was evident that a wide range of
elasmobranch species were taken and that different species were
susceptible to different gears. These preliminary observations formed
the basis for a more detailed and thorough survey of the fisheries at
Newlyn conducted between 1997 and
1998.
The Port of Newlyn and its Fisheries
Newlyn is situated one mile west of
Penzance and around seven miles east of
Lands End. Consequently, it is the most
western of the major ports in southern
England and has ready access to both
coastal and deeper, offshore waters of the
Celtic Sea and Bay of Biscay.
The port is home to a large fleet of
vessels ranging from 8 to 20 m in length
and between 11 and 40 GRT in weight.
The smaller vessels primarily work inshore
grounds, usually either trawling or
crabbing, with some occasionally fishing
using longlines. These vessels operate on a
daily basis, returning to port to land catches
at night.
The larger vessels are either gill netters
which target hake Merluccius merluccius
and monkfish Lophius piscatorius, orbeam
trawlers targeting a wide variety of flatfish and shellfish. One or
two of the larger vessels occasionally fish using demersal longlines
set for conger eels Conger conger. These larger vessels operate
further offshore on extended trips of five to seven days, occasionally
as far out as the Bay of Biscay. During the summer months, several of
the vessels specifically switch to driftnets in order to work the
profitable tuna grounds in the Bay of Biscay, with trips lasting around
15 days.
The port of Newlyn is also important in that it is a major fish
market, receiving landings by road from as far afield as Newquay,
Padstow and many of the smaller Cornish fishing villages for sale.
Thus, observations of landings made here are truly representative of
those for the whole south-west of England.
Detailed Shark Landings
All of the fisheries were observed to land sharks at one time or another
during the study period. Those that landed sharks as a by-catch were
considered to be 'incidental fisheries', while those targeting sharks
were considered 'directed fisheries'.
A total of 11 different species of shark were recorded during both
the preliminary observations and study period. Spurdog and catsharks
(Scyliorhinus spp.) were the most abundant of all sharks taken and
were present in landings throughout the year. Spurdog were usually
taken in association with gill nets or bottom-set longlines and were
considered a targeted species by some vessels. In contrast, the
catsharks were taken closer inshore, usually by trawlers, and were
considered a by-catch. Few catsharks were sold on the market for
human consumption, with the majority (90% of those observed)
being sold for bait to commercial crab fishermen. As the landings of
spurdog and catshark are recorded by the Ministry of Agriculture,
Food and Fisheries in the UK, little else will be said of their landings
at this point.
Of the remaining species, blue shark Prionace glauca, tope
Galeorhinus galeus and porbeagle Lamna nasus were the most
abundant. Three species were represented by single specimens in the
catches: two from tuna vessels, the bigeye thresher Alopias
superciliosus and the kitefin shark Dalatias licha, while the starry
smoothhound Mustelus asterias was taken in a gill net. One species,
the sixgill shark Hexanchus griseus, was
found to be surprisingly abundant in the
landings, appearing regularly in gill net
catches during the late summer and
autumn.
Inshore Shark Landings
Blue Sharks
Of the larger sharks, the blue shark was the
most commonly landed species, being
taken on a variety of gears. Some were
taken on bottom set longlines with some
individuals taking the baits on the way
down, others while the gear was set in 40-
50 m of water. A small proportion were
caught in gill nets, set close to the bottom
in 50-70 m of water. In both instances,
these sharks were considered a by-catch.
The greatest proportion of blue shark
(excluding tuna catches) were taken on lines
set specifically for the sharks. Off the Cornish
coast, it is common practice for fishermen to
set lines attached to the dahns on the ends of
thenets. These lines support 5-8 hooks, each
baited with squid, and are designed to catch the blue sharks which are
locally abundant between May and October. The blue sharks, although
targeted with these hooks, do not form the principal catch of the fishery (which is the hake, taken in the nets), but are regarded
by the fishermen as a bonus catch. Thus the sharks
represent an 'accessory catch' to the net fishery.
A total of 796 blue sharks were observed,
86% of which were females. Males ranged in
length from 72 to 214 cm TL while females
were from 88 to 251 cm TL. The average size
of male sharks was always less than that of
females.
Landings of sharks were made as early as
June and, rather surprisingly, as late as December
when a group of very small females 88-130
cm TL were caught. No blue sharks were caught in
November, during a period of bad weather which
restricted fishing. Sixty-seven percent of all blue sharks
caught were taken in July and August 1997.
Porbeagle Sharks
Porbeagle sharks were landed on a regular basis, with all being
landed as a by-catch from gill nets. None were taken on longlines.
A total of 31 porbeagles were observed although a number of others
were landed when no observer was at the market. Males and females
occurred in roughly equal proportions (15 males, 16 females),
though again males were slightly smaller (71-210cm TL) than
females (101-244cm TL).
No evidence of seasonal abundance was apparent in the landings,
with roughly equal numbers being taken in all months. Unlike the
blue sharks which are gutted at sea and fetch a low price at the
market ($0.50\lb), the porbeagles were highly prized, landed ungutted and sold for a much higher price (up to $2-3/lb) at auction. Many were exported to France after sale.
Tope Sharks
A total of 59 tope were landed during the study. All were taken in gill nets
set in at least 60 m of water and were landed in an ungutted condition.
While examining boxes in the market, several tope were found mixed
in with spurdogs and so were not readily visible. Whether they had been
recorded separately by the skippers or Ministry of Agriculture, Food and
Fisheries (MAFF) officers is not known. The observers themselves may
have missed some individuals as several landings of spurdog could not
be checked. Consequently, it is likely that the figures for tope are an
underestimate of those actually caught.
Of the tope observed, 59% were males ranging in length from
44 to 148 cm TL, while the females ranged from 81 to 157 cm TL,
with an overall larger average size. There was a noticeable seasonal
change in the sex ratio of the landings, with males becoming more
abundant than females later in the year.
Six-gill Sharks
This species was rarely landed as it has no effective market value.
Consequently, those taken as a by-catch in gill nets were usually
discarded at sea. However, once the fishermen knew that the
observers were interested, records were kept of numbers caught.
During the study, a total of 123 records were provided. Of those that
were returned to market (primarily for the observers interest), all
were females ranging length from 78 to 161 cm TL. Catches of this
species were more common in the western approaches and there
was some suggestion of localised abundance, with skippers catching
either isolated specimens or large hauls (up to 60 sharks).
Offshore Tuna Landings
During the months of July and August each year, up to five of the
larger vessels (18 m in length), changed from gill nets to drift nets
and prosecuted the tuna fishery in the Bay of Biscay (40-51°N,
10-15°W). Fishing for 8-10 days with nets of 2.5 km, these vessels
took large by-catches of sharks, primarily blue
shark. As these sharks were not the targeted
species and took up valuable space in the
hold, many were discarded. An on-board
observer programme in 1995 indicated a
discard rate for blue sharks in this fishery of
37% (Tregenza 1995).
A total of 588 blue sharks were landed
from five tuna trips observed. Individual
catches ranged from 96 to 180 sharks with
the number varying depending on the quality
of the tuna fishing. Generally more sharks were
landed when tuna were scarce. Males ranged in
length from 115 to 253 cm TL and accounted for
46% of the landings but were generally smaller than
the females (105-222 cm TL). There was a slight
variation in sex ratio of the catches between vessels, attributed to
geographical differences in fishing locality.
Two other species of shark were regularly (i.e in more than one
trip) taken as a by-catch, the porbeagle and shortfin mako Isurus
oxyrinchus. Unlike the blue sharks, because of their high market
value, 100% of these species were retained. In 1997, three makos
were observed (two males and one female, 117-172 cm TL). Higher
numbers are known to have occurred in previous years. For porbeagle
shark, a total of 12 specimens were observed (seven males 88-217cm
TL, five females 102-212 cm TL).
From these data it is clear that the blue shark represents the
principal elasmobranch by-catch from this fishery. However, the
British vessels represent only a relatively small proportion of the effort
expended in the tuna fishery. Larger numbers of Spanish and French
vessels also prosecute this fishery, previous studies indicating total
by-catches of blue sharks in excess of 82,000 sharks in 1993.
The study has extended our knowledge of the regional biology of
various shark species and has also thrown up several new problems.
For example, why do commercial fisheries catch male blue sharks
while recreational fisheries in the same waters do not? It has also
shown that blue sharks may remain longer in British coastal waters
than was thought. Previous studies suggested few if any sharks,
remained as late as October. And finally, the study has shown that the
six-gill shark is comparatively abundant and the area may provide an
opportunity for an extended study of this species.
This study has demonstrated the relative susceptibility of sharks to
fisheries in the NE Atlantic and given some indications of which areas
need consideration. It is clear that drift net fisheries produce the
highest mortality upon shark populations in this region. Monitoring of
these fisheries will continue through 1998-1999, but additional
studies will focus on technical methods of reducing the by-catch from
such fisheries.
References
Anon. 1997. An Overview of the impacts on the biological status of sharks.
Discussion Paper Pursuant to CITES Resolution CONF. 9.17.
Bonfil, R. 1994. Overview of world elasmobranch fisheries. FAO Fisheries
Technical Paper 341.
National Marine Fisheries Service 1997. Managing the Nation's Bycatch:
Priorities, Programs and actions for the National Marine Fisheries Service.
US Dept of Commerce, Washington DC, March 20, 1997.
Tregenza, N. 1995. Cetacean bycatch in the UK tuna driftnet fishery in 1995.
Contract Report to the Ministry of Agriculture, Fisheries and Food. P639.2/
11,95. Science & Environment Section. House of Commons Library.
A more detailed account of this study is in preparation: Commercial
and recreational landings of sharks in SW England, Aquatic
Conservation.
Philip Vas, c/o 15 Woodlands Ave,
Peel Green, Eccles,
Manchester, M30 7GN, UK
Email: 106370.1164@compuserve.com
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