The IUCN/SSC Shark Specialist Group
Shark News 4: July 1995
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Risk-prone management of the
US Atlantic shark fishery
Merry Camhi, National Audubon Society
Introduction
It is widely accepted that sharks are highly vulnerable to overfishing
because of their K-selected life history strategies. Indeed, shark
fishery failure is the rule rather than the exception, and it has been
estimated that nearly 90% of the shark fisheries in the 20th century
have failed because of a lack of aggressive management once shark
populations begin to decline (Compagno and Cook, in press). The
United States is one of only three major shark-fishing nations that
actively manage their shark fisheries (Australia and New Zealand are
the others)(Bonfil 1994). In April 1993, after five years in development,
the US National Marine Fisheries Service (NMFS) finally implemented
the Fishery Management Plan for Sharks of the Atlantic Ocean
(NOAA, 1993). In this plan NMFS has proclaimed that "sharks must
be managed very conservatively". However, the current quotas and
slowness to implement other conservation measures recommended by
its own scientific experts suggest that NMFS has adopted a risk-prone
agenda for shark management in the Atlantic, Gulf of Mexico, and
Caribbean Sea.
A brief history
Commercial fishing for Atlantic sharks in the US began in the 1930s,
and landings were relatively low (less than 2,000 mt) prior to 1986
(see graph below). By the mid-1980s, the popularity of shark meat
had increased and the skyrocketing demand for shark fin soup in Asia
led to rapid expansion of the Atlantic commercial shark fishery. At
that time, NMFS was actively encouraging longliners from the over-
capitalised tuna and swordfish fisheries to switch over to sharks,
despite lack of an adequate assessment, data collection programme,
or management plan. As landings grew to a peak of 7,122 mt in 1989
(NOAA 1993), so did concern over the status of previously abundant
sharks. Many historical shark angling tournaments were abandoned
because of declining catch rates. A fishery management plan (FMP)
was finally drafted in 1989, but implementation was delayed until
1993 mainly because of uncertainty in estimating maximum
sustainable yield (MSY) and overfishing (Hoff 1990). Unfortunately,
this reluctance to take precautionary measures in the face of
scientific uncertainty has become the operational
mode of NMFS shark management.
Landings of shark on the US Atlantic coast
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Although the FMP needs much improvement,
a number of beneficial conservation provisions
were built into the plan. The FMP grouped 39
shark species in the management unit into three
categories because species-specific data were
lacking: large coastal sharks (22 species), small
coastal sharks (7 species), and pelagic sharks (10
species). Although spiny Squalus acanthias and
smooth Mustelus canis dogfish are taken in large
numbers in directed fisheries they are not
included in the management unit. Quotas were
established for the large coastal and pelagic
categories, and recreational bag limits were also
implemented as an important first step toward
reducing fishing pressure. Trip limits for large
coastals (4,000 lbs) were imposed as well in
1994.
To improve management and data collection,
commercial shark fishers must now obtain
permits. Less than 200 of the 1,631 permit
holders actively fish for sharks. NMFS is
considering limiting access to reduce over-
capitalisation in the fishery (M. Bailey, pers.
comm.). Mandatory dealer reporting has been
recently implemented. In an effort to discourage finning, the FMP
prohibits landing only the fins and discarding the carcass. Yet this
approach has not worked to reduce shark mortalities because the
export of fins from sharks that are landed is still the driving force
behind the fishery.
Photo: Page Chichester, Audubon Productions © 1990.
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Risk-prone management
Almost all indicators suggest that Atlantic shark populations, especially
those in the large coastal category, are in trouble. Total fishing
mortality has greatly exceeded the MSY every year since 1979 (Hoff
1990). In 1994, NMFS convened a Shark Evaluation Workshop (SEW)
(NOAA, 1994) composed of NMFS scientists and outside scientific
experts to undertake a new stock assessment. The SEW confirmed that
by 1986 the abundance of many of the large coastal species may have
already declined by 50-75% from the 1970s levels. Ongoing declines
in catch per unit effort estimates, average weight, and species
richness all suggest that the large coastal assemblage is still declining (NOAA, 1994).
The FMP is considered by many scientists to be overly optimistic
in its estimation of sustainable yields and recovery times (Burgess,
1995). To wit, NMFS used the period of maximum production (1986
to 1991 landings) as a biological reference and assumed that "any
annual production, including the maximum, is sustainable." More
reasonable and precautionary estimates of MSY would have been
based on the entire data set from 1979, since many species had
already undergone serious decline by 1986. In addition, although
data on by-catch are notoriously incomplete, the FMP estimates that
annual discards between 1979 and 1988 averaged 16,000 mt. This
suggests that incidental catch of sharks in the swordfish, tuna, and
shrimp fisheries exceeds the directed catch (Hoff, 1990). Yet it is not
clear how this discard mortality is incorporated into the estimates of
MSY, and little has been done to date to reduce the incidental catch
of sharks on pelagic longlines or in gillnets.
NMFS has legitimately argued that an incomplete and
inconclusive data base has hindered effective management. But so
has NMFS's use of unrealistic life history traits in the FMP's
population model. For example, the model relies on an annual
replacement rate of 26%, which is 2 to 10 times higher than is
biologically realistic even for the fastest-growing species in the large
coastal group (Musick 1994). Sandbar sharks Carcharinus plumbeus,
which comprise almost 80% of the large coastal landings, have an
intrinsic rate of increase of from 2% to 12% depending on the age of
sexual maturity, fertility, and longevity modelled (Musick, 1994;
Hoff, 1990). Estimates of survivorship employed in the FMP model
(0.97 for sandbar sharks) are also unreasonably high (Hoff, 1990;
Manire and Gruber, 1993). These erroneous assumptions led NMFS
to predict a two-year recovery for the overfished large coastal species
in the FMP (which was rejected outright by the SEW in 1994).
Yet almost all evidence on depleted shark populations suggests
how wildly unrealistic a 2- to 6-year recovery is for these slow-
growing creatures. The devastated porbeagle Lamna nasus fishery in
the North Atlantic in the 1960s is just one example. When this fishery
collapsed (after only 6 years), the population could not have been in
much worse condition than some of the species that are currently
managed under the FMP. The relatively fast-growing porbeagle
should be more resilient to over-fishing than such slow-growing
species as the sandbar shark. Yet the porbeagle has still not recovered
even 30 years after commercial fishing essentially stopped. The Shark
Evaluation Workshop advised NMFS that recovery of shark populations
to 1970s level could take decades because of the low reproductive
potential of most species. NMFS, however, seems content to 'recover'
sharks to their already depleted 1986 levels.
Reversing the trends
Have the management measures instituted by NMFS, such as quotas
and bag limits, been effective in reversing the decline of Atlantic shark
populations? NMFS and the Shark Evaluation Workshop argue that it
is too soon to tell. But the 1995 stock assessment (NOAA, 1995),
based on 31 catch per unit effort time series, confirmed the warning
of the 1994 SEW that "any total allowable catch might be considered
risk prone" (SEW, 1994). In response, NMFS wisely agreed to
cancel a previously scheduled quota increase for 1995. But
because off laws in the population model, many scientists, fishers,
and conservationists have argued that the current quotas for large
coastal sharks are still too high to permit recovery. Precautionary
recommendations have ranged from reducing the current quota by
30% to a complete closure of the large coastal fishery until clear signs
of recovery are evident.
Beyond reducing annual fishing mortality, the closure of nursery
grounds during the pupping season was the single most important
measure recommended by the 1994 SEW, The NMFS has not proposed
action on nursery protection, although discussions are under way (M.
Bailey, pers. comm.).
Small coastal sharks are subjected to high, but under-reported by-
catch mortality in the Gulf of Mexico (Burgess, 1994). The NMFS has
acknowledged that "declining catch per unit effort and life history
characteristics indicating low productivity for pelagics and small
coastals also suggest that a prudent approach is warranted for these
groups." Still NMFS has failed to institute a quota for small coastals,
to lower the large pelagics quota, or to address by-catch problems, all
on the grounds of insufficient data.
For a shark fishery to be sustainable, management must be based
on the biological constraints of the fish rather than driven by the short-
term economic interests of the fishery. The NMFS repeatedly
acknowledges the vulnerable nature of shark fisheries, yet continues
to favour risk-prone policies while invoking scientific uncertainty as
an excuse to avoid making tough management decisions, it may be
many years before we have the kind of data we need to build robust
population models or defensible estimates of MSY. In the meantime,
given the life history traits of sharks, common sense alone argues for
a more risk-averse management regime. We only need to look to the
collapse of the New England groundfishery - or practically any shark
fishery worldwide - to see the consequences of foot-dragging and
reactive management.
Literature cited
Bonfil, R. 1994. Overview of world elasmobranch fisheries. FAO
Fish. Tech. Paper 341, FAO Rome. 119 pp.
Burgess, G.H. 1995. Status of shark populations in the western North
Atlantic. In: Global Shark Action Plan. IUCN Shark Specialist
Group. In preparation.
Cook, S.F., and L.J.V.Campagno. 1995. The failure of shark fisheries:
implications for management in southern Africa. In preparation.
Hoff, T.B. 1990. Conservation and management of the western North
Atlantic shark resource based on the life history strategy limitations
of sandbar sharks. Ph.D. Diss., Univ. Delaware, Newark, DE.
282pp.
Hoff, T.B., and J.A. Musick. 1990. Western North Atlantic shark-
fishery management problems and informational requirements.
In: Elasmobranchs as living resources: advances in biology,
ecology, systematics, and the status of the fisheries. (H.L. Pratt Jr.,
S.H. Gruber, and T. Taniuchi, eds.), pp. 455-472. U.S. Dept.
Comm., NOAA Tech. Rep. NMFS 90.
Manire, C.A., and S.H. Gruber. 1993. A preliminary estimate of
natural mortality of age-0 lemon sharks, Negaprion brevirostris.
In: Conservation biology of elasmobranchs (S. Branstetter, ed.),
pp. 65-71. U.S. Dept. Comm, NOAA Tech. Rep. NMFS 115.
Musick, J.A. 1994. Comments on proposed modifications of the
fisheries management plan for sharks of the Atlantic Ocean.
Submitted to NMFS Nov. 17, 1994.
NOAA. 1993. Fishery management plan for sharks of the Atlantic
Ocean. NOAA, NMFS, U.S. Dept. Comm. Feb. 25, 1993.
NOAA. 1994, Report of the shark evaluation workshop, March 14-
18, 1994. NOAA, NMFS. U.S. Dept. Comm. 47 pp.
NOAA. 1995. 1995 Shark evaluation annual report. NOAA,
NMFS. U.S. Dept. Commerce. 23 pp.
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