Download Coastal Conservation Offsets Mortality at Sea: Applying the Bycatch

COASTAL CONSERVATION OFFSETS MORTALITY AT SEA:
APPLYING THE BYCATCH MITIGATION MODEL
CLAIRE M. FIESELER1
I. INTRODUCTION
U.S. fisheries are successfully reducing bycatch rates, but management strategies are
reaching diminishing returns. New bait methods and fishing gear modifications have enabled the
Hawaiian longline tuna fishery to reduce seabird bycatch by 67% since 2001 (Gilman,
Kobayashi et al. 2008). Despite its strict bycatch program, the fishery’s reduction “success” is
relative. The catch of non-target species is practically unavoidable in commercial fishing.
Gear innovation and modification reaches a certain limit of effectiveness and
eventually shows diminishing returns. In other words, for each additional dollar invested in gear
modification, the additional poundage of bycatch avoided becomes smaller. Marine biodiversity
continues to be threatened by industry at sea; yet, conservation schemes on shore may now offer
an innovative solution. A new model proposes a bycatch mitigation program for seabirds by
addressing mortality sources in their coastal habitats. If successful, this paper contends that the
model may be applicable for other species, like ontogenetic reef fish.
II. COMPENSATORY MITIGATION FOR BYCATCH: THE MODEL
Invasive feral cats and rats have decimated island-breeding populations of albatross
and shearwater seabirds. Wilcox and Donlan (2007) highlight cases in Mexico and the South
Pacific where predation leads to levels of population mortality comparable to that of nearisland
bycatch. This analysis was the first to propose a bycatch mitigation program that accounts for
more than one stage of a seabird’s life cycle. In short, the dangers a species encounters while
foraging at sea may be mitigated by conservation strategies targeted for its coastal life stages (ie.
nesting chick, breeding adult).
Wilcox and Donlan (2007) introduced the idea of compensatory mitigation as a marketinfluenced approach to fishery-conservation conflicts. Their proposed program involves “levying
fishers for their bycatch and using the funds to remove invasive predatory mammals from
breeding islands [used by endangered seabirds].” The positive impact of predator removal should
not be understated. The analysis illustrates that 45% of seabirds explicitly threatened by fishery
bycatch are concurrently threatened by invasive species on their breeding grounds (Figures 2,
(Wilcox and Donlan 2007).
From an economic perspective, the model maximizes the “bang” per conservation
1
Claire Fieseler is a first year graduate student at the Nicholas School of Environment and Earth Sciences at Duke
University in Chapel Hill, North Carolina, where she studies environmental management. She can be reached at
[email protected].
buck. It has been difficult for even the best managed fisheries to avoid high levels of nontarget
species mortality. New Zealand’s squid fishery and Hawaii’s pelagic longline fishery –
generating $122 and $50 million a year, respectively - closed early in the 2005 season due to
bycatch of endangered species (Wilcox and Donlan 2007). Clearly, regulatory intervention come
at high costs. Compensatory mitigation can be cheaper and may help avoid this type of
demographic crisis within populations.
To test the cost-effective potential for a bycatch mitigation scheme, Wilcox and
Donlan (2007) modeled the endangered flesh-footed shearwater as a trial species. The entire
Australasian population breeds on rat-ridden Lord Howe Island (AU) and serves as an
appropriate case study: “Closure [of fishing] in 750-km radius around… the island results in a
6% increase in shearwater population, with an economic cost of $3 million. Eradication of rats,
costing approximately US$500,000, results in a 32% increase, making such an action 23 times
more effective than fishery closure from a one-year conservation return-on-investment
perspective.” In the long term, eradication results in 64% increase in annual population growth,
while fishery close yields a 63% increase. Since eradication is much less expensive, it still
suggests more “bang” for the theoretical buck.
III. APPLYING THE MODEL
At the moment, this mitigation strategy is indeed simply theoretical – highly innovative with
many unknowns. For example, Wilcox and Donlan (2007) state that “individual vessel levies be
set at the cost of offsetting the bycatch [it] takes.” With adequate fee levels and vessel
accountability, the strategy could create incentives for fishers to avoid bycatch. But the political
feasibility of such a levy is uncertain. It seems likely that smallbusiness fishers, with less
capacity to modify gear, would suffer the most economically under such a levy. Meanwhile, it
has been statistically proven that the biggest culprits of “gross bycatch” are large-scale fishing
ventures, regardless if “bycatch-friendly” technology is employed (Lewison, Crowder et al.
2004).
From the terrestrial approach, it would be more politically feasible to eradicate troublesome
invasive species. 400 islands worldwide has been eradicated of at least one invasive mammal
species (Howald, Galvan et al. 2007). The ecological context of each site, however, must be
closely studied. Eradication is only effective where endemic species are not likely to reclaim the
predatory niche left by the removed species. Eradication would not present the enforcement
problems of current conservation regulations, like “bycatchfriendly” baiting methods. It is
imperative, however, that sufficient funding from levies be funneled toward monitoring the
eradicated breeding sites.
IV. BEYOND SEABIRD SPECIES
The Wilcox and Donlan (2007) approach is truly innovative. No other study has proposed a
bycatch program rooted in the notion of offsetting other mortality sources of species that shift
habitat. Marine species have dynamic life cycles, often characterized with temporal or
ontogenetic shifts in terrestrial, aquatic, and marine habitat. While the Wilcox and Donlan (2007)
study limits its analysis to seabirds, its habitat-based framework suggests that other bycatch
species could benefit from this type of approach.
Snappers and groupers are keystone species in the coral reef ecosystem;
unfortunately, they are becoming over-exploited by industrial fisheries (Gobert, Berthou et al.
2005). The market value for these species has risen significantly in the past decade.
Consequently, traditional handlines and spearguns are being replaced by less selective industrial
gear and increased fishing effort across the Gulf of Mexico. The losers of this industrial growth
have been non-market reef fish. Most Caribbean reef fish are ontogenetic habitat-shifting species
whose populations are threatened by concurrent habitat destruction: coral cover is decreasing due
to coral bleaching, while mangroves are being destroyed for coastal development. The additional
pressure of bycatch rates make certain fish species susceptible to regional extinction, like the
highly threatened parrotfish (Rotjan and Lewis
2006).
Mangroves provide a vital nursery grounds for both the parrotfish and the snapper/grouper
families. For example, the gray snapper (Lutjanus griseus) exclusively inhabits mangroves for
approximately two years before reaching adulthood in southeastern Florida; juvenile parrotfish
may feed in mangroves for three year before recruiting to reef systems (Faunce and Serafy 2008;
Rotjan and Lewis 2006). If bycatch mitigation levies can be feasibly managed in the Gulf region,
funds may be funneled toward the conservation of continuous mangrove stands. New research
has been successful in quantifying the high economic value of mangroves to fisheries (AburtoOropeza, Ezcurra et al. 2007). Thus, further incentive exists for snapper/grouper fisheries to
prevent mangrove destruction to offset their impacts.
V. CONCLUSION
Financing the reduction of bycatch mortality provides an optimization problem. To compensate
for trends in diminishing returns, perhaps managers should avoid single-factor solutions, such as
gear modification. “Ecosystem-based management” has been an ecologically and economically
effective approach in marine conservation (Norse and Crowder 2005). But to specifically address
mitigation-based conservation, the analysis by
Wilcox and Donlan (2007) provides support for a new sort of “lifecycle-based management.”
Pilot programs would need political and economic leverage. After all, there is little
history of market externalities incorporated with the costs of fishing (Lewison, Crowder et al.
2004). Difficulties are likely to arise when integrating the model with existing management and
conservation regimes. Programs would only be effective in highly monitored fisheries with
existing bycatch reduction programs. Compensatory mitigation, however, may prove more costeffective and politically desirable than current command-and-control interventions, like fisheries
closures. Moreover, the model provides an opportunity to forge an innovative alliance between
conservation and fisheries organizations.
Mangrove-inhabiting fish, sea turtles, sea birds, and pinniped species warrant investigation under
this scheme. Most seabird conservation to date has concentrated on
bycatch and pollution at sea. Stress on “higher-profile” mortality sources, however, tend to
funnel conservation funds on projects that are too narrow in scope (Lewison, Crowder et al.
2004). Population growth of bycatch species can only be achieved once programs address the
threats species encounter in habitats far from open-ocean industry.
REFERENCES
Aburto-Oropeza, O., E. Ezcurra, et al. (2007). "Mangroves in the Gulf of California increase
fishery
yields." Proceedings of the National Academy of Sciences 105(30).
Faunce, C. and J. Serafy (2008). "Growth and secondary production of eventual reef fish during
mangrove residency." Estuarine, Coastal, and Shelf Science 79(1): 93-100.
Gilman, E., D. Kobayashi, et al. (2008). "Reducing seabird bycatch in the Hawaii longline tuna
fishery." Endangered Species Research (THEME ISSUE - Fisheries Bycatch: Problems and
Solutions).
Gobert, B., P. Berthou, et al. (2005). "Early stages of snapper-grouper exploitation in the
Caribbean." Fisheries Research 73(1-2): 159-169.
Howald, G., J. Galvan, et al. (2007). "Invasive rodent eradication on islands." Conservation
Biology 64.
Lewison, R. L., L. B. Crowder, et al. (2004). "Understanding the impacts of fisheries bycatch on
marine megafuana." Trends in Ecological Evolution 19: 598-604.
Norse, E. A. and L. Crowder (2005). Marine Conservation Biology: the Science of Maintaining
the
Sea's Biodiversity. Washington, Island Press.
Rotjan, R. and S. M. Lewis (2006). "Parrotfish abundance and selective corallivory on a Belizean
coral reef." Journal of Experimental Marine Biology and Ecology 335(2).
Wilcox, C. and C. Donlan (2007). "Compensatory mitigation as a solution to fisheries bycatch biodiversity conservation conflicts." Frontiers in Ecology and Environment 5(6): 325-331.