11th ICRS Abstract book - Nova Southeastern University

22-1
Complex Ecological Effects Of Fishing Revealed Using A New Assemblage
Assessment Tool That Relies On A Large Unfished Reference Area
Alan FRIEDLANDER* 1 , Joshua SLADEK NOWLIS 2 , Edward DEMARTINI 3 , Eric
BROWN 4
1 Biogeography Branch, NOAA, Waimanalo, HI, 2 Economics Department, Stanford
University, Stanford, CA, 3 Pacific Fisheries Science Center, NOAA Fisheries, Aiea, HI,
4 Kalaupapa NHP, National Park Service, Kalaupapa, HI
Scientific management guidance is lacking for most tropical marine fisheries because of
the exacting data requirements and many assumptions of conventional stock assessment
models. The lack of conventional advice often leads to management paralysis even
amidst strong claims about fisheries collapses based on analysis of limited or selective
data. We produced unconventional preliminary assessments for 55 species within the
main Hawaiian Islands (MHI) by comparing abundances there versus within the
Northwestern Hawaiian Islands (NWHI) Marine National Monument—a large, virtually
unfished reference area. Nearly three-quarters of the species appeared to be depleted in
the MHI with abundance levels less than 25% of the NWHI. Large mobile predators were
especially affected, but many other target and non-target species appeared to be in poor
condition as well. When small no-fishing areas within the MHI were used as reference
points, our impression of stock status would have been overly optimistic, particularly for
stocks in the worst condition. By comparing size frequency distributions for certain
species in the two areas, natural and fishing mortality rates were developed. Since NWHI
populations experience little fishing pressure, mortality rates there represent natural
mortality whereas the MHI populations experience both natural and fishing mortality.
Analysis of the highly prized blue trevally (Caranx melampygus) suggested that recent
fishing rates are almost double a reasonable proxy for maximum sustainable yield and
that the spawning potential ratio was 11% of reproductive potential. With the help of a
larger and therefore more appropriate unfished reference area, we were able to provide
strong evidence of depleted fish stocks likely caused by fishing on Hawaiian shallow
water reefs.
22-2
Current and Future Sustainability of Island Coral Reef Fisheries
Katie NEWTON* 1
1 School of Environmental Sciences, University of East Anglia, Norwich, United
Kingdom
Overexploitation is one of the principal threats to coral reef diversity, structure, function,
and resilience. Although it is generally held that coral reef fisheries are unsustainable,
little is known of the overall scale of exploitation or which reefs are overfished. Here, on
the basis of ecological footprints and a review of exploitation status, we report
widespread unsustainability of island coral reef fisheries. Over half (55%) of the 49
island countries considered are exploiting their coral reef fisheries in an unsustainable
way. We estimate that total landings of coral reef fisheries are currently 64% higher than
can be sustained. Consequently, the area of coral reef appropriated by fisheries exceeds
the available effective area by ~75,000 km2, or 3.7 times the area of Australia’s Great
Barrier Reef, and an extra 196,000 km2 of coral reef may be required by 2050 to support
the anticipated growth in human populations. The large overall imbalance between
current and sustainable catches implies that management methods to reduce social and
economic dependence on reef fisheries are essential to prevent the collapse of coral reef
ecosystems while sustaining the well-being of burgeoning coastal populations.
Oral Mini-Symposium 22: Coral Reef Associated Fisheries
22-3
The Need For Adaptive Management And The Challenges Of Climate Change
Brigid KERRIGAN* 1
1 Fisheries, Queensland Department of Primary Industries & Fisheries, Brisbane, Australia
The Great Barrier Reef World Heritage Area on the east coast of Australia supports an
ecologically sustainable coral and marine aquarium fin fish fishery. The collection of coral is
focused in two regions adjacent to large population centres which also support significant
tourism industries centred on the Great Barrier Reef. The collection of aquarium fin fish is also
concentrated in areas that typically have access to required land-based infrastructure. Due to the
operations of both fisheries they are highly visible and come under significant scrutiny from
stakeholders. To ensure the continuation of these fisheries within a World Heriatage Area both
management and industry are rethinking there approach. The added challenge is adapting
management and the operation of the fisheries to the potential changes in the coral reef system
that are/will occur in response to climate change. This paper outlines the adaptive comanagement
fisheries model being developed jointly by government and industry to deal with
the uncertain challenges of climate change and oppositional public opinion of a coral fishery
within the Great Barrier Reef World Heritage Area.
22-4
Coupled Changes in Structure And Function in Reef Fish Assemblages: How Predators
Increase Fisheries Production
Stuart SANDIN* 1
1 Marine Biology Research Division, Scripps Institution of Oceanography, La Jolla, CA
A growing number of surveys are revealing that coral reef ecosystem structure can vary greatly,
especially in response to anthropogenic stressors. Reef fish assemblages suffer a first line of
impact, with large-bodied, predatory species being disproportionately removed by fishing.
Despite consensus regarding such qualitative shifts in fish assemblage structure, we currently
lack detailed information about ecological consequences of these shifts. From the perspective of
reef fisheries, the basic question remains unanswered – how does alteration of fish assemblage
structure affect productivity, i.e., production of new fish biomass per unit time. Production is
the fundamental currency of fisheries management.
I have developed new analytical approaches to explore patterns of reef fish production, using
both theory and statistical estimators. I will demonstrate how trophic redundancy within reef
fish assemblages leads to very high energetic efficiency on reefs, and how such trophodynamics
can support fish assemblages dominated by predators (e.g., inverted trophic pyramids).
Systematic removal of top trophic levels (as by heavy fishing pressure) can dramatically shift
biomass and production patterns of lower trophic levels, resulting in reduced productivity from
the fish assemblage as a whole. Using visual count data collected across a dramatic gradient of
fishing pressure, I have estimated the realized changes in fishery production (in units of
instantaneous biomass production) that follow from reductions of predator biomass. Predators
systematically reduce the size of prey fish relative to species-specific size maxima, resulting in
a prey fish assemblage that is building more biomass through time. In the absence of predators,
prey fish are more consistently near their species-specific maximum size, and thereby shunt
more energy toward reproduction and respiration and less toward somatic production. Thus, the
interests of conservation and fisheries management appear aligned – by maintaining (or
rebuilding) predator populations, there is capacity to simultaneously maintain (or rebuild)
productivity of the fishery.
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