Some observations on ecosystem-based fisheries management

Nandadulal Bairagi ( (Centre for Mathematical Biology and Ecology, De)

Friday 6th September, 2013 15:00-16:00 Maths 509


Overexploitation is the most responsible factor to the persistence of
harvesting stocks. It is believed that at least half of the fisheries
of Europe and USA are under stress due to over harvesting. According to
new paradigm of ecosystem-based fisheries management (EBFM), selective
fishing is widely promoted in contrary to nonselective fishing. For
example, species and age/size selection harvesting are widely
encouraged in fisheries management to avoid bycatch and to restrict
harvesting below a certain age or size, respectively. To verify
rationale of some of these recommendations in EBFM, we propose and
study a two species predator-prey fishery model where either or both of
prey and predatory fishes are subject to selective harvesting. Our
study reveals that a moderate delay in harvesting is beneficial to EBFM
but large delay may send species to unpredictable situation and could
be fatal for the species concerned and in the functioning of the
ecosystem as well. Our study specifically suggests that increased
harvesting of predator or decreased harvesting of prey fish species,
depending on the position of the species in the food chain, may be
effective to bring the system under control. It is also suggested that
a balance between harvesting delay and harvesting intensity should be
maintained for sustainable yield and better ecosystem management.

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