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Harvesting Strategies for “Bianchetti” and “Blue Fish” in the Ligurian Sea (North Mediterranean) |
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PP: 861-874 |
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doi:10.18576/amis/100305
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Author(s) |
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Samrat Chatterjee,
Daniela Pessani,
Ezio Venturino,
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Abstract |
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| A three level trophic fish web model is proposed, consisting of clupeiforms pilchard (Sardina pilchardus) and anchovy
(Engraulis encrasicolus), at the bottom, mackerel (Scomber scombrus) in the intermediate trophic level and tunny (Thunnus thynnus)
as top predators. The model includes human harvesting. The clupeiforms population is further partitioned into three age classes, eggs,
larvae and the adult fishes to account for possible cannibalism but mainly for the fact that these larvae in the Mediterranean countries
are highly appreciated as a delicacy for human consumption. In the absence of fisheries, to prevent total extinction and maintaining
coexistence it is important that a sufficient amount of eggs fertilize to form larvae. The predation rate of larvae by other fish populations
also has an important role, especially for the occurrence of periodic solutions. Different harvesting policies are then numerically
simulated. Independently of the harvesting policy used, even a small amount of selective harvesting of larvae may cause total extinction
of the system. To prevent it, fishing that avoids the catch of the larvae should be adopted. With non selective harvesting the system is
preserved, but for certain parameter ranges oscillations arise, which under unfavorable environmental perturbations may lead the food
chain to collapse. |
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