Publisher : International Council for the Exploration of the Sea
Place of publication :
Publication year : 2000
Thematic : Fisheries
Language : English
Note
"The impact of fishing on chondrichthyan stocks around the world is currently the
focus of considerable international concern. Most chondrichthyan populations are of
low productivity relative to teleost fishes, a consequence of their different life-history
strategies. This is reflected in the poor record of sustainability of target shark fisheries.
Most sharks and some batoids are predators at, or near, the top of marine food webs.
The effects of fishing are examined at the single-species level and through trophic
interactions. We summarize the status of chondrichthyan fisheries from around the
world. Some 50% of the estimated global catch of chondrichthyans is taken as
by-catch, does not appear in official fishery statistics, and is almost totally unmanaged.
When taken as by-catch, they are often subjected to high fishing mortality directed at
teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have
been virtually extirpated from large regions. Some chondrichthyans are more resilient
to fishing and we examine predictions on the vulnerability of different species based on
their life-history and population parameters. At the species level, fishing may alter size
structure and population parameters in response to changes in species abundance. We
review the evidence for such density-dependent change. Fishing can affect trophic
interactions and we examine cases of apparent species replacement and shifts in
community composition. Sharks and rays learn to associate trawlers with food and
feeding on discards may increase their populations. Using ECOSIM, we make some
predictions about the long-term response of ecosystems to fishing on sharks. Three
different environments are analysed: a tropical shelf ecosystem in Venezuela, a
Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem."
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Encoded by : Mae Belen Llanza
