fisheries web

Who are you going to eat today?

Face it guys – you are predators!

These are fins confiscated from the illegal practice of shark ‘finning’ in Palau.

Sharks are caught in nets on on longlines; the fins and tails removed and the still-living sharks are tossed overboard.

Overexploitation of wildlife can threaten the survival of plant and animal species.

Even if a species is not at immediate risk of extinction, overharvesting can result in the collapse of a fishery, for example

“But the Earth is SO big! Can fishing fleets really cause long-term damage to the oceans?”

Bottom trawling scars on seafloor of Gulf of Mexico

Effects of bottom trawling on a New Zealand seamount

Trawled Untrawled

Is it possible to provide for sustainable fisheries that reduce environmental damage?

Orange Roughy “Slimehead”

Patagonian Toothfish (Chilean Sea Bass)

Do you see how the annual catch rates for Orange Roughy is dropping?

Trophic structure is a key factor in community dynamics

Every community has a trophic structure:

a pattern of feeding relationships consisting of several different levels and different types of interactions.

These interactions generate a food web.

1. Phytoplankton utilize photosynthesis to harvest sunlight and generate new biomass

3. Small invertebrates like krill eat the phytoplankton.

5. Small fish eat the krill.

4,5,6. Progressively larger predators consume smaller fish

Where do humans fit in this simple food web?

Convention on the Law of the Sea - adopted by the UN in 1982

Allow for economic zones extending 200 nautical miles into open ocean.

Managing marine fisheries fell to coastal countries

Well-orchestrated limits on annual fish ‘takes’ are needed to allow adult fish the opportunity to reproduce.

Juvenile fish need the time to mature so the fishery can recover.

Future regulation will be difficult to enact and enfore!