Harvesting the Sea - Commercial fishing and its effects on Osteichthyean andChondrichthyean fishes

Between 1950 and 1994, ocean fishermen increased their catch 400% by doubling the number of boats and using more effective fishing gear. In 1989, the world's catch leveled off at just over 82 million metric tons of fish per year. “That's all the ocean can produce. Sending more boats won't help us catch more fish”.

Wait a minute, catch has increased dramatically but fish/person has not!Why???

Human Population growth 1950 2.5 billion2000 6 billion

Fisheries collapse - The North Atlantic Cod Collapse

Recent, widespread collapse of fisheries

1950’s

Multiple ecological effects of overfishing

“Bycatch”Worldwide, fisheries throw away 25% of their catchFor each pound of shrimp caught in a trawl net, an average of two to ten pounds of other marine life is caught and discarded

Recent research: Nature 2006

Pacific coast of US: exploited fish species populations more variable from year to year than non-exploited

Ecology Letters 2006:

Overharvesting, especially of older fish, may rapidly lead to “Darwinian Debt” loss of genes coding for important characteristics like size, age at reproduction, egg size and number

Chilean seabass live at least 40 years, orange roughy at least 100. A Pacific rockfish caught in 2001 was 205 years old—born when Washington was still president! Such slow-growing fishes are very vulnerable to overfishing

Be Part of the Solution

By making better seafood choices using the Seafood Watch card (e.g. Monterey Bay Aquarium website www.mbayaq.org) you know which fish are caught with little bycatch. That way you can support responsible fishermen and help reduce wasted catch.

Major evolutionary events in Vertebrate History

1) Evolution of jaws and paired appendages

2) The Evolution of Tetrapods and Invasion of Terrestrial Environments

Devonian Age of Fishes- Ostracoderms, placoderms, acanthodians, chondrichthyes, actinopterygians, sarcopterygians, first tetrapods!!

Devonian conditions

Warm shallow seas

Land with primitive plants

Land with terrestrial invertebrates

Why important?

Lots of aquaticDevonian predators and competitors

So what?

Hypotheses about evolutionary forces driving invasion of the land

Eusthenopteron

Ichthyostega

Acanthostega

Evolution of Tetrapods – example of transitional forms