Massive decline of predatory fish in the last 100 years threatens ‘wild’ oceans

Friday, February 18th 2011 - 23:47 UTC

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Forage fish population doubled but to turned into fishmeal and fish oil

Researchers at the University of British Columbia say they have the strongest evidence to date that humans are indeed “fishing down the food web,” citing data that show predatory fish such as cod, tuna, and groupers have declined by two-thirds during the past 100 years, while small forage fish such as sardines, anchovy and capelin have more than doubled over the same period.

Led by Prof. Villy Christensen of UBC Fisheries Centre, a team of scientists used more than 200 marine ecosystem models from around the world and extracted more than 68,000 estimates of fish biomass from 1880 to 2007, the university said in a press release Friday. They presented the findings at the American Association for the Advancement of Science Annual Meeting in Washington, DC.

The UBC team found that 54% of the decline in predatory fish population took place in the last 40 years.

“Over-fishing has absolutely had a 'when cats are away, the mice will play' effect on our oceans,” said Christensen, a professor in the UBC Fisheries Centre, in the release.

“By removing the large, predatory species from the ocean, small forage fish have been left to thrive.”

While the doubling of forage fish amounts to more fish production, Christensen cautioned that the smaller fish are more vulnerable to environmental fluctuations.

“Currently, forage fish are turned into fishmeal and fish oil and used as feeds for the aquaculture industry, which is in turn becoming increasingly reliant on this feed source,” said Christensen in the release.

“If the fishing-down-the-food-web trend continues, our oceans may one day become a ‘farm’ to produce feeds for the aquaculture industry. Goodbye, Wild Ocean!”

Christensen’s presentation was part of a panel discussing if there will be fish in the ocean in 2050. The prediction: yes, there will be fish, but they will consist mostly of the smaller variety.

Categories: Environment, Fisheries, International.

Tags: Fisheries.

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DennisA
This is yet more modelling, “more than 200 marine ecosystem models from around the world and extracted more than 68,000 estimates of fish biomass from 1880 to 2007.” This is using different data sets and types and is a simplistic straight line extrapolation. Biological populations don't work like that. For example in the severe cold of the 1960's Icelandic cod moved south, so were in decline in Iceland and led to the Cod wars between Iceland and the UK.
Feb 19th, 2011 - 08:21 am 0
Tim Burford
Err yes Dennis, it's modelling - the alternative is for you to sieve through the world's oceans and give us a reliable count of every fish species. Off you go now.
Feb 19th, 2011 - 09:56 am 0
thewhalepeople.com
Wonderful reply to Dennis; I think it will be some “added time” before he gets back to you...

I think it also works with whales. You see, orcas are not hunted and protected by most countries. Since their populations are on the increase, so is their appetite. And in part, their appetite are juvenile/ whale calves like the gray whale. And calf populations are down. That means less population growth of whales, both from internal (marine) and external (man) pressure.

As for the rest of the marine population, we already see these declines and it is, as you say from man's over-fishing. A small island country, packed with sefood loving people (Japanese) consume 2000 tuna per day. One only has to “do the math” to recognize that with trawlers that can catch up to 7,000 tuna at one netting, it is no wonder our seas are under siege.

Even with some “fishing controls” in place, violations are rampant. Witness the fact of Japanese fisherman caught bribing Russian fishing official to “look the other way” or ignore their actual catches.

It is blogs like yours and mine that help raise the awareness of people worldwide to this growing problem - one cannot farm fish, only deplete the system.
Feb 19th, 2011 - 07:00 pm 0

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