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Oceans Need Broader Management Perspective
By Cat Lazaroff

WASHINGTON, DC, October 29, 2002

(ENS)

Ocean ecosystems are being strained by pollution, coastal development and harmful fishing practices, warns a new study from the Pew Oceans Commission. These human caused problems are endangering the ecological and economic benefits produced by some of Earth's most diverse and productive ecosystems.
The combined effects of overfishing, bycatch of non-targeted species and habitat degradation,are altering the composition of ecological communities, and the productivity and resilience of marine ecosystems, argues the Pew Commission report, "Ecological Effects of Fishing in Marine Ecosystems of the United States."
The report, the latest in a series of studies of the threats facing the nation's oceans, scientists find that many current fishing activities are harming the ecosystems on which future fishing depends, and that this phenomena is worsening. Leon Panetta, chair of the Pew Oceans Commission, released the report on Monday in conjunction with the California and the World Ocean Conference in Santa Barbara, California.

Ocean ecosystems are not unlimited resources, the report warns.
(Photo courtesy Ocean-Atmosphere Carbon Exchange Study)

"For centuries, we have viewed the oceans as an infinite resource beyond our capacity to harm. We now know that this is not true," said Panetta. "Our oceans are more vulnerable and more valuable than we ever imagined. If we want to sustain America's proud fishing industry, then we need to take a hard look at how pollution, development and fishing activities are harming the oceans."
In their report to the Commission, authors Paul Dayton of the Scripps Institution of Oceanography, Simon Thrush of the National Institute of Water and Atmosphere Research in New Zealand, and Felicia Coleman of Florida State University, find overwhelming evidence that the unintended consequences of fishing on marine ecosystems are "severe, dramatic, and in some cases, irreversible."
The report finds that certain fishing activities can deplete populations of fish and other marine species, which in turn alters food webs and ecosystems. By removing top predators, such as sharks and tuna, fishing can disrupt predator-prey relationships.
Fishing can also endanger marine mammals, seabirds, sea turtles, and certain species of fish, which are caught accidentally by drift nets, long lines and other indiscriminate fishing equipment. Other equipment, such as bottom trawl nets that rake the sea bottom, may alter the very structure and function of marine habitats.

Ocean predators like this pod of orcas in Frederick Sound, Alaska,
may go hungry when humans overfish their prey.
(Photo by Commander John Bortniak courtesy NOAA)

"If we are serious about saving our fisheries and protecting the sea's biodiversity, then we need to make swift, and perhaps painful, decisions to preserve and maintain the oceans' ecosystems," said Dr. Dayton, lead author on the report. "The time has come to reorient fishery management around the goal of protecting ecosystems and to instill flexible management that emphasizes caution."
The report's authors address three primary threats to the long term health of ocean ecosystems: overfishing, bycatch and habitat damage.

Overfishing

Worldwide, some 25 to 30 percent of all commercial fisheries are experiencing some degree of overfishing, with an additional 40 percent heavily or fully exploited. In the United States, where the federal government knows the status of just one-third of the stock it manages, a 2001 report by the National Marine Fisheries Service (NMFS) found that about one-third of the stocks for which the status was known were either overfished or experiencing overfishing.
The Pew Commission report finds that one result of overfishing is the decreased prey available to predators, often times resulting in a ripple effect throughout an ecosystem. This phenomenon is compounded by what is often called "serial overfishing," where fishers move from one species to the next as populations decline.
A final concern is what is termed "fishing down the food web," where fishing shifts from top predators to their prey and other species lower in the food chain, resulting in a top down ecological disruption.

Bycatch

Thousands of fish have been killed as bycatch in this shrimp haul.

Scientists estimate that up to 25 percent of the world's
fisheries catch is bycatch: invertebrates, fish, seabirds,
turtles and marine mammals accidentally captured along
with target species and discarded either dead or dying.
Bycatch has depleted most species of turtles,
many marine mammals, several species of albatross,
and several skates and rays.
The report finds that bycatch extends the effects of
fishing to a much wider sector of ocean life, with
repercussions to both the functioning and diversity of
ecosystems.

(Photo courtesy NOAA)

Habitat Disturbance

Protecting essential habitat from human activities is a vital component of successful fishery management, the report argues. Fishing activities can have temporary and long term effects on habitat such as rocky ledges, seagrass beds, sponge gardens and shellfish beds. All of these habitats are crucial to the growth and survival of juvenile fish, and serve as the focal point for many foraging and spawning adults.