Don't Just Take the Biggest Fish

Lay off the big fish, scientists say

...Published this week in the British journal Nature, the study suggests that the strategy of taking the bigger, older fish out of a population - commonly cited as a sustainable fishing practice - in fact makes the population more unstable, and more likely to go extinct...

The history of fisheries management is rife with stories of fisheries that became commercially extinct after heavy fishing, often heavily regulated.

...When a fish population fluctuates greatly in size, it has a greater risk of extinction and is harder to manage successfully, according to co-author George Sugihara of the University of California in San Diego. "If fishing results in both higher variability and declining populations, fisheries are in double jeopardy."

"All fish, including those that are not commercially harvested have ... ups and downs in response to natural changes in the environment. What we found is that these relative ups and downs are amplified in commercially fished populations," said Sugihara.

The authors think that the increased variability in exploited fish populations is due to the practice of fisheries selectively targeting bigger, older fish...

So the idea is that big fish do better some years, small fish do better others, and over the long haul, having both in population makes the population more stable:

...Sugihara explained that this is why it's important to maintain a good mix of big and little fish in the population. A population consisting of only little fish can "boom and bust," he said.

"Currently fisheries are managed in terms of specifying a 'total tonnage' for the catch," according to Sugihara. "Our results suggest that some attention should also be given to not just 'how much is harvested' but also to 'who is harvested.'"

Our striped bass are partially managed on this basis.  In Maryland during summer and autumn fishing on the larger fish, 28 inches and up is restricted to one a day, compared to 2 per day for fish between 18-28 inches. Commercial fisherman aren't supposed to take any larger than 36 inches.  However, we have a spring season where only the larger fish (usually 28 inches or greater) may be taken, the same larger fish that have an open season on them up and down the coast, wherever they visit in their migration.  And to all appearances, IMHO, stripers are headed for another population crash.

Released to swim again.