Cod Gone?
JB: This is Earth and Sky. On our visit to the Museum of Science in Boston, Carol Belovitch asked about Atlantic cod:
Carol Belovitch: We went fishing in Gloucester yesterday and noticed a low level in cod. At what point under current conditions will the supply be totally depleted?
DB: Carol, it’s hard to predict if and when a fish species will disappear. It depends on fishing pressures and the health of fish populations. To evaluate the health of a population, scientists measure the mass of all the reproductively active individuals . . .
JB: That’s what’s known as the “spawning biomass.” The spawning biomass of cod to the south of the Gulf of Maine, on the Georges Bank, has been dangerously low for some years – although reproductively active cod in the Gulf of Maine, near Gloucester, have increased slightly.
DB: But here’s the tricky part. When the cod population decreases, the price of cod increases. So it’s profitable to fish for cod even when population numbers are spiraling downward. The New England Fishery Management Council recently passed revised regulations that aim to eliminate overfishing.
JB: Time will tell how well they’ll work to rebuild populations of cod. Special thanks to the National Oceanic and Atmospheric Administration and to the National Fish and Wildlife Foundation. We’re Block and Byrd for Earth and Sky.
Scientist replies:
From an email with Steve Murawski:
Dear Kathy,
Thanks for the question. Here goes for an answer:
First of all, the success or failure of any individual fishing trip is not necessarily indicative of the health of a population in the area (any dedicated angler or commercial fisherman knows this). This being said, however, the two cod stocks in New England waters (i.e., cod in the Gulf of Maine are considered distinct from those on Georges Bank and south), have experienced the effects of overfishing for about two decades. Both cod stocks continue to be overfished, which means that the rate of harvest exceeds a safe rate of removals for the population. For both cod stocks the target removal rate from fishing is about 20% per year. The other important yardstick for measuring stock status is the current condition of the spawning biomass – the mass of all the spawning aged individuals in the population. High spawning biomass generally equates to higher probabilities of good production of baby fish, year-to-year.
For Georges Bank the cod, spawning biomass is very low and has been so for several years. Without increases in the production of baby fish or substantial reductions in the rate of fishing, this stock will decline even more. For cod in the Gulf of Maine stock (the one contributing to catches off Gloucester) the abundance of spawners has actually increased in recent years due to a couple years of above average production of baby fish. The goal of stock rebuilding is to increase the cod stock in the Gulf of Maine by about a factor of three over where it is now. Revised regulations recently passed by the New England Fishery Management Council are intended to eliminate overfishing of cod and other species caught with it (flounders etc.) and rebuild populations to their target levels. For a number of other stocks, like haddock, where fishing rates have been lower than the maximum target rate, stock rebuilding has been relatively rapid. Hopefully cod populations will not be too far behind.
I hope this is not too long-winded for your purposes
cheers
-Steve Murawski
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From a phone call with Dr. Jake Rice:
Cod stocks in general are being depleted?.Fewer individuals and they are younger and smaller than historically. Old experienced parents produce young that are much healthier.
Factors:
1. The productivity is lower 2. Effectiveness of the fisheries decreases when cod catches are limited. This has to do with the fact that the price of cod increases when supply is limited. Also, when fisherman fish for healthier fish populations, like haddock, cod may get caught as a bycatch. The cod may be thrown back out, but may also die in the process- either in the water or boat. Some fisherman may also take the cod as they know that some markets will buy the on the black fish market for a high price. 3. Other predation pressures also increase relative to the population size when fish populations are low.
So the only way to curb depletion of cod stocks is to change the baseline conditions. No historical evidence of overfishing causing species extinction, but it may become uneconomical to fish the cod within the next few years. If people would comply with the recommended quotas, the stocks would start to recover.
The following people were interviewed for today’s program. Our thanks to:
Dr. Jake Rice
Canadian Stock Assessment Secretariat
Fisheries and Oceans Canada
Ottawa, Ontario, Canada
Dr. Steve Murawski
NOAA Fisheries
Northeast Fisheries Science Center
Woods Hole, MA
Additional Teacher Resources
Conservation Law Foundation; Natural Resources Defense Council: Deep Sea Rescue: Is Time Running Out For Georges Bank Cod?
The codfish helped to shape New England. But does it have a place in the regions future? This report explains how overfishing has decimated New England’s richest cod grounds in what is known as Georges Bank.
National Oceanic and Atmospheric Administration; Northeast Fisheries Science Center: Status of Fisheries Resources off Northeastern United States─Atlantic Cod
This informative report provides a brief natural history of the Atlantic Cod, followed by a look at the species current population trends. The article focuses commercial fishing and population trends in the Gulf of Maine as well as the Georges Bank Areas.
