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Scraping Bottom
by -- November 10th, 2015

It’s late autumn, so the season for bottom trawling has begun in Cobscook Bay, in eastern Maine. First, fishermen pursue sea urchins and later scallops. I am a fan of fresh scallops, so I appreciate their efforts to catch scallops on the cold mornings in mid-winter.  Even though no one seems entirely happy about rules, both harvests are closely regulated in an attempt to prevent destruction of these fisheries.   Let’s hope the rules work.

One does not have to travel far in Downeast Maine to see what overfishing can do to coastal villages and the people who work there. First the cod disappeared, then the herring, and finally the sardines.  There is much finger pointing at who was responsible—Russian trawlers, fish-locating sonar technology, dams on the rivers, EPA rules, and local greed.  But, the fish are gone, fish canneries are abandoned, and much of the population has left town. Even where protected, cod show only a slow recovery, suggesting that permanent changes have occurred in the ecosystem.

What happened in this area of coastal Maine is similar to what is reported from fisheries worldwide. The most desirable, large predatory fish, such as swordfish and snapper, are first depleted. By some estimates their numbers in the sea are only about 10% of what they once were.  Then fishermen focus on smaller species that were once considered trash fish.  Non-selective bottom trawling is employed, reworking, degrading, and denuding the deep sea floor at a rate that is roughly similar to the rate of deforestation that we deplore in the Amazon Basin. Finally, sardines and menhaden are the target of the catch.

This pattern exemplifies what Dan Pauly once called “fishing down” marine food webs, in which humans first exploit the top predators, then their prey, and finally the small fishes that support all of the marine food web. Roughly 8% of the total productivity to the seas goes to support the human population globally.  If we could see beneath the waters and knew how things have changed, we’d deplore what we would see.

In our local community, there are fishermen in pursuit of clams, lobsters, urchins and scallops. Their work is cold, tough and demanding.  Interestingly, compared to 50 years ago, no one makes a living from traditional fishing, except for those working with farm-raised salmon in large pens.

Now, there is an increasing urge to harvest seaweed, known as rockweed, which lines the coast. With the fishes gone, it is time to scrape the rocks clean of seaweed that once offered a nursery for the fisheries in the open waters.  If we are ever to see these fisheries recover, protecting rockweed will be an important foundation for the effort.  Observations also suggest that rockweed is an important nursery for the young of shellfish and lobsters.

Whether appropriate rules will be put in place to maintain adequate rockweed habitat, productivity, and regeneration remains to be seen. Already, those exploiting rockweed are lining up to defend their practice.  Claims that these folks are simply trying to make a living are tough to ignore, but scientific studies to support claims of a sustainable harvest are as scarce as cod fish.

 

References

Ames, E.P. and J. Lichter. 2013. Gadids and alewives: Structure within complexity in the Gulf of Maine. Fisheries Research 141: 70-78.

Frank, K.T., B. Petrie, J.S. Choi, and W.C. Leggett. 2005.   Trophic cascades in a formerly cod-dominated ecosystem.  Science 308: 1621-1623.

Jackson, J.B.C., et al. 2001. Historical overfishing and the recent collapse of coastal ecosystems.  Science 293{ 629-638.

Myers, R.A. and B. Worm. 2003. Rapid worldwide depletion of predatory fish communities.  Science 423: 280-283.

Pauly, D., V. Christensen, R. Froese, and M.L. Palomares. 2000. Fishing down aquatic food webs. American Scientist 88: 46-51.

Pauly, D. and V. Christensen. 1995. Primary production required to sustain global fisheries.  Nature 373:255-257.

Puig, P., M. Canals, J.B. Company, J. Martin, D. Amblas, G. Lastras, A. Palaniques and A.M. Calafat. 2012. Ploughing the deep sea floor.  Nature 489:286-289.

Rose, G.A. and S. Rowe. 2015. Northern cod comeback.   Canadian Journal of Fisheries and Aquatic Sciences 1789 doi: 10.1139/cjfas-2015-0346

Seeley, R.H. and W.H. Schlesinger. 2012.  Sustainable seaweed cutting?  The rockweed (Ascophyllum nodosum) industry of Maine and the Maritime provinces.  Annals of the New York Academy of Sciences 1249:84-103.

Watling, L. and E.A. Norse. 1998. Disturbance of the seabed by mobile fishing gear: A comparison to forest clearcutting.  Conservation Biology 12: 1180-1197,

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