Accidental Conservation: Are Lobster Traps Helping Lobsters?

The American lobster is not a picky eater. A single study on a Nova Scotia population recorded such fare as seaweed, sponges, limpets, moon snails, periwinkles, whelks, flat skenia snails, mussels (their favorite), cockles, clams, chitons, bryozoans, barnacles, marine isopods, shrimp, crabs, other lobsters, sea cucumbers, sea stars, urchins, tunicates, fish, ragworms, scale worms, roundworms, ribbon worms, flatworms, happy worms, sad worms, wormy worms … you’ve probably skipped to the next paragraph by now, so I’ll stop. But this list is just an abbreviated version of the actual list, which is in the original paper (Elner and Campbell 1987) if you’re interested.

The point is, lobsters pretty much take what they get. That’s why lobstermen in the Gulf of Maine bait their traps with rotten herring — even though herring isn’t usually on the lobsters’ natural menu, the strong smell is enough to draw the curious crustaceans in.

An adult American lobster from Rhode Island. Photo by Rick Wahle, in public domain.

An adult American lobster (Homarus americanus) from Rhode Island. Photo by Rick Wahle, in public domain.

Once they get there, lobsters actually have a pretty good chance of getting away with a free meal. In 2002 a group of scientists planted cameras on lobster traps in New Hampshire to see how many lobsters were approaching traps on a nightly basis (Jury et al. 2002). Their results were astounding: of the lobsters that entered the traps to feed, only 6% stayed long enough to be caught. The rest escaped with bellies full of herring.

Roughly 70% of Atlantic herring caught in Maine ends up in a lobster trap. Photo by Chiswick Chap, licensed under CC BY-SA 3.0.

Roughly 70% of Atlantic herring caught in Maine ends up in a lobster trap. Photo by Chiswick Chap, licensed under CC BY-SA 3.0.

Unintentionally, lobstermen in the Gulf of Maine are providing lobsters with a portion of their diet. But just how important is bait herring to lobster populations in the wild? Grabowski and colleagues (2010) tried to answer this question by studying the diet of Maine lobsters. Using molecular markers in lobster stomachs, they compared the relative amounts of the most important natural prey (mussels, urchins, and crabs) with herring.

The results suggest that bait herring accounts for a whopping third to half of the total calorie intake of lobsters during the trapping season — once trapping ends for the year, only trace amounts of fish can be found in lobster stomachs. So herring is a major part of the lobster diet in heavily trapped areas of Maine, but is this good or bad for the lobsters?

These are juvenile American lobsters -- what they eat will affect how quickly they grow. Photo by Robert Huber, licensed under CC BY-SA 3.0.

These are juvenile American lobsters — what they eat will affect how quickly they grow. Photo by Robert Huber, licensed under CC BY-SA 3.0.

Grabowski and colleagues continued their research by recording the growth rates of wild lobsters both in heavily trapped and untrapped regions of Maine, as well as during and after the trapping season. They found that lobsters grew faster in heavily trapped areas than anywhere else, by about 15%. The same pattern was observed over several years, but the increased growth rate stopped soon after the trapping season ended, when bait herring was no longer on the menu.

Even though herring is rarely available to lobsters under natural conditions, bait herring is very nutritious and might help wild lobsters grow faster. If this is the case, the use of bait herring allows lobsters to reach maturity sooner, making Maine’s lobster fishery more sustainable. This is good news, both for lobsters and for the people and livelihoods that depend on them.

This article is a tribute to my time in Maine, where I grew up and where, this past weekend, I participated in the 13th annual BioBlitz at Acadia National Park. I also gave a public presentation on millipedes and centipedes at the Schoodic Education and Research Institute, which was a blast! You can watch the talk here.

Cited:

Elner R.W. and A. Campbell. 1987. Natural diets of lobster Homarus americanus from barren ground and macroalgal habitats off southwestern Nova Scotia, Canada. Marine Ecology Progress Series 37: 131-140.

Grabowski J.H., E.J. Clesceri, A.J. Baukus, J. Gaudette, M. Weber, and P.O. Yund. 2010. Use of herring bait to farm lobsters in the Gulf of Maine. PLOS One 5(4): e10188. doi: 10.1371/journal.pone.0010188

Jury S.H., H. Howell, D.F. O’Grady, and W.H. Watson III. 2002. Lobster trap video: in situ video surveillance of the behavior of Homarus americanus in and around lobster traps. Marine and Freshwater Research 52(8): 1125-1132.

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3 responses to “Accidental Conservation: Are Lobster Traps Helping Lobsters?

  1. Love this. So interesting. Glad there is a good use for rotten herring!

    Like

  2. If only six percent of lobsters who eat the herring are caught, then it must take an average of 16 days for a lobster trap to catch a lobster. Very inefficient – maybe someone should figure out a better way….

    Like

  3. Fascinating! Interesting to read that a diet of rotten herring is a delicious meal for a lobster.

    Like

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