The role of food limitation in lobster population dynamics in coastal Maine, United States, and New Brunswick, Canada

Abstract

Lobster (Homarus americanus) landings in Maine, United States have increased steadily over the past two decades to levels that are consistently more than triple the 40-year (1950 to 1990) annual average of c. 9000 MT. Meanwhile, the use of herring (Clupea harengus) as bait has increased fourfold since the 1970s, and is currently subsidising lobster productivity in mid-coast Maine by augmenting the diet and growth of large juvenile and young adult lobsters before they recruit to the fishery. We investigated whether herring bait in the eastern portions of the Gulf of Maine is also subsidising these lobster populations. Harbour consumed markedly more bivalves than those at Cutler. Furthermore, quantification of trap densities and the number of licensed fishers in midcoast versus eastern Maine determined that fishing effort was greatly reduced in eastern Maine. Thus, our results indicate thatherring bait subsidies are not important in eastern portions of the Gulf of Maine, but the availability of natural prey seemingly limits the growth of lobsters in eastern Maine. Moreover, our study suggests that bottom-up forcing (i.e., food limitation) can have important consequences for lobster population dynamics and the productivity of lobster fisheries.

Top-down control of lobster in the Gulf of Maine: insights from local ecological knowledge and research surveys

“…Bait inputs may be more substantial on the United States' side of the GOM, where trap density is higher and the fishery operates year-round (Myers et al 2007, Grabowski et al 2009). Despite the higher bait input, however, the relative increase in lobster landings has been less pronounced in the United States compared with Canadian waters (Myers et al 2007), and, in the eastern portions of the GOM, bait is not believed to subsidize lobster populations (Grabowski et al 2009). …”

Paralytic shellfish poisoning: Seafood safety and human health perspectives

“…However, the timing and overlap of scallop and lobster harvesting do not fully support the idea that discarded scallop tissues could be solely responsible for lobster toxicity. Lobster harvesting occurs throughout Maine coastal waters, with highest concentrations around Penobscot Bay in central Maine, and in this region lobsters have been found to have an extremely diverse diet (Steneck and Wilson, 2001;Grabowski and Gaudette, 2008). Lobster hepatopancreas toxicity has been found along the coast with highest concentrations in areas such as off Jonesport and Cutler (D. Couture, pers.…”

Description du régime alimentaire et comparaison de la niche alimentaire des larves de trois espèces de poisson fourragères dans le nord du golfe du Saint-Laurent :

“…Top-down forcing is not the only way that species abundance is regulated in an ecosystem, for instance, bottom-up effects caused by limited prey abundance have been observed in various aquatic ecosystems (Blanco et al, 2003;Brown-Saracino et al, 2007;Grabowski et al, 2009). Gliwicz (2002) pointed out that prédation and starvation mechanisms underling top-down and bottom-up effects are fundamentally different but usually work in conjunction to limit species abundance.…”