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Annis, E.R., Wilson, C.J., Russell, R., Yund, P.O. (2013) Evidence for thermally mediated settlement in lobster larvae (Homarus americanus). Can. J. Fish. Aquat. Sci. 70: 1641–1649.

 ABSTRACT

We examined the potential for bottom temperatures ≤12°C to inhibit successful recruitment of planktonic lobster postlarvae to the benthos.  In laboratory trials, postlarvae held at 11°C exhibited higher mortality, slower development, and reduced size increase at molt relative to postlarvae held at 13°C. We sampled at field sites within Machias Bay, Maine (mean bottom temperature 12.39°C, 46.1 degree days ≥12°C) and at the mouth of the bay (mean bottom temperature 11.57°C, 5.1 degree days ≥12°C), where temperature was influenced by the cold Eastern Maine Coastal Current (EMCC).  We found significantly higher settlement at the warm inshore site but the abundance of competent planktonic postlarvae was not significantly different between sites, indicating a disconnect between postlarval abundance and settlement.  Regional sampling of newly settled lobsters revealed a pattern of higher settlement at inshore sites extending across a broader coastal region impacted by the EMCC.  Our results suggest that small differences in water temperature may shape settlement patterns through either behavioral avoidance of colder settlement sites or elevated post settlement mortality of postlarvae settling at colder sites.

Using a neuston net to sample lobster larvae and post-larvae in Machias Bay.  Lobster larvae are typically most abundant near the surface of the water.  Sampling at the mouth of Machias Bay and further up the bay (in the vicinity of Bare Island) indicated that larvae were equally abundant throughout the bay, but benthic sampling revealed that settlement densities were much higher at the up-bay sites.  Consequently, settlement density does not appear to be driven by larval supply; larvae appear to actively select warmer up-bay habitats in which to settle.

Wilkinson, E.B., Grabowski, J.H., Sherwood, G.D., Yund, P.O. (2015) Influence of predator identity on the strength of predator avoidance responses in lobsters. Journal of Experimental Marine Biology and Ecology 465: 107-112.

ABSTRACT

The American lobster, Homarus americanus, is an important benthic consumer in the Gulf of Maine and supports an extremely valuable fishery in New England and eastern Canada. Meanwhile, there is substantial interest in restoring large predator fish species to the Gulf ofMaine, and these predators may impact lobster populations both by consuming them and by inducing them to alter their behavior. Lobster tethering experiments were used to examine the susceptibility of a range of lobster size classes to predation in Saco Bay,Maine. The most susceptible sizes of lobsters were then exposed to three different fish predators (Atlantic striped bass Morone saxatilis, Atlantic cod Gadusmorhua, and sea raven Hemitripterus americanus) separately in experimental mesocosm tanks. Juvenile lobsters moved less and spent more time in shelterwhen in the presence of cod or sea raven. By contrast, striped bass did not induce lobsters to alter their behavior. Striped bass are highly mobile, active pursuit predators, which are thought to induce weaker behavioral responses in prey than sit-and-pursue predators like sea ravens. Thus, differences in lobster sheltering behavior corresponded with differences in predator foraging behavior. These predator-induced changes in behavior can result in less foraging activity, which may translate into reduced lobster growth and reproduction. Efforts to model marine communities and ecosystems will benefit from a more holistic understanding of whether predators induced prey to modify their foraging behavior and habitat usage.

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