Nonconsumptive effects of a range‐expanding predator on juvenile lobster (Homarus americanus) population dynamics

Abstract

Distribution shifts poleward are a widespread response to climate change and can result in altered community composition and interactions among species that previously were geographically isolated. The novel communities and species interactions that may arise during range shifts provide an opportunity to study fundamental ecological processes, while also addressing potential conservation issues. Black sea bass (Centropristis striata) historically ranged from the Gulf of Mexico to Cape Cod, but recently have expanded north into the Gulf of Maine. Very little is known about the impact of this range expansion on benthic community structure throughout the coastal waters of the Gulf of Maine. To investigate the effects of sea bass on the behavior of juvenile American lobsters (Homarus americanus), we manipulated the presence of sea bass olfactory cues and quantified shelter use and foraging behavior of lobsters from three regions in the Gulf of Maine with different potential contact histories with sea bass. Sea bass presence increased shelter usage and reduced foraging in lobsters, but contact history influenced the strength of these behavioral responses. Lobsters with no previous contact with sea bass did not significantly increase shelter usage or decrease movement in their presence but did reduce their foraging rate on mussels. This observed reduction in consumption indicates that naïve lobsters recognize novel predators, but the ineffective anti‐predator responses exhibited support the naive prey hypothesis. Meanwhile, lobsters with the longest potential contact history with sea bass significantly increased shelter usage when sea bass were present; however, they exhibited limited movement and foraging behavior in both the absence and presence of sea bass. Finally, lobsters with a short potential contact history with sea bass exhibited increased shelter usage, reduced movement, and reduced mussel consumption in the presence of sea bass, revealing that juvenile lobsters quickly adapt anti‐predator defenses to avoid this novel threat. Overall, these results suggest that prey contact history with novel predators mediates the strength of their nonconsumptive effects, and consequently can influence geographic patterns in predator–prey dynamics.

Range edges of North American marine species are tracking temperature over decades

“…This could arise due to density-dependent habitat selection if these species were declining in abundance, causing each range edge to collapse toward the range center (Blanchard et al, 2005). At the equatorward edge, competition or predation from the south could be driving edge retraction (Kordas et al, 2011); for example, the rapid contraction of the equatorward range edge of American lobster could be due to increased predation from species like black sea bass shifting up the coast (McMahan & Grabowski, 2019) or increased mortality from a temperature-related disease (Groner et al, 2018). At the poleward edge, species interactions (HilleRisLambers et al, 2013), priority effects (Fukami, 2015), dispersal limitation (Poloczanska et al, 2011), or a lack of non-thermal habitat (McHenry et al, 2019) could all inhibit northward shifts.…”

Range edges of North American marine species are tracking temperature over decades

“…This could arise due to densitydependent habitat selection if these species were declining in abundance, causing each range edge to collapse toward the range center (Blanchard et al 2005). At the equatorward edge, competition or predation from the south could be driving edge retraction (Kordas et al 2011); for example, the rapid contraction of the equatorward range edge of American lobster could be due to increased predation from species like black sea bass shifting up the coast (McMahan and Grabowski 2019) or increased mortality from a temperaturerelated disease (Groner et al 2018). At the poleward edge, species interactions (HilleRisLambers et al 2013), priority effects (Fukami 2015), dispersal limitation (Poloczanska et al 2011), or a lack of non-thermal habitat (McHenry et al 2019) could all inhibit northward shifts.…”

Overwintering survivorship and growth of young-of-the-year black sea bass Centropristis striata

“…The Northwest Atlantic is one of the fastest warming regions in the ocean [23]. Centropristis striata, the most northerly-distributed grouper species (Family Serranidae) in the Northwest Atlantic [26], has seemingly responded to the warming in this region as evidenced by higher abundances in the northern extent of their historic range [27] and by expanding their geographic range to the extent that they are now commonly found in the southern Gulf of Maine during spring and summer [28][29][30] where they had only been found occasionally in the past [26]. One potential mechanism for this range expansion is that overwintering mortality is reduced as temperatures on the Northeast shelf have increased.…”