Spatial linkages between settling young-of-year and older juvenile lobsters

Abstract

We examined spatial association between young-of-year (YoY) and older juvenile (Juv) American lobsters Homarus americanus across multiple spatial scales using 8 years (2001 to 2008) of field measurements of a long-term settlement index time series from New England, USA.Complementary laboratory experiments examined behavioural responses of settling postlarvae to conspecific presence. Regional scale (10s to 100s of kilometres) data aggregation showed significant association between YoY recruitment and Juv densities in the same year for all 8 years examined. These broad-scale positive associations support previous research showing the importance of circulation-driven patterns of larval supply in linking newly settled YoY and Juv lobsters. Analysis at the quadrat scale, however, showed greater than expected association between YoY and Juv, suggesting a behavioural component. Early benthic-phase Juv lobsters (~0 to 2 yr old) strongly associate with structurally complex habitats; however, little is known of other habitat quality variables that may enhance successful recruitment. Resident conspecifics may represent one of several habitat quality proxies for postlarval lobsters despite post-settlement risk in settling among conspecifics, such as competition and predation. In short-term (4 min) laboratory behavioural experiments, postlarvae spent significantly more time on the bottom in the presence of conspecific juveniles. In longer-term (24 h) experiments, postlarvae initially (<1 h), though not significantly, settled more rapidly in the presence of conspecific juveniles, and any weak effect dis sipated with time. Lack of suitable habitat in experimental chambers may have inhibited a longer-term response. While conspecifics may initially attract postlarvae, settlement may require additional habitat cues.

Spatial surface temperature correlates of American lobster (Homarus americanus) settlement in the Gulf of Maine and southern New England shelf

“…The American Lobster Settlement Index (ALSI), an international collaborative of marine resource agencies and academic institutions, monitors recently settled YoY lobsters at more than 100 sites along the coast of New England and Atlantic Canada. The ALSI has significantly improved our understanding of the dynamics of early benthic phase lobster populations (Incze and Wahle 1991, Wahle and Incze 1997, Xue et al 2008, Burdett-Coutts et al 2014 and their relationship to landings (Steneck andWilson 2001, Wahle et al 2009a). Despite local (0.1-10 km) patchiness in settlement Incze 1997, Sigurdsson et al 2016), ALSI time series reveal large-scale (>100 km) spatial coherence, suggesting the considerable areas over which environmental drivers may operate in common (Pershing et al 2012).…”