Female American lobster ( Homarus americanus ) size-at-maturity declined in Canada during the 20th and early 21st centuries

• Published in: Canadian journal of fisheries and aquatic sciences 2018-06, Vol.75 (6), p.908-924
• Main Authors: Haarr, Marthe Larsen, Sainte-Marie, Bernard, Comeau, Michel, Tremblay, M. John, Rochette, Remy
• Format: Article
• Language: English
• Subjects: Abundance; American lobster; Animal populations; Climate change; Crustaceans; Egg production; Environmental aspects; Environmental changes; Evolution; Exploitation; Fecundity; Females; Fish; Fish eggs; Fisheries; Fishery management; Fishery regulations; Fishing; Global warming; Harvesting; Homarus americanus; Invertebrates; Life cycle; Life history; Lobster fisheries; Lobsters; Marine; Maturation; Modelling; Natural history; Observations; Ocean temperature; Physiological aspects; Population density; Seafood; Sexual maturity; Shellfish; Size-at-age; Size-at-first-maturity; Size-limit regulations; Spawning stock biomass; Water temperature
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2016-0434

Changes in the environment and fishing have been shown to affect life-history characteristics, such as size or age of maturation, in a number of finfish and invertebrates. The American lobster (Homarus americanus) supports Canada's most valuable fishery and exploitation rates are high. Female size-at-maturity (SM) is an important parameter in management of this species, as it is used in establishing minimum legal size regulations. In this study, we show with historical and recent data that SM of female American lobsters has declined across most of Canada, in some areas by as much as 30%, over the past 10-80 years. The spatial patterns of these declines are inconsistent with patterns of rising ocean temperature and lobster abundance (density). They are, however, strongly correlated to the strength of size-based fishery selection, and egg-per-recruit modeling indicates a gain in lifetime egg production associated with observed SM declines under a range of realistic harvesting scenarios. These findings suggest that the marked decrease we document in SM of female American lobsters in Canada over the past century represents an evolutionary response to intense exploitation.