Can scientific observations of early life stages be scaled up to the level of a fished population? A case study using Homarus americanus

• Published in: Fisheries research Vol. 65; no. 1; pp. 33 - 46
• Main Authors: Incze, Lewis S, Wolff, Nicholas, Wahle, Richard A
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2003
• Subjects: Homarus americanus; Larvae; Life table; Lobster; Marine; Mortality; Postlarvae; Recruitment; Settlement; USA, Maine, Lincoln Cty; Homarus americanus; Settlement; Larvae; Lobster; Mortality; Postlarvae; Life table; Recruitment
• ISSN: 0165-7836; 1872-6763
• DOI: 10.1016/j.fishres.2003.09.005

Ecological studies of the early life stages of benthic crustaceans are typically conducted at small scale to measure processes such as settlement and survival and the factors that affect them. A test of the measurements is whether or not the results of such studies can be extrapolated successfully to the level of a population. Do the data and inferences fit within the geographic space and the relatively few, available population reference points? We address this question for the lobster fishery for Homarus americanus in Lincoln County, Maine, USA, by constructing a life table linking all stages from egg production to the fishery using an age-structured model. We used early life history data (postlarvae and early benthic stages) from 1989 to 1995 and fisheries data from 1995 to 2001, a time lag that is appropriate for newly settled lobsters to enter the fishery. We used inverse methods to estimate the total number of settlers (Young-of-Year) needed to maintain the population and harvest of the late 1990s at steady state; we then estimated the amount of habitat needed to accommodate those settlers based on observed settlement densities. This was compared to the available space identified using a geographic information system (GIS). We predict that the population of lobsters from which the fishery is extracted can be supported by YOY settlement in 7–16% of the sublittoral area shallower than 20 m, a proportion that surveys confirm is available. We obtained an average larval mortality rate of ≤0.07 per day and we estimated that ∼2.5% of planktonic postlarvae settle successfully. The amount of egg production inferred by the model is easily accounted for by the abundance of sexually mature females in a recent survey.