Population biology of monkfish Lophius americanus

Abstract

Richards, R. A., Nitschke, P. C., and Sosebee, K. A. 2008. Population biology of monkfish Lophius americanus. – ICES Journal of Marine Science, 65: 1291–1305. This paper provides an overview of the biology of monkfish in US waters of the Northwest Atlantic Ocean using data from resource surveys spanning the period 1948–2007. Monkfish exhibited seasonal onshore–offshore shifts in distribution, migrated out of the southern Mid-Atlantic Bight (MAB) in mid-spring, and re-appeared there in autumn. Sex ratios at length for fish 40–65-cm long were skewed towards males in the southern MAB, but approximated unity elsewhere, suggesting that a portion of the population resides outside sampled areas. Growth was linear at 9.9 cm year−1 and did not differ by region or sex. Maximum observed size was 138 cm for females and 85 cm for males. Length at 50% maturity for males was 35.6 cm (4.1 years old) in the north and 37.9 cm (4.3 years old) in the south; for females 38.8 cm (4.6 years old) in the north and 43.8 cm (4.9 years old) in the south. Ripe females were found in shallow (<50 m) and deep (>200 m) water in the south, and in shallow water (<50 m) in the north.

Estimating the Sex Composition of the Summer Flounder Catch using Fishery‐Independent Data

“…Spatial and temporal segregation of fish by sex is a common phenomenon and occurs in other sexually dimorphic flatfishes (Morgan and Trippel 1996;Swain 1997;Swain and Morin 1997;Gorchinsky 1998;Richards et al 2008;Gerritsen et al 2010;Sahin and Gunes 2010;Loher and Hobden 2012;Loher et al, in press). Explanations for sex-specific segregation include temperature selection (Swain 1997) and/or depth selection (Swain and Morin 1997), sex-specific life history strategies that promote sexually dimorphic characteristics (Gerritsen et al 2010), and sex-specific foraging intensity and the spatial and temporal distribution of the forage base (Swain and Morin 1996).…”

Goosefish Lophius americanus fecundity and spawning frequency, with implications for population reproductive potential

“…In the southern management area, Johnson et al . () confirm a single, sharp peak in the gonad‐somatic index of females during March (Armstrong et al ., ), coinciding with the largest proportions of females with mature oocytes observed; however, smaller proportions of females with mature oocytes persist in this southern area until August (Johnson et al ., ; Richards et al ., ). Mature females in the northern area have not been examined, but the ichthyoplankton data showed widely overlapping spawning seasons among latitudinal strata, with a later seasonal mode of spawning further north.…”

“…Sex ratio at age from survey data for each period was estimated; all L . americanus aged 8 years and older were female (Richards et al ., ). Females aged 4–12 years were included as these are fully recruited to the survey gear used to estimate population structure (Anon, ).…”

“…Females aged 4–12 years were included as these are fully recruited to the survey gear used to estimate population structure (Anon, ). Estimated age at 50% maturity for females is 4·9 years (Richards et al ., ). A recent study has suggested that the age determination methods of Armstrong et al .…”

“…Lack of information on the fishery, coupled with poor understanding of L . americanus biology, made it difficult to determine the status of the population when management of the species began (Richards et al ., ). Simple metrics, such as declining fish size in commercial landings, led to the implementation of the first fishery management plan for L .…”