Preliminary Review of Cusk, Brosme Brosme, Reproductive Biology in U.S. Waters Facilitated By a Cooperative Research Survey

Cusk, Brosme brosme, a deepwater species that prefers hard bottom habitats, has declined in abundance and is proposed as a NMFS candidate for listing under the Endangered Species Act (ESA). Evaluating their status is hampered by a lack of recent (< 30 years) and regional life history information.  A recently conducted cooperative bottom longline survey, targeting rocky bottom habitat in the Gulf of Maine, dramatically augmented the samples collected from the regional bottom trawl survey and other collaborating commercial vessels. Based on all samples collected, vitellogenesis of the annual clutch begins in fall. Spawning commenced in May and peaked during summer with some individuals spawning as late as November. Seasonal oocyte development patterns confirmed female cusk have determinate fecundity with group-synchronous oocyte development. The seasonal data indicated that both spring and fall survey data can be used to assess maturity. Macroscopic staging of females indicated nearly 100% maturity by 45 cm and was generally consistent with histological staging. Female fecundity and sex ratios at size were also examined. These data, gained largely from the cooperative research, will contribute to informing the ESA candidate listing and improving the assessment and management plans for this data poor species.