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Spiny dogfish (Squalus acanthias) are assumed to be a highly migratory species, making habitual north-south migrations throughout their northwestern Atlantic United States (U.S.) range. Also assumed to be a benthic species, spiny dogfish stock structure is estimated through Northeast Fisheries Science Center (NEFSC) bottom-trawl surveys. Recent anomalies in population trends, including a recent four-fold increase in estimated spawning stock biomass, suggest alternative movement patterns could exist for this shark species. To obtain a better understanding of the horizontal and vertical movement dynamics of this species, Microwave Telemetry pop-up satellite archival X-Tags were attached to forty adult spiny dogfish at the northern (Gulf of Maine) and southern (North Carolina) extents of their core U.S. geographic range. Reconstructed geolocation tracks ranging in lengths from two to 12 months suggest that the seasonal migration patterns appear to be local in nature to each respective northern and southern deployment site, differing from previously published migration paradigms. Differences in distance and direction traveled between seasonal geolocations possibly indicate separate migratory patterns between groups. Kernel utilization distribution models also suggest strong separate core home ranges. Significant differences in seasonal temperature and depths between the two regions further substantiate the possibility of separate regional movement patterns between the two groups. Vertical utilization also suggests distinct diel patterns and that this species may not utilize the benthos as previously thought, potentially decreasing availability to benthic gear.

In the current study, plasma steroid hormones were used to assess the individual variability of Leucoraja erinacea over the course of 12 months, in hopes of further defining its reproductive cycle. No statistical differences in hormone concentrations were observed between the isolated and non-isolated female skates. Monthly E2 concentrations ranged from 1,430 pg ml(-1) in August to 3,940 pg ml(-1) in March, indicating the presence of mature ovarian follicles and supporting the conclusions from previous studies that L. erinacea is capable of reproducing year-round. Concentrations of E2 were significantly elevated or depressed during some months (February, March, June, July, August, and September) of the year, suggesting that reproductive activity may vary over the annual cycle. Even though monthly P4 concentrations were highly variable, ranging from 82 pg ml(-1) in November to 816 pg ml(-1) in September, no significant reproductive peaks were observed. In addition, a persistently large variation in E2 and P4 concentrations, indicative of reproductive asynchrony within (mean CV 62% and CV 69%, respectively) and between (mean range CV 78 and 125%, respectively) individual skates, was observed throughout the study. Collectively, the continually high E2 concentrations and variability in both hormones observed in the current study are indicative of an oviparous species that reproduces actively throughout the year. However, the weekly sampling frequency revealed that plasma E2 concentrations, not P4, were more useful to assess reproductive status in asynchronous continuously breeding oviparous elasmobranchs.

Age and size at sexual maturity was determined for 185 male and 96 female smooth skates Malacoraja senta (ranging in size from 370 to 680 mm total length L(T)), collected from the western Gulf of Maine. Maturity ogives for males, based on clasper length, testis mass and the proportion of mature spermatocysts in the testes, suggest that 50% maturity occurs between 9 and 10 years and 560 mm L(T). Maturity ogives for females, based on ovary mass, shell-gland mass and maximum follicle size, suggest that 50% maturity occurs at age 9 years and 540 mm L(T).

Size and age estimates at sexual maturity were determined for 162 male and 273 female little skates Leucoraja erinacea collected from the western Gulf of Maine. Maturity ogives suggest that 50% maturity in females occurs at age 9.5 years and 480 mm total length (LT), whereas 50% maturity in males occurs at a slightly younger age of 7.7 years and smaller size of 460 mm LT. Age estimates were made from 389 L. erinacea ranging in size from 93 to 570 mm LT. The index of average per cent error and age-bias plots indicated that the ageing methods were precise and non-biased. Additionally, annual periodicity of band formation was validated with oxytetracycline in eight individuals (three males and five females) ranging in age from 3 to 12 years. In conclusion, results from this study indicate that L. erinacea exhibits characteristics that make other elasmobranch populations highly susceptible to overexploitation.