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Here we introduce a new integrated population model (IPM) to provide harvest advice for the Gulf of St. Lawrence (Gulf), Coastal Nova Scotia (CNS) and Sable Island grey seal herds, and compare model outputs with estimates from a deterministic model used in previous assessments. The IPM was fit to the pup production estimates for the Scotian Shelf (CNS and Sable Island combined) and the Gulf. As with the previous assessment model, the new model was fit to both pup production and pregnancy rates, and includes an index for ice-related pup mortality in the Gulf. The new model includes both density-dependent and density-independent pup mortality, and fits to sighting histories of individually marked seals at the breeding colony on Sable Island to estimate sex- and age-specific survival and recruitment to the breeding colony. The model estimated that total pup production increased slightly from 92,300 (95% CI = 86,700-100,100) in 2016 to 99,300 (90,900-107,700) in 2021, while total abundance increased slightly from 339,400 (317,900-361,500) in 2016 to 366,400 (317,800-409,400) in 2021. The rate of growth of the population has continued to slow, declining from approximately 4% during the last assessment period, to 1.5% per year between 2016 and 2021. The updated population estimate from the previously accepted deterministic population model was 363,600 (298,700-450,000) for 2021, which is very similar to the estimate of abundance generated using the IPM. Although the population continues to grow, the current estimate is below that presented during the 2016 assessment. The difference is due to changes in the structure of the new population model and higher estimates of juvenile mortality produced by the model fit to the 2021 pup production estimates. Additional information on juvenile survival and how it responds to changes in abundance (density-dependent) and environmental (density independent) variation is needed as it represents a significant gap to our understanding of the dynamics of this population and of large marine mammals in general. Total allowable removals depend on age structure of the harvest and whether the harvests are conducted in winter at the breeding colonies, or at other times of the year when animals from all herds are mixed. Using an integrated model incorporates many of the inputs in a unified framework that allows for uncertainty to be propagated throughout the analyses. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Science Advisory Secretariat Research Document is the property of Her Majesty the Queen in Right of Canada as represented by the Minister of Fisheries & Oceans and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Science Advisory Secretariat Research Document is the property of Her Majesty the Queen in Right of Canada as represented by the Minister of Fisheries & Oceans and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

After more than four decades of growth at 13%, the rate of pup production of Grey Seals (Halichoerus grypus) at Sable Island has declined to about 4% per year. As resource limitation becomes more acute, life history theory suggests that first juvenile survival, then adult fertility, and finally adult survival will change. Previously, mark-resight analysis of Grey Seals on Sable Island found that juvenile survival had been reduced by almost 50% between the early 1990s and early 2000s, suggesting that resources may have become limiting for this population. Here, we fit a Cormack-Jolly-Seber model to the resighting history of individually marked Grey Seals that have recruited to the Sable Island breeding colony since 1978 to estimate age- and sexspecific adult survival. Of those initially marked, 562 males and 1728 females were resighted in the breeding colony between 1978 and 2016. Average adult survival was high (male=0.943, Standard Error (SE)=0.003; female=0.976, SE=0.001), but male Grey Seals had lower survival at all ages. Resighting probability has remained between 60 and 80% since the late 1980s. Males are more likely to be sighted in a breeding season than females. Only female Grey Seals with pups are regularly sighted on the breeding colony; thus, those females that skip breeding are unobservable (temporary emigration). A multi-state open robust design model was used to estimate the transition probabilities between breeding (observable) and non-breeding (unobservable) states for individually marked females that were observed on the colony from 1992 to 2016. The first-order Markov state-dependent transition model was preferred over random transition probabilities. Females that gave birth had, on average, an 85% chance of pupping in the following year. However, females that did not give birth had a 56% chance of giving birth in the following year, suggesting that female quality plays a role in breeding probability. Although breeding probability varied among years, there was no trend over time suggesting the average natality rate has not changed and is not contributing to the slowing of the rate of growth in pup production. [ABSTRACT FROM AUTHOR]