posted on September 13, 2022 09:41
J. Northw. Atl. Fish. Sci., Vol. 53: 47–56
Publication (Upload) date: 13 Sep. 2022
Robertson, M.D.1*,Regular, P.M.2, and Cadigan, N.1
1Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland,
P.O. Box 4920, St. John’s, NL, A1C 5R3, Canada.
2Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, P.O. Box 5667
80 East White Hills Rd., St. John’s, NL, A1C 5X1, Canada.
*Corresponding author. Email: email@example.com
Robertson, M.D., Regular, P.M., and Cadigan, N. 2022. Limited temporal variability in natural mortality for juvenile American plaice on the Grand Bank of Newfoundland. J. Northw. Atl. Fish. Sci., 53: 47–56. https://doi.org/10.2960/J.v53.m738
Increases in natural mortality have been suggested as a potential driver for both the collapse and lack of recovery for the American plaice (Hippoglossoides platessoides) population on the Grand Bank of Newfoundland in NAFO Divisions 3LNO. However, natural mortality is among the most difficult parameters to estimate since it can be confounded with other parameters and model misspecifications. One method used to avoid this confounding involves modeling unfished components of a population where total mortality and natural mortality are equal. Here, we use a state-space metapopulation dynamics model to investigate whether there is evidence that natural mortality rates for unfished juvenile American plaice have varied since the population collapse. In addition, our model examined the degree of synchrony in age-1 recruitment signals between each management Division. The best fitting model included temporal variability in natural mortality rates, but estimates did not frequently differ from zero. This indicates that change in natural mortality rates is not an important driver of current juvenile 3LNO American plaice stock dynamics. Instead, this model identified that juvenile stock dynamics were mainly affected by variations in age-1 recruitment. Furthermore, a correlation analysis of the temporal variations in recruitment showed that trends were somewhat dissimilar between NAFO Divisions 3L and 3NO. Overall, although increases in M have been suggested by recent studies, we did not find strong evidence for this in juvenile fish.
Keywords: cohort dynamics, population dynamics, recruitment, spatiotemporal, state-space models
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: Robertson, M.D., Regular, P.M., and Cadigan, N. 2022. Limited temporal variability in natural mortality for juvenile American plaice on the Grand Bank of Newfoundland. J. Northw. Atl. Fish. Sci., 53: 47–56. https://doi.org/10.2960/J.v53.m738