Natural mortality estimators for information-limited fisheries
Article first published online: 6 APR 2013
© Her Majesty the Queen in Right of Canada 2013. Reproduced with the permission of the Minister of Department of Fisheries & Oceans.
Fish and Fisheries
Volume 15, Issue 4, pages 533–562, December 2014
How to Cite
Kenchington, T. J. (2014), Natural mortality estimators for information-limited fisheries. Fish and Fisheries, 15: 533–562. doi: 10.1111/faf.12027
- Issue published online: 23 OCT 2014
- Article first published online: 6 APR 2013
- Manuscript Accepted: 25 JAN 2013
- Manuscript Received: 10 AUG 2012
- Gulf and South Atlantic Fisheries Foundation, Inc.. Grant Number: NA04NMF4520280
- Information-limited fisheries;
- natural mortality
The 29 estimators of natural mortality (M) that have been proposed for ‘information-limited’ fisheries are reviewed, together with a new alternative presented here. Each is applied to 13 example populations for which well-founded estimates are available of both M and the estimators' parameters. None of the 30 can provide accurate estimates for every species, and none appears sufficiently precise for use in analytical stock assessments, while several perform so poorly as to have no practical utility. If the growth coefficient K has been reliably estimated, either M = 1.5 K or Pauly's long-established estimator can provide useful estimates of M, but they fail with species that have long adult lives after swift juvenile growth, with those that never reach their asymptotic lengths and with species that otherwise deviate from archetypal teleost life histories. If a pre-exploitation maximum observed age (Tmax) can be established, M can be estimated for both teleosts and sharks using M = 4.3/Tmax but that seriously underestimates when the effective sample size (ne) is large and overestimates with species showing pronounced senescence. The new estimator presented here addresses ne but is upset by even mild senescence. Some estimators of M-at-size, particularly ones recently advanced by Gislason et al. and Charnov et al., also show promise but require further examination. It is recommended that fisheries scientists measure M by more advanced methods whenever possible. If ‘information-limited’ estimators must be used, their uncertainties should be acknowledged and their errors propagated into management advice.