Fisheries Research Articles

Evaluating the performance of otolith morphometrics in deriving age compositions and mortality rates for assessment of data-poor tropical fisheries

Document Type

Article

Publication Date

3-15-2015

Journal Title

ICES Journal of Marine Science

ISSN

Print: 1054-3139 Electronic: 1095-9289

Keywords

Age, Biological indicators, Deepwater snapper, Etelis, Mortality, Otolith morphometrics, Pacific Ocean, Pristipomoides, Random forest, Reference points

Disciplines

Aquaculture and Fisheries | Marine Biology | Natural Resources and Conservation | Natural Resources Management and Policy | Sustainability

Abstract

Deepwater snappers (Family Lutjanidae) are important to artisanal and subsistence fisheries in Pacific Island countries. Most species of deepwater snapper are considered vulnerable to exploitation due to their extended longevity and low natural mortality rates. However, the sustainability of deepwater snapper fisheries in Pacific Island countries remains uncertain because there are limited resources available to collect the required data for comprehensive stock assessments. Reliable estimates of the age composition for exploited deepwater snapper populations are limited primarily because of the lack of skills and resources required for routine age estimation from sectioned otoliths. The development of alternative low-cost approaches to derive estimates of age for deepwater snappers is required. We evaluated the performance of using otolith morphometrics (weight, length, width, and thickness) to obtain estimates of age for the most important target species in these fisheries: Etelis carbunculus, E. marshi, E. coruscans, and Pristipomoides filamentosus. We compared age compositions and fishing mortality rates (F) derived from otolith morphometrics with those derived from counts of annual increments in otoliths. We then used the ratio of F to natural mortality (M) as a biological indicator to evaluate the potential effects on management responses by comparing estimates of F/M derived from otolith morphometrics with those derived from annual increment counts. Age compositions and estimates of F and F/M did not differ significantly between those derived from otolith morphometrics and those derived from annual increment counts for all species. These results demonstrate that management responses would likely be similar whether based on age estimates derived from sectioned otoliths, or predicted from otolith morphometrics. In the absence of sufficient resources to section otoliths for age estimation, we recommend that otolith morphometrics be used as a proxy for age in assessments of deepwater snapper fisheries in Pacific Island countries, and potentially for other similar data-limited fisheries.

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Digital Object Identifier (DOI)

https://doi.org/10.1093/icesjms/fsv042