Ageing bias and precision for deep-water snappers: evaluating nascent otolith preparation methods using novel multivariate comparisons among readers and growth parameter estimates

Wakefield, Corey B., O'Malley, Joseph M., Williams, Ashley J., Taylor, Brett M., Nichols, Ryan S., Halafihi, Tuikolongahau, Humphreys, Robert L., Kaltavara, Jeremie, Nichol, Simon J., and Newman, Stephen J. (2017) Ageing bias and precision for deep-water snappers: evaluating nascent otolith preparation methods using novel multivariate comparisons among readers and growth parameter estimates. ICES Journal of Marine Science, 74 (1). pp. 193-203.

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Tropical deep-water snappers (Etelinae) support valuable fisheries across the Indo-Pacific, with stock assessments reliant on age-based information in the absence of reliable catch and effort statistics. These long-lived species have been considered notoriously difficult to age. However, nascent developments in ageing protocols, particularly thinner transverse sections of otoliths (similar to 180-200 mu m), are providing improvements in growth zone clarity, interpretation and repeatability of annuli counts. At a recent international workshop, thin sectioned otoliths from three deep-water snappers were read under reflected light by eight fisheries scientists from across the Indo-Pacific, with various levels of fish-ageing experience. Precision and bias were assessed using traditional ageing precision metrics (index of average percent error, IAPE; and coefficient of variation, CV), and a novel approach using multivariate analyses (metric multidimensional scaling, mMDS) based on Euclidean dissimilarity among readers' counts and subsequent von Bertalanffy (vB) growth parameter estimates. Annuli counts between the primary reader and all other readers were within two for 80% of estimates, with uniform variation across a wide age range for Etelis carbunculus (intraclass correlation coefficient (ICC) = 0.924, n = 20, 3-25 annuli) and Etelis sp. (ICC = 0.933, n = 15, 2-27 annuli). In contrast, annuli counts for Pristipomoides filamentosus (n = 14, 4-49) were less precise (i.e. ICC = 0.835, 66% of counts within two of primary reader) with a bias toward greater variation in younger, pre-maturational life stages (<= 5 annuli). Traditionally accepted ageing precision (IAPE <= 5.5%, CV <= 7.6%) was achieved for each species, but was commensurate with reader experience. The multivariate mMDS ordination was more informative in identifying both distance (i.e. dissimilarity) and direction (i.e. form) of variations in annuli counts and vB growth parameter estimates among readers. The acceptable level of ageing precision and bias achieved among most readers indicated that deep-water snappers can be aged precisely when appropriate otolith preparation methods are used. This study contributes towards ageing protocols that can be used.

Item ID: 50741
Item Type: Article (Research - C1)
ISSN: 1054-3139
Keywords: Lutjanidae, Etelinae, thin transverse sections, sagittal, opaque zone counts, fish ageing error
Date Deposited: 20 Sep 2017 11:32
FoR Codes: 31 BIOLOGICAL SCIENCES > 3109 Zoology > 310914 Vertebrate biology @ 25%
31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310408 Life histories @ 25%
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300502 Aquaculture and fisheries stock assessment @ 50%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8302 Fisheries - Wild Caught > 830204 Wild Caught Fin Fish (excl. Tuna) @ 80%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 20%
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