[MARMAM] New publication on the morphometric discrimination of Hawaiian blackfish species (Shelby Yahn)

Shelby Yahn shelby.yahn at gmail.com
Thu Jan 31 11:45:12 PST 2019

Dear colleagues,

We are pleased to announce the publication of our article, which is now
available online:

Yahn, S. N., R. W. Baird, S. D. Mahaffy and D. L. Webster. 2019. How to
tell them apart? Discriminating tropical blackfish species using fin and
body measurements from photographs taken at sea. Marine Mammal Science.
DOI: 10.1111/mms.12584.


The misidentification of species and populations is a hindrance to
effective cetacean management. We devised a method of species
identification using 10 fin and body measurements obtainable from at-sea
photographs, and demonstrated its ability to distinguish four species of
Hawaiian “blackfish”: pygmy killer, melon-headed, short-finned pilot, and
false killer whales. Measurements from photos of 382 known individuals were
converted into 14 ratios and reduced using nonmetric multidimensional
scaling and principal component analysis. The first three components of the
PCA explained 81% of variance among species. Ratios indicated by PCA and
NMDS were tested using analysis of variance, and results identified three
fin ratios that had distinct means across all four species: height/base,
depth (from anterior insertion) at trailing edge apex/depth at topmost
point, and width (from leading edge) at posterior point/base. Dual analysis
of adults and all age classes showed near-identical sources of variance,
90% similarity in interspecies ratio relationships, and overlapping ratio
means and ranges. Results suggest similar ontogenetic growth across these
four species, and confirm the efficacy of this discrimination technique for
all age classes. This study established a reliable means of distinguishing
these cetacean species, which will improve the efficacy of management in
areas with sympatric distributions.

Please feel free to send any questions or comments concerning the article
to me at Shelby.Yahn at gmail.com

Best of wishes,

Shelby and co-authors
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