[MARMAM] New article

Phillip Clapham - NOAA Federal phillip.clapham at noaa.gov
Tue Apr 24 04:49:57 PDT 2018


The following was just published:

Clapham, P.J. & Ivashchenko, Y.V.  2018.  Whaling catch data are not
reliable for analyzing body size shifts.  Nature Ecology and Evolution doi
10.1038/s41559-018-0534-2.

This is a short rebuttal to a paper published by Clements *et al.* in
2017.  There is no abstract, but the entire text is pasted in below.  A pdf
is available fo anyone unable to access the *Nature* site.

--
Phillip J. Clapham, Ph.D.
Leader, Cetacean Assessment and Ecology Program
Marine Mammal Laboratory
Alaska Fisheries Science Center
7600 Sand Point Way NE
Seattle, WA 98115, USA

tel 206 526 4037
email phillip.clapham at noaa.gov


*Whaling catch data are not reliable for analyzing body size shifts*

Clements *et al. *(1) use length data from the International Whaling
Commission’s (IWC) catch database to support their contention that a
negative shift in body size reflects an “early warning signal” prior to the
collapse of stocks of blue, fin, sei and sperm whales.
   There are several problems with this analysis.  First, length data for
sperm whales were extensively falsified by both Japan and the USSR.  The
USSR conducted extensive illegal whaling beginning in 1948 (2), and
submitted falsified data on both the length and sex of sperm whales to
cover up extensive catches of animals below the minimum legal length
(11.6m) (3).  Clements *et al. *mention the absence of length data for
Soviet Southern Hemisphere catches, but not for the North Pacific.  This
presumably means that they used the falsified North Pacific data, which
were only recently replaced (without lengths) in the IWC database (4).
Similarly, it is now known that, for the same reason, Japan routinely
falsified data on the lengths and sexes of sperm whales in shore-based
whaling operations in the North Pacific (5), and on lengths for pelagic
factory fleets there and throughout the Southern Hemisphere (6,7).
   Consequently, any analysis of sperm whales will be fatally flawed: using
changes in the 95% mean size does not help when the data concerned are
largely fabricated.  The Clements *et al. *analysis also failed to account
for the age- and sex-segregated nature of sperm whale distribution, in
which catches in high latitudes were primarily of large males while those
elsewhere were biased towards the much smaller females and juveniles.
Consequently, the shift over time in Southern Hemisphere whaling effort
from the ice edge northwards would have resulted in increasing proportions
of smaller animals in the catch (even if length and sex were accurately
reported).
   Another problem relates to Southern Hemisphere blue whales.  In the
early 1960's, catches shifted from “true” blue whales in high latitudes to
the significantly smaller pygmy subspecies (*B. musculus brevicauda*) (8,
9), yet the authors did not account for this in their analysis.
Furthermore, the reported shift in length for Antarctic blue whales
occurred after populations had collapsed to 1% of their former abundance in
1960 (8); thus, a decline in length should have been apparent well before
this point.
   Any as-yet unknown falsifications for other species will further
complicate such analyses.  A recent study suggested that, with some
exceptions, length data reported by Japanese whalers for catches of
Southern Hemisphere fin whales are probably largely reliable (10).  To
date, no one has conducted such an assessment for sei whales; however, the
USSR actually over-reported catch numbers for both fin and sei whales to
camouflage takes of other species (2), which means that some of the North
Pacific length data would have been from non-existent animals.
   It is indeed likely that over-exploitation of whale stocks resulted in a
decline in average lengths over time, and length data might be able to
identify signals of diminishing abundance.  However, this is valid only if
the length data are both reliable and correctly interpreted, and that is
not the case for at least two of the species here.

The authors thank Trevor Branch for his thoughtful review of this note.

Phillip J. Clapham* and Yulia V. Ivashchenko

Marine Mammal Laboratory, Alaska Fisheries Science Center, 7600 Sand Point
Way NE, Seattle WA 98115, USA
*Corresponding author.  Email: phillip.clapham at noaa.gov


References

    1. Clements, C.F. et al.  Nature Ecol. Evol. 1, 1-12 (2017).
    2. Ivashchenko, Y.V. & Clapham, P.J.  Mar. Fish. Rev. 76, 1-21 (2014).
    3. Ivashchenko, Y.V., Brownell, R.L. Jr. & Clapham, P.J.  End. Species
Res. 25, 249-263 (2014).
    4. Ivashchenko, Y.V., Brownell, R.L. Jr. & Clapham, P.J.  J. Cetacean
Res. Manage. 13, 59-71 (2013).
    5. Kasuya, T.  J. Cetacean Res. Manage. 1, 109-22 (1999).
    6. Ivashchenko, Y.V. & Clapham, P.J.  Royal Soc. Open Sci. 2, 150177.
DOI: 10.1098/rsos.150177 (2015).
    7. Clapham, P.J. & Ivashchenko, Y.V.  Royal Soc. Open Sci. 3, 160506
DOI: 10.1098/rsos.160506 (2016).
    8. Branch, T.A., Matsuoka, K. & Miyashita, T.  Mar. Mammal Sci. 20,
726-754 (2004).
    9. Branch, T. A.  J. Cetacean Res. Manage. 9, 253–262 (2007).
    10. Clapham, P.J. & Ivashchenko, Y.V.  Paper SC/67a/IA1 available from
the International Whaling Commission (2017).
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