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Re: Blog post: New species of hammerhead discovered, what does it mean for shark conservation?


Trevor Kenchington <[log in to unmask]>


Scientific forum on fish and fisheries <[log in to unmask]>


Mon, 11 Nov 2013 11:21:04 -0400





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That's an interesting one, David.

The tree that you copied in your blog is one based on mtDNA and I am
never happy with that as a foundation for taxonomy because of the
oddities of maternal inheritance. However, a quick glance at the two
papers (Quattro et al. 2006, 2013) shows that S.gilberti is also
distinct in one nuclear genetic marker, while (admittedly narrow)
distinctions in morphological characteristics line up with the
genetic ones. It all took me back to work I did on the northwest
Atlantic sebastinids decades ago, where we had a similar degree of
distinction between barely-recognizable types. If it were me doing
the work, I'm not sure (after just a quick glance at the papers) that
I would have given the new hammerhead taxon specific (rather than sub-
specific) status but there's often some subjectivity in that choice
and it's for the author of the work to decide, not for the rest of us
to second-guess.

Cryptic species are not all that unusual, of course, but you are
right that they raise complications where ESA-listed species are
concerned. Maybe we should be even more worried about cryptic species
that would merit ESA listing if they were recognized, when the more-
abundant congener with which they are confused is not listed. Then
again, if cryptic species are not highly unusual, spatially (or
otherwise) structured intra-specific variation is (almost) universal
and much of what matters in biological conservation concerns intra-
specific units and not species. Even when we are dealing with highly-
abundant species, we need to be aware that there are components
within their population structure that are (comparatively) rare and
may be under more pressure than other components. (Widespread
ignorance on that point didn't do once-abundant Atlantic cod any
good, though how far it contributed to their decline is hard to say.)

For obvious reasons, we all end up discussing issues from a U.S.
perspective and part of the problem you face with a case like
S.gilberti is that U.S. law provides the sledgehammer of the ESA for
anything that qualifies as an "endangered" or "threatened" species or
"distinct population segment" but precious little protection for most
other organisms in federal marine waters. (Marine mammals have the
MMA, of course. Resource species and whatever can be classed as
essential habitat for the resources have the MSFCMA but, in practice,
that does little to limit non-fishing anthropogenic pressures,) There
has been plenty of ink spilt over just how far human economic
interests should be curtailed to prevent the extinction of something
like a snail darter but I, for one, do not doubt that sledgehammers
are needed when a species is in imminent danger of extinction. The
problem with a "sledgehammer or nothing" regime are at the boundary
line, where species that are not under any real threat of extinction
get squeezed under the ESA so that they can have some protection (at
the cost of drawing conservation resources away from more critical
cases) or population components (be they intra-specific or cryptic
species) do not receive DPS or "species" status and are left with
little legal protection at all.

It is not the place of a foreigner to tell the United States how to
write its laws but some of your concerns would be eased by more
comprehensive marine-conservation legislation or perhaps a third ESA
status ("population unit of some concern"?) that receives a degree of
protection without bludgeoning of any human who so much as interacts
with a single individual (reserving extreme measures for interactions
with those species which really are on their last legs). I don't,
however, advise anyone holding their breath while they wait for the
U.S. Congress to work on anything like that.

Trevor Kenchington

On 11-Nov-13, at 9:07 AM, David Shiffman wrote:

>> <> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <><
> Hello, all! As some of you may have heard, a new species of hammerhead
> shark was recently discovered in South Carolina. I interviewed the
> scientists involved in the discovery and wrote a blog post about
> what the
> new species means for the conservation of hammerhead sharks in the
> U.S.
> Please share the blog post with anyone you think would be
> interested, and
> please let me know if you have any questions. I encourage you to ask
> questions of the study authors in the comments section of the blog
> post.
> Sincerely,
> --
> *David Shiffman*
> *Ph.D. Student, Research Assistant,*
> Abess Center for Ecosystem Science and Policy <http://
> R.J. Dunlap Marine Conservation Program <>
> *e: *[log in to unmask] | *p: *412.915.2309
> *a: *4600 Rickenbacker Cswy, Miami, Florida, 33149
> *t: *@WhySharksMatter <!/WhySharksMatter> | *b:
> *Southern
> Fried Science Blog <>
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