[NatureNS] Horseshoe crabs here in Nova Scotia?

Date: Thu, 14 Feb 2008 14:37:17 -0400
From: "Andrew Hebda" <HEBDAAJ@gov.ns.ca>
To: <naturens@chebucto.ns.ca>
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&gt;&gt;&gt;&gt; 
Horseshoe crabs have appeared, several times in the last several decades, although it is not clear as to how often they were (accidentally) introduced.  We have a couple of records where they probably made it up on their own, but the latest report from Shelburne Harbour, several years ago ( I think)  appears to have been an illicit dump.  DFO should have a report on the occurrence.

Andrew 



>>> "Elizabeth Doull" <edoull@ns.sympatico.ca> 2/14/2008 2:10:03 pm >>>
I recall seeing some horseshoe crabs here in Nova Scotia when I was a kid. 
I haven't seen one for years so are they extinct or not in this province?

Thanks   Liz
----- Original Message ----- 
From: "Roland McCormick" <roland.mccormick@ns.sympatico.ca>
To: <naturens@chebucto.ns.ca>
Sent: Thursday, February 14, 2008 1:41 PM
Subject: Re: [NatureNS] Why save the Red Knot? - vertebrate hegemony?


>I read in the paper recently that one of the boys I taught in school was 
>fined a couple of thousand dollars for using crabs as bait to catch 
>lobster. I wondered about that at the time because I had never heard about 
>using them for bait before, or the reason for the fine.  I assume that is 
>what we are talking about here, and that there is a good reason for it.  I 
>can assure you that if this is true the fines are a good deal more than 
>$25.
>
> Roland.
> ----- Original Message ----- 
> From: "Paul S. Boyer" <psboyer@eastlink.ca>
> To: <naturens@chebucto.ns.ca>
> Sent: Thursday, February 14, 2008 11:26 AM
> Subject: Re: [NatureNS] Why save the Red Knot? - vertebrate hegemony?
>
>
>> The horseshoe crab is a living fossil, virtually unchanged since the 
>> Jurassic Period (in the middle of the Age of Reptiles).  Tracks of 
>> spawning horseshoe crabs have been found in Devonian rocks of 
>> Pennsylvania, which are far, far older.  Fossil relatives are found  in 
>> Manitoba from the Ordovician Period, about 445 MY old.
>>
>> There are only a few species of horseshoe crabs in the world (the 
>> American one, the subject of the program, and three minor Asian 
>> species). The American horseshoe crab is the largest and the most 
>> numerous, and the most spectacular to watch. New Jersey is the center 
>> for their abundance and average size, or at least it used to be.
>>
>> It is not the medical use that threatens the population, but the 
>> wasteful and (IMHO) lunatic use of horseshoe crabs as bait, or even 
>> fertilizer.  I have not checked recently, but when last I looked an 
>> annual license to take unlimited numbers of horseshoe crabs (seized  from 
>> the beaches while they are trying to spawn) was a mere $25.   Horseshoe 
>> crabs have a long lifespan, and do not recover quickly from  the 
>> depredation of being hauled away in truckloads.  Actually, the  Red Knot 
>> probably can increase its numbers faster with environmental  change than 
>> can the horseshoe crab, because the generation time is  shorter for the 
>> Knots.
>>
>> On 14 Feb 2008, at 2:04 AM, Stephen Shaw wrote:
>>
>>> Unfortunately missed the program, but I had a mild comment on the 
>>> species-ist
>>> emphasis here (sent it earlier but it didn't do through).
>>>
>>> Nothing against the Red Knot and of course I hope it survives, but  the 
>>> received
>>> vertebratocentric perspective on this is interesting.  As the blurb 
>>> below
>>> states,
>>> there are lots of other similar peep species around, but the  horseshoe 
>>> "crab"
>>> Limulus polyphemus is a unique species here and has been  practically 
>>> wiped out
>>> in many of its former habitats on the US East coast, according to  Bob 
>>> Barlow, a
>>> former student of Hartline (see below) who still works on it,  latterly 
>>> on its
>>> visual behaviour under water. Apparently the market for its blood  is 
>>> the main
>>> reason for the punitive "harvesting".
>>>
>>>  Besides having a far more interesting, ancient lineage, Limulus has
>>> contributed to several outstanding scientific discoveries in vision 
>>> science,
>>> notably that of "lateral inhibition" by which the nervous system 
>>> sharpens up
>>> percepts, enhancing edge-detection in images.  This has emerged as a
>>> common enhancing operation elsewhere in nervous systems, but  originally 
>>> came
>>> mainly out of work on the compound eyes of Limulus in the 40s-60s  --  
>>> netting a
>>> Nobel prize for H.K. Hartline, of the then Rockefeller Inst (now  Univ). 
>>> In the
>>> 60s, S. Yeandle made the first recordings of single photon captures  in 
>>> the same
>>> eye (since then recorded in vertebrates, though not in Red Knots), 
>>> while in the
>>> 70's, the first detailed analyses of how photoreceptor currents work
>>> (semi-universal) came out of measurements on huge photoreceptor  cells 
>>> in the
>>> ventral nerve that had been thought before this to be an olfactory 
>>> structure
>>> (analysed since in vertebrates, though not in Red Knots).   Circadian 
>>> rhythm
>>> mechanisms are big news at present (molecular mechanisms), and one  of 
>>> the best
>>> analyses of the circadian control of an eye by the brain came from 
>>> Barlow and
>>> colleague's work on the Limulus lateral eyes.  There are at least  two 
>>> other
>>> sets of eyes in horseshoe crabs, one UV sensitive and one in the 
>>> telson...
>>>
>>> None of these conceptual advances were minor cul-de-sacs and all  have 
>>> become
>>> incorporated into the neuroscience base, ever expanding. Limulus 
>>> deserves great
>>> respect as a unique and unusual pioneer invertebrate animal that  ought 
>>> to
>>> survive.  What has the Red Knot done to gain comparable respect?
>>>
>>> So, if I had to curry up votes for one of the two endangered  species, 
>>> it would
>>> be for the unique and illustrious horseshoe crab, first.  "Why save  the 
>>> Red
>>> Knot?" indeed -- do it second.
>>> Steve
>>> ******************************************
>>>
>>>
>>> Quoting Elizabeth Doull <edoull@ns.sympatico.ca>:
>>>> Why save the Red Knot?
>>>> PBS
>>>> flocks of shorebirds, the red knot is fairly average looking. In  fact, 
>>>> only the most practiced bird watchers may be able to  distinguish this 
>>>> medium-sized, plump peep from the thousands of  other shorebirds 
>>>> playing tag with the waves. Yet, somehow the red  knot has caught the 
>>>> attention of people around the world.
>>>>
>>>> The knot's dependence on the eggs of the heavily harvested  horseshoe 
>>>> crab has placed it at odds with another species --  humans. 
>>>> Conservation groups, lawmakers, fishermen, scientists, and  ordinary 
>>>> citizens have all entered the debate. But even as our  actions have 
>>>> imperiled the red knot, we can also preserve the  species, by 
>>>> regulating the fishing industry and keeping clear of  the beaches that 
>>>> the knots rely on during migration. Where nature  ranks in our system 
>>>> of values will dictate how far we are willing  to go to protect the red 
>>>> knot.
>>>>
>>>> There are millions of shorebirds in the world. Why all the clamor  over 
>>>> the red knot? How could this small bird stir up so much  controversy 
>>>> and inspire such extraordinary efforts on its behalf?  To begin to 
>>>> answer these difficult questions we must first become  familiar with 
>>>> the red knot.
>>>>
>>>> The red knot may blend in with the other small shorebirds, but it 
>>>> makes a journey that certainly sets it apart. A master of long- 
>>>> distance aviation, the red knot makes one of the longest migratory 
>>>> trips of any bird -- 9,300 miles along the Atlantic flyway from  its 
>>>> wintering grounds in southern South America to its high Arctic 
>>>> breeding grounds. The journey is so exhausting, it requires two to 
>>>> three stopovers for refueling. The horseshoe crab egg feast they  will 
>>>> consume at Delaware Bay, is not just an indulgence -- it's  absolutely 
>>>> crucial for the birds' survival. When the knots arrive  at Delaware 
>>>> Bay, their bodies are half their starting weight,  devoid of fat and 
>>>> even some muscle. Here, the red knot will take  about two weeks to 
>>>> double its weight so it can continue its  migration.
>>>>
>>>> The migratory trip is far from the only risk the peeps take in  their 
>>>> lives. The life of the red knot is fraught with challenges.  In their 
>>>> wintering grounds of Tierra del Fuego, blinding gales  blow up without 
>>>> warning, and tides surge 25 and 35 feet every 12  hours. The challenges 
>>>> facing the knots are even greater on the  Arctic nesting grounds, where 
>>>> a declining population of birds  makes it more difficult to find a mate 
>>>> and even if they do, a  snowstorm can wipe out the knots' eggs. If the 
>>>> birds don't consume  enough eggs during their migratory stopover, they 
>>>> may not have  enough fuel to complete their trip, and those 
>>>> undernourished knots  that do make it to the Arctic will arrive weak 
>>>> and emaciated. Add  the fierce and unpredictable Arctic weather into 
>>>> the mix, and the  birds are likely to be in such a state that it is 
>>>> nearly impossible for them to raise chicks.
>>>>
>>>> Researchers tag red knots in 'Crash: A Tale of Two  Species.'Nature, it 
>>>> seems, has really stacked the deck against  this creature. During its 
>>>> migration, the red knot concentrates in  huge, densely-packed flocks. 
>>>> These enormous gatherings make the  knots vulnerable to habitat 
>>>> destruction and, in South America,  hunting pressure. Sadly, it is not 
>>>> just their eating preferences  but their social patterns that put them 
>>>> at odds with human  activities.
>>>>
>>>> All of these hardships have given rise to dire statistics. The red 
>>>> knot is a creature in peril. The U.S. Shorebird Conservation Plan 
>>>> lists the red knot as a "Species of High Concern," based on  declining 
>>>> population trends and threats on non-breeding grounds.  In the last 20 
>>>> years red knots have declined from over 100,000 to  less than 15,000. 
>>>> And in 2006, the knot was named a candidate for  Endangered Species Act 
>>>> protection as an emergency measure to slow  the rapid fall of its 
>>>> population. In the Delaware Bay, the knot  has suffered a decline so 
>>>> severe that some experts predict the  population stopping over at the 
>>>> bay could disappear within five  years.
>>>>
>>>> Studies conducted outside of the U.S. do not paint a brighter  picture. 
>>>> Counts of knot populations wintering in South America  dropped over 50% 
>>>> from the mid-1980s to 2003. Researchers have  suggested that the 
>>>> continued hunting of knots in South America  might be partly to blame.
>>>>
>>>> The red knot is one of the world's most amazing birds. But if that  is 
>>>> not sufficient motivation for us to save it, there are other 
>>>> incentives. Chincoteague, Virginia, a popular stop-over for the  red 
>>>> knot, finds that what is good for migratory shorebirds is also  good 
>>>> for Virginia business. A recent tourism survey found that  birders and 
>>>> ecotourists were bringing in significant amounts of  resources to the 
>>>> local economy. And one economic study in South  Jersey found that the 
>>>> shorebird-watching industry generated nearly  $36 million dollars in 
>>>> revenue for the area.
>>>>
>>>> Sadly, the issue raised in "Crash: A Tale of Two Species" over the 
>>>> increased harvest of horseshoe crabs remains contentious today. 
>>>> Whether the red knot will be able to continue to use Delaware Bay  as a 
>>>> major migratory staging area in the future is still up in the  air --  
>>>> as is the fate of the knot.
>>>>
>>>> For more information on red knot conservation efforts, visit 
>>>> http://shorebirdproject.blogspot.com/, where Larry Niles (featured  in 
>>>> "Crash: A Tale of Two Species") and an international team of 
>>>> scientists blog about the most recent news on the red knot.
>>>
>>
>>
>> -- 
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