Stone Crab 101

 

 

 

 

 

 

 

 

 

 

 

 

With the stone crab processing plant and aquaculture facility proposed
for Abaco, it is worth spending some time thinking about the viability of such
an endeavor in the context of stone crab biology.

Initial plans suggest the project will have three phases.   The first is a
direct stone crab fishery, and the second  is housing stone crabs, and repeatedly
harvesting their claws, at the proposed processing facility.  The success of these
two efforts hinges on two factors:  (1) availability of of stone crabs in Bahamian
waters, and (2) the space needed to raise stone crabs in captivity.  Lets take
each in turn.

The simple fact is that stone crab densities in The Bahamas are not high enough
to support a full scale commercial fishery operation.  Quoting from the FAO
report on aquaculture in The Bahamas (scroll down to section B for the stone
crab information): “It has a high market demand, but unlike the crawfish it is far
from abundant here”.  The basic literature suggests that stone crab densities
may be 1% or less compared to those in Florida.  This difference in density may
have many explanations.  First, Florida’s coastal waters are much more
productive in general, which may affect stone crab population sizes.  Or
perhaps the freshwater input in Florida’s coastal estuaries is critical for stone
crab life history.  Whatever the reasons, stone crabs are simply not very
abundant around Abaco.

If I am not mistaken, I think the initial plans were to bring 30,000 live
crabs into the rearing facility!   That alone would have a drastic impact on the
local population.  But even if there are sufficient population sizes for to support
captive crab raising, there is little likelihood that the facility will be able to
support the endeavor.  The NOAA website on stone crabs identifies this problem
succinctly:

“The most recent attempts at mariculture show that major hurdles, such as large
space requirements and the aggressive nature of the animal, must be overcome
before commercial production of stone crab is successful.”

Is there any indication that the owners of the processing facility  have the
experience or expertise to overcome a hurdle that professional aquaculture
companies have not been able to clear?  I think that question is rhetorical.

The third component of the project is apparently an attempt at full aquaculture
of the species.  That is, actually having captive breeding crabs and raising the spawned
larvae to reproductive adults.  This is a critical part of selling the processing plant
proposal to the government, as it is being characterized as a way that stone crab
the company will actually supplement, and thus increase, the natural stone crab
harvest. The chances of this component of the project working is just about zero.  To
understand why, a quick look at stone crab reproductive biology.

I copy some text here straight from the NOAA website on stone crab fisheries:

Stone crabs mate after molting when the female is soft. Males deposit
spermatozoa in the receptacle of the female. Eggs are fertilized within the ovary
lumen. After fertilization and ovarian development, eggs are deposited in an
external mass or sponge (160,000 to 1 million per egg mass) beneath the female
abdomen. At this time, females are termed ovigerous, or egg-bearing. Eggs
usually hatch within two weeks after they are extruded. Larval development
takes approximately four weeks before metamorphosis to the juvenile form.

The key here is the last sentence.  Stone crabs, like many marine invertebrates,
have a pelagic larval stage, meaning that the larvae are free-swimming
zooplankton that may waft on currents for weeks.  There is tremendous difficulty
in having a facility that can support raising these larval stage crabs.  As an
example, look at the complexities of blue crab rearing facilities.  This level of
expertise and commitment is far beyond that in the proposed Abaco project.

In sum, the current plan for a stone crab processing industry on Abaco is either
naive or insincere (or both).  Another boondoggle where environmental
damage likely will far exceed the purported benefits.  This and similar plans need
to be thoroughly vetted before they are allowed to go forward.

By | 2017-12-01T14:05:44-04:00 October 23rd, 2011|Categories: Current Events, Invertebrates, Policy|Tags: |4 Comments

About the Author:

Craig Layman
My lab’s interdisciplinary pursuits provide for a multi-faceted understanding of environmental change in the coastal realm. We are ecologists, asking questions that span population, community, ecosystem and evolutionary sub-disciplines. We often use a food web based perspective, exploring top-down (e.g., predation) and bottom-up (e.g., nutrient excretion) mechanisms by which animals affect ecosystem processes. All of our efforts are framed within a broader outreach framework, directly integrating science and education, using approaches such as this website.

4 Comments

  1. Avatar
    Janene Roessler January 28, 2012 at 11:08 am

    Hello, Craig. I met you at the Abaco Science Alliance conference. I came upon this post about Stone Crabs while searchiing for any info/research on your site about Hermit Crabs. I was doing some path clearing on our lot in Bahama Palm Shores and saw literally hundreds of Hermit crabs and began wondering about them. Anyhow, my question is: where in Abaco is this Stone Crab processing proposed, and who is proposing it?

    Couldn’t find any research gong on about hermit crabs. I found a hermit crab living in a pvc pipe elbow. The poor thing must have spent some time in my husband’s shop. :)

    Janene

  2. Avatar
    Janene Roessler January 28, 2012 at 11:10 am

    Where is this being proposed on Abaco? Who is proposing it?

    I met you at the Abaco Science Alliance conference. Was looking for any info on hermit crabs and stumbled upon this post.

    Janene

  3. laymanc
    laymanc January 29, 2012 at 2:04 pm

    Just north of Marsh Harbour on the west side. It will be right at the edge of the Marls. I dont remember their names offhand, but this is a partnership between a gentleman from Abaco, and two from the U.S.

  4. Avatar
    Catherine Stewart May 15, 2013 at 7:33 am

    I am a third grade science teacher at Coconut Grove Elementary in Miami, would there be any interest on your part in blogging or skyping with my students about marine life and the work of a scientist?

    Thank you.

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