CRD 01-17
Session
I: Crustaceans
| Shell
disease prevalence and severity in offshore American lobster
populations |
Session
I: Crustaceans
Abstract No. I-1
ORAL PRESENTATION
|
Diane Kapareiko,
Richard A. Robohm, John J. Ziskowski, George R. Sennefelder, and
Anthony Calabrese
NOAA/NMFS/NEFSC,
212 Rogers Ave., Milford, CT 06460-6490
During the period 1990-1992,
15,004 lobster from 146 commercial catches at nine offshore canyon
sites surrounding the 106-Mile Sewage-Sludge Disposal Site were examined
for signs of shell disease. Overall, 1,184 lobster (7.9%) had lesions. Females
were more affected by this condition than males. Shell-lesion occurrence
was independent of carapace length (CL), but strongly related to location
(proximity to the 106-Mile Dumpsite as well as to the 12-Mile Dumpsite). Data
collection for the shell-disease study included not only evaluation
of presence or absence of disease, but also measurements of lesion
size and carapace length. This was done in anticipation of developing
a method that would determine the percentage of total surface area
of each lobster affected by shell disease; this percentage is the basis
of a Disease Severity Index (DSI). An estimate of lobster surface
area could be derived mathematically from carapace length, for both
male and female lobster in our database, using the formula y = 1.1034
+ 1.9677 * log(CL). The percentage of surface area covered by shell
lesions, multiplied by 103, provides a DSI that may allow
better statistical correlations between mean disease severity and site
of lobster collection.
Regression Tree analysis
of this multi-variate database indicated that, unlike prevalence, the
most important variable affecting the DSI was carapace length. Overall,
DSI’s for smaller lobsters (CL < 95 mm), were significantly higher
(p < 0.02) than larger lobsters, regardless of sex or location. Small
females had significantly higher DSI’s (p < 0.04) than large females. Males
showed no significant differences when similarly compared. A complete
non-parametric regression analysis of our DSI in relation to proximity
to the 106-Mile Site, may indicate whether sewage sludge dumping had
any effect on the severity of shell disease lesions in offshore American
lobster populations.
|
Reassessing
biodiversity estimates for decapod crustaceans off the eastern
United States: the importance
of new Species discoveries, improved taxonomy
and new phylogenetic hypotheses |
Session
I: Crustaceans
Abstract No. I-2
ORAL PRESENTATION |
Martha S.
Nizinski
NOAA/NMFS, National Systematics Laboratory, National Museum of
Natural History, Washington, DC 20560-0153
The decapod crustacean fauna
inhabiting estuarine, neritic, and continental shelf waters off the
east coast of the United States (Maine to central Florida) is rich
and diverse. Although seemingly well known, decapod faunal composition
and taxonomy in this region continues to change. The decapod fauna
off the eastern United States now comprises 366 species of which 65%
are crabs, 30% shrimps, 3% thalassinids, and 2% lobsters. Ten species
new to science have been discovered since 1982, when the last comprehensive
review of the decapod fauna from this region was completed. Thirty-two
species have either been reassigned to different genera (15 of which
are newly described) or placed in synonymy. Sixteen higher level taxonomic
changes (new superfamily, family, and subfamily designations; elevation
of subfamilies and subgenera to families and genera, respectively)
have also taken place. New methods, access to new material, and recent
investigations into higher level systematics provide the foundation
for better understanding of evolutionary relationships and constructing
more meaningful hypotheses to address questions, not only in the field
of systematics, but also those in comparative biology.
| Environmental
Monitors on Lobster Traps |
Session
I: Crustaceans
Abstract No. I-3
ORAL PRESENTATION |
James Manning
NOAA/NMFS/NEFSC, 166 Water St., Woods Hole, MA 02543-1026
The NOAA-funded "Northeast
Consortium" provides support to the fishing industry to conduct
collaborative research with scientist. The Environmental Monitors
on Lobster Traps (eMOLT) is one such project. Phase I, beginning
in year 2000, distributed temperature probes to over 50 New England
lobstermen represented by four associations (Atlantic Offshore, Mass,
Maine, and Downeast). These small (~3cm) instruments cost
less than $100, internally record hourly temperatures with an accuracy
of less than 0.1°C, and last for several years. They are deployed
for multiple months at fixed locations distributed throughout the Gulf
of Maine from the canyons on the southern side of Georges Bank to
the mouth of the St. John River. Phase II, this year, provides
a set of 9 Seabirds for monitoring salinity changes as well. The objective
will be to occupy the same locations annually to obtain an index of
both large-scale/long-term variability as well as a means of potentially
tracking pockets of water mass that advect through the region. Phase
III, next year, calls for setting up a series of computer stations/data
management centers along the coast to help participants in downloading
and documenting their deployments. Understanding the biological significance
of the physical variability will be a secondary (but potentially
worthwhile) byproduct of the results and one that the participating
lobstermen enthusiastically await. Details are posted on the project
website http://www.nefsc.nmfs.gov/~jmanning/emolt.html,
including links to, for example, "Results from the Field," "Data
Access," and much more.
Keywords:
temperature, lobster, environmental monitoring
|
Attack
and avoidance behavior between large and small blue crabs, Callinectes
sapidus, in the laboratory |
Session
I: Crustaceans
Abstract No. I-4
ORAL PRESENTATION |
Linda L.
Stehlik and Carol J. Meise
NOAA/NMFS/NEFSC, 74 Magruder Rd., Highlands, NJ 07732
Cannibalism by large blue
crabs is a well-recognized source of mortality of juveniles of the
same species. We initially determined the probability of being cannibalized
with a series of experiments in 2.3 and 0.9 mm diameter tanks, pairing
one adult crab >120 mm carapace width with a juvenile from one of
the size classes ranging from 20-29 mm to 100-109 mm CW. At size classes > 50-59
mm, prey crabs were almost never eaten.
Experiments were then conducted
in 0.9 m diameter tanks to determine the mechanisms of attack and avoidance. After
releasing the predators, the arenas were videotaped for 24 hr. Predator
crabs exhibited behaviors such as inspect, stalk, chase while swimming,
lunge with one chela outstretched, corral, consume, or maintain distance
if the prey crab was large. Prey crabs used swimming escape, maintaining
distance, autotomy, and burial to avoid capture. Prey 20-39 mm could
bury completely in the sand, and if they did so before the predator
detected them, they were never attacked. If they did not bury, they
were usually consumed. Some stood behind the central standpipe where
they were hard to see, and it was awkward for a large crab to reach
around with its chelae.
Several field studies of
blue crab vulnerability to predation have used tethering to keep the
prey in one location. Tethering is controversial because in some studies,
the tether causes unusual behavior, such as entanglement or inability
to bury. Our predation rates were lower than those from laboratory
studies with tethered crabs, although the maximum size of vulnerability
remained similar.
