We evaluated relative
efficiencies of collection methods for epigean vs. burrowing crayfish. We found that the
most efficient method depended on the type of waterway and the specific habitat
preferences and behavior of each species.
Generally, in clear water with rocks or woody debris, it was fairly easy
to find crayfish by manually overturning or disturbing any shelter (rock or
woody debris), visually locating the crayfish, and catching it by hand or net. It was easier to see and catch crayfish
while snorkeling than with one’s head above water. It was also rather effective to swipe a dip net through
vegetation. In streams where there was
not much shelter available, finding crayfish proved more difficult. In tannic or turbid water, visual location
was often impossible or at least impeded, and blindly using dip nets (swiping
through vegetation or disturbing shelter) proved more effective. Electroshocking seemed to work well in
certain circumstances in both clear and tannic water, but was generally less
reliable than dip netting, and its effectiveness declined with visibility. Electroshocking worked well in riffles and
especially well in tannic systems during spring (presumably when crayfish are
out of burrows, looking for mates). Oftentimes,
burrow entrances were visible in stream banks.
Splashing and digging into these did not usually yield any crayfish,
whereas excavating in-stream burrows proved useful. Digging burrows in the floodplain was successful about half the
time, and ease depended on the type of soil present. Minnow traps often did not yield any crayfish, but usually a
successful trap held more than one individual.
This suggests that trap placement, rather than bait choice, is crucial
to its success. We have not yet used
enough Pitfall traps to determine their efficiency. Searching for crayfishes at
night was not usually employed (for the safety of field biologists) but should
be effective, because many species are active at night.
Surveys for crayfishes were
conducted by river basin, on the following schedule: Completed surveys: 1 May
through 30 November 2001: Savannah,
French Broad, and Lumber (including Waccamaw) River Basins. The remaining is a proposed timeline: 1 April through 31 October 2002: Broad, New, Neuse, and Tar-Pamlico River
Basins, 1 April 2002 through 31 October 2003: Hiwassee, Little Tennessee, Cape
Fear, Northeast Cape Fear, and White Oak River Basins; 1 April through 30 June
2004: Chowan and Roanoke River Basins.
Listed below are individual
accounts of completed surveys focusing on each of the species targeted during
this study. These accounts detail
abundances, size information, reproductive status, habitat preferences, species
associates, and any other relevant findings.
Additionally, we identify any threats (e.g., factors affecting water and
habitat quality) that we believe could negatively affect the stability of these
populations. To compare statistics
(e.g., population, stream miles, % impaired streams) among river basins in
North Carolina, visit this page
compiled by the NC Division of Water Quality.
We recorded the presence and
relative abundance of common crayfishes encountered during this survey. Information about these species is provided
as species associates of individual target species in those individual
accounts. A list of the species
considered common in North Carolina is as follows: Cambarus (Cambarus) bartonii (Fabricius 1798) (Appalachian
brook crayfish), C. (Depressicambarus) latimanus (LeConte 1856) (no
common name), C. (D.) reduncus Hobbs 1956 (no common name), C.
(Hiaticambarus) longirostris Faxon 1885 (no common name), C. (H.)
longulus Girard 1852 (no common name), C. (Jugicambarus) asperimanus Faxon
1914 (no common name), C. (J.) dubius Faxon 1884 (no common name), C.
(Lacunicambarus) diogenes Girard 1852 (no common name), C.
(Puncticambarus) robustus Girard 1852 (big river crayfish), C. (P.) sp.
C (a species complex related to C. acuminatus Faxon 1884), Fallicambarus
(Creaserinus) fodiens (Cottle 1863) (no common name), and Procambarus
(Ortmannicus) acutus (Girard 1852) (White River crayfish). We also recorded the presence of fishes and
aquatic mollusks in many cases (data available upon request). This is not an exhaustive list, as our
purpose was to survey for crayfishes, but may be useful particularly as
baseline data and as insight into health of waterways surveyed.
This species was observed at
10 of the 28 sites surveyed in the Savannah River
Basin (see associated map for sites surveyed), and abundance ranged
from 5.8 to 21.9 (mean + standard deviation: 11.5 + 5.8) animals
observed per person-hour of search time.
Typically, this species was found in flowing water, hiding under rocks,
with larger individuals under larger rocks, and usually only one crayfish per
rock (but 7 in one case). Sites where
it occurred tended to be medium to large streams, and it was not observed in
small tributaries. Species associates
included Cambarus asperimanus, C. bartonii, and C. reburrus. Cambarus asperimanus was by far the
most common of the other crayfishes, and was often found in similar habitat as
that apparently preferred by C. chaugaensis. At 2 sites, no species other
than Cambarus chaugaensis were observed. Of 122 individual C. chaugaensis observed, 116 were
measured (carapace length), and sizes ranged from 8.6 to 44.2 mm, with a mean +
standard deviation of 22.0 + 9.0 mm.
Reproduction was evident, as we observed 6 form I males, 2 females
in-berry, and juveniles were observed at 7 of the 10 sites where this species
occurred. It is possible that
individuals identified as C. chaugaensis may in fact belong to a member
of the C. bartonii species complex but it is our belief at this time
that we have assigned identifications as well as can be expected, given our
knowledge of the Savannah fauna.
Until recently, the North
Carolina portion of the Savannah River Basin has remained relatively
undeveloped and pristine. Currently,
the area seems to be developing at a higher rate than in the past, with tourist
attractions such as the towns of Highlands, Cashiers, and Sapphire, the newly
established Gorges State Park, and Lake Toxaway. Some timber cutting in the region may also affect habitat and
stream quality. Otherwise, due to the
steep and rocky nature of the landscape in this area, it is likely that these
streams will remain relatively high quality, so long as they are not further
dammed. See the Division of Water Quality’s
Savannah
River Basinwide Water Quality Plan, 1997 for information on land use,
population growth, and stream quality.
Because C. chaugaensis appears to be widespread and common in the
area, the population should remain healthy.
A potential threat to the population might be the introduction of
nonindigenous competitors.
This species was observed at
2 of the 28 sites surveyed in the Savannah River
Basin (see associated map for sites surveyed), and abundance ranged
from 1.6 to 2.0 (1 animal at 1 site, and 3 at a second site) animals observed
per person-hour of search time. At
these sites, this species was found in flowing water, hiding under rocks. Both places were medium-large rivers
(Horsepasture and Chatooga Rivers).
Species associates included Cambarus asperimanus, and C.
chaugaensis. Of the 4 individual C.
reburrus observed, all were measured (carapace length), and sizes ranged
from 24.2 to 33.5 mm, with a mean + standard deviation of 29.2 +
4.3 mm. Reproduction was not evident,
as all animals observed were non-reproductive adults. Although C. reburrus was described from the Savannah River
Basin, it is likely that it is not native there. See the discussion above (C. chaugaensis, 2nd
paragraph) for potential threats to stream species in the Savannah River Basin.
This species was observed at
10 of the 85 sites surveyed in the French Broad River
Basin (see associated map for sites surveyed), and abundance ranged
from 1.0 to 13.3 (mean + standard deviation: 4.6 + 4.3) animals
observed per person-hour of search time.
Typically, this species was found in slow flowing water (often at edges,
near banks), hiding in detritus (leaf packs, woody debris), or in vegetation,
generally in areas with silty substrate, but occasionally in faster flow under
rocks. Sites
where it occurred tended to be medium to large streams, and it was not observed
in small tributaries. This species was
only observed in the mainstem French Broad Subbasin, and not in the Pigeon or
Nolichucky Subbasins, which is consistent with previous observations. Species associates included Cambarus bartonii and C. robustus. No other species of crayfish occurring with C.
reburrus tended to inhabit similar habitat type. At 3 sites, no
species other than Cambarus reburrus were observed. Of 54 individual C. reburrus observed,
53 were measured (carapace length), and sizes ranged from 6.1 to 40.9 mm, with
a mean + standard deviation of 17.2 + 9.5 mm. Reproduction was evident at half of the
sites where this species occurred, indicated by the presence of juveniles.
The French Broad River Basin
has seen tremendous growth over the past several decades, particularly in areas
containing the largest cities. These
include: (1) mainstem French Broad Subbasin: Asheville (Buncombe County),
Hendersonville (Henderson County), Brevard (Transylvania County); (2) Pigeon
Subbasin: Canton and Waynesville (Haywood County); and (3) Nolichucky Subbasin:
Burnesville (Yancey County), and Spruce Pine (Mitchell County). Population is less dense in other areas but
much of the river basin is still highly developed with a large amount of
agriculture or timber harvest, and many streams have roads running alongside
with very narrow buffers. Land use
consists of approximately 17% agriculture (crop and pasture), 10% urban or
built-up, 24% “other”, and ~50% forested (as reported in the Division of Water
Quality’s French
Broad River Basinwide Water Quality Plan, 2000, based on data from
1992). The amount of land use in
agriculture has declined (~72%) whereas the amount of urban or built-up area
has increased (~42%) substantially since 1982.
Population is estimated to increase by approximately 15% overall in the
river basin by 2016 (from 1996 numbers; DWQ report). Streams falling into the designation as impaired (303-d list)
include: Peter Weaver Creek, Morgan
Mill Creek, Gash Creek, Mill Pond Creek, Mud Creek, Bat Fork Creek, Clear
Creek, Hominy and South Hominy Creeks, Ross Creek, Mills River, Brandy Branch,
Little Ivy Creek, Pigeon River, and Richland Creek. Several refuges exist where streams are protected: (1) Great
Smoky Mountains National Park (Haywood County), Mount Mitchell State Park
(Yancey County), and Pisgah National Forest and Game Lands (all counties, with
a particularly nice area in Transylvania County). Generally, areas at higher elevations appear to be less impacted
than the floodplain region around the mainstem French Broad River.
Although this survey was
less intensive than we would have liked due to time constraints, we noticed
some trends about the abundance and distribution of Cambarus reburrus
within the French Broad River Basin.
Compared to the estimated historical distribution (based on locations
reported from previous surveys), we believe that this species is less widely
distributed today. We are particularly
concerned with the Mills River, in which we found very few specimens but
historically supported an apparently widespread population. Also, in the increasingly degraded Swannanoa
River, we found very few individuals.
This species appears to prefer low-gradient, slow moving and large
streams and rivers. Thus, because most
of the waterways of this type occur in highly developed areas (protected areas
are mostly high-gradient), this species may be at risk due to habitat loss and
water quality impairment. The continued
presence of this species in these degraded waterways may provide hope that they
are able to contend with these changes.
However, despite our limited ability to calculate abundance comparisons
with historical data, this species appeared to be generally uncommon in streams
where we observed it during this study.
This species was observed at
4 of the 46 sites surveyed in the Lumber River Basin
(see associated map for sites surveyed), and abundance ranged from 1.2 to 19.4
(mean + standard deviation: 11.7 + 7.6) animals observed per
person-hour of search time. Typically,
this species was found in water with some degree of flow (usually light tannic),
hiding in vegetation, root wads, or woody debris. Sites where it occurred tended to be medium to large streams, and
it was not observed in small tributaries.
Species associates included Cambarus sp.C and Procambarus
blandingii (acutus). Of 24 individual P. braswelli observed, all were
measured (carapace length), and sizes ranged from 10.0 to 27.5 mm, with a mean +
standard deviation of 16.2 + 4.6 mm.
Reproduction was evident, indicated by the presence of 5 form I males
and juveniles at 3 of the 4 sites where this species occurred.
This species was observed at
4 of the 32 sites surveyed in the Waccamaw River
Basin (see associated map for sites surveyed), and abundance ranged
from 2.0 to 14.0 (mean + standard deviation: 9.0 + 6.2) animals
observed per person-hour of search time. Typically, this species was found in
water with some degree of flow (usually light tannic), hiding in vegetation,
root wads, or woody debris. Sites where
it occurred tended to be medium to large streams, and it was not observed in
small tributaries. Species associates
included Procambarus ancylus and Procambarus blandingii (acutus). At 2 sites (both Waccamaw River), no species
other than Procambarus braswelli were observed. Of 31 individual P. braswelli observed,
all were measured (carapace length), and sizes ranged from 7.0 to 24.8 mm, with
a mean + standard deviation of 13.0 + 4.4 mm. Reproduction was evident, indicated by the
presence of 2 form I males and juveniles at half of the sites where this
species occurred.
Land use in the Lumber River
Basin (including Little Pee Dee and Waccamaw Subbasins) consists of
approximately 59% forestland, 28% agriculture (crop and pasture), and 6% urban
or built-up (as reported in the Division of Water Quality’s Lumber
River Basinwide Water Quality Plan, 1999, based on data from 1992). The urban or built-up category increased by
49% since 1982, and agriculture decreased by about 24% during this time. Yet a substantial amount of agriculture or
timber cuts are scattered about the area, as are poultry and hog
industries. Population growth has been
slightly lower than the state average for most of the region but higher in
portions of Moore and Brunswick Counties and in the Lumberton area. Population growth is expected to increase by
around 45% by 2015 (from 1990 numbers; DWQ report). The largest metro areas in the river basin include Lumberton
(Robeson County), Laurinburg (Scotland County), Whiteville (Columbus County),
and several smaller towns scattered around, including the expanding developed
area extending southeast of Southern Pines.
Much of the past activities of wetland draining and ditching have had
significant impacts on the area’s fauna.
Due to new regulations and the wet nature of the area, much of the
swampland is now protected to some degree, especially the Green Swamp area near
Lake Waccamaw and the bottomland hardwood areas surrounding the major river
systems (Little Pee Dee system, Lumber River and Ashpole Swamp system, and
Waccamaw River system). Lake Waccamaw
and Lumber River State Parks also provide refugia for stream-dwelling
organisms. Many of these streams
sustain a high diversity of animals, many of which are endemic and some having
a very localized distribution.
Currently, no waterways in this river basin are listed as impaired
(303-d list). The largest threat to
animals associated with streams, swamps, and wetlands in the river basin seems
to be habitat loss due to increased development.
Based on known localities of
Procambarus braswelli, we believe the population continues to be stable
in its range within the Waccamaw River.
We also found multiple new locations in the Little Pee Dee Subbasin (Gum
Swamp and Shoe Heel Creeks), where it appears to be common, although patchily
distributed. We did not establish any
new locations in other parts of the river basin.
Of the 46 sites surveyed in
the Lumber River Basin (see associated
map for sites surveyed) during this study, this species was not observed. However, this species was observed during
previous recent surveys conducted by Nongame & Endangered Wildlife Program
personnel and colleagues, and the potential range map (this web atlas) reflects these
data.
This species was observed at
6 of the 32 sites surveyed in the Waccamaw River
Basin (see associated map for sites surveyed), and abundance ranged
from 1.3 to 14.0 (mean + standard deviation: 6.6 + 4.6) animals
observed per person-hour of search time.
Typically, this species was found hiding in vegetation, or woody debris,
or detritus. Sites where it occurred
tended to be small to medium-large streams, and flow varied from stagnant to
moderate gradient. Species associates
included Procambarus blandingii (acutus) and P. braswelli. Of 27 individual P. ancylus observed,
all were measured (carapace length), and sizes ranged from 7.2 to 21.5 mm, with
a mean + standard deviation of 13.3 + 4.1 mm. Reproduction was evident, indicated by the
presence of 1 form I male and juveniles at half of the sites where this species
occurred.
See the discussion above for
P. braswelli (penultimate paragraph) for potential threats to aquatic
species in the Lumber (and Waccamaw) River Basin.
We have yet to thoroughly
survey for this species in the Cape Fear (including
Northeast Cape Fear) River Basin.
Taxonomically distinguishing
between P. blandingii and P. acutus requires form I males;
therefore when we had only females or non-form I males, we labeled the
specimens as P. acutus/blandingii.
Here, we provide analyses separately.
Procambarus blandingii was observed at 29 of the
46 sites surveyed in the Lumber River Basin
(see associated map for sites surveyed), and abundance ranged from 1.9 to 54.5
(mean + standard deviation: 10.3 + 11.4) animals observed per
person-hour of search time. Procambarus acutus/blandingii was observed at 4 of
the 46 sites surveyed in the Lumber River Basin, and abundance ranged from 1.9
to 7.1 (mean + standard deviation: 4.0 + 2.3) animals observed
per person-hour of search time. This
species was most often found among vegetation, but was also found in detritus,
root wads, and woody debris. This
species occurred in various types of sites, representative of most sites
sampled, with flow ranging from stagnant to a moderate gradient. Species associates included Cambarus sp.C
and Procambarus braswelli.
At 23 sites, no species other than P. blandingii were observed;
and at 4 sites, no species other than P. acutus/blandingi were present. Of 126
individual P. blandingii observed, 124 were measured (carapace length),
and sizes ranged from 4.5 to 45.9 mm, with a mean + standard deviation
of 20.6 + 10.3 mm. Of 8
individual P. acutus/blandingii observed, all were measured (carapace
length), and sizes ranged from 14.0 to 38.0 mm, with a mean + standard
deviation of 20.2 + 7.8 mm.
Reproduction was evident, indicated by the presence of 4 form I males and
juveniles at over half of the sites where this species occurred.
Procambarus blandingii was observed at 9 of the 32
sites surveyed in the Waccamaw River Basin
(see associated map for sites surveyed), and abundance ranged from 2.7 to 30.0
(mean + standard deviation: 6.8 + 8.8) animals observed per
person-hour of search time. Procambarus acutus/blandingii was observed at 8 of
the 32 sites surveyed in the Waccamaw River Basin, and abundance ranged from
1.3 to 26.9 (mean + standard deviation: 11.8 + 10.2) animals
observed per person-hour of search time. This species was most often found
among vegetation, but was also found in detritus, root wads, and woody
debris. This species occurred in
various types of sites, representative of most sites sampled, with flow ranging
from stagnant to a moderate gradient.
Species associates included Procambarus ancylus and Procambarus
braswelli. At 8 sites, no species
other than P. blandingii were observed; and at 2 sites, no species other
than P. acutus/blandingi were observed. Of 33 individual P. blandingii observed,
32 were measured (carapace length), and sizes ranged from 8.5 to 47.3 mm, with
a mean + standard deviation of 25.7 + 13.1 mm. Of 50 individual P. acutus/blandingii observed,
47 were measured (carapace length), and sizes ranged from 5.2 to 30.5 mm, with
a mean + standard deviation of 13.5 + 5.0 mm. Reproduction was evident, indicated by the
presence of 7 form I males and juveniles at about half of the sites where this
species occurred.
See the discussion above for
P. braswelli (penultimate paragraph) for potential threats to aquatic
species in the Lumber (and Waccamaw) River Basin.
Of the 46 sites surveyed in
the Lumber River Basin and the 32 sites
surveyed in the Waccamaw River Basin
during this study (see associated maps for sites surveyed), this species was
not observed. However, this species was
observed during previous recent surveys conducted by Nongame & Endangered
Wildlife Program personnel and colleagues, and the potential range map (this web atlas) reflects these
data.
See the discussion above for
P. braswelli (penultimate paragraph) for potential threats to aquatic
species in the Lumber (and Waccamaw) River Basin.
We have yet to thoroughly
survey for this species in the Cape Fear (including
Northeast Cape Fear) River Basin.