Table of Contents
Brown, P.B. 1993. Soft-shell crayfish: A new crop for
the Midwest. p. 654-656. In: J. Janick and J.E. Simon (eds.), New crops.
Wiley, New York.
Soft-Shell Crayfish: A New Crop for the Midwest*
Paul B. Brown
- Economics and Marketing
- RESULTS AND DISCUSSION
- Table 1
- Fig. 1
Crayfish production consistently ranks as one of the largest aquacultural
industries in the United States, typically the second largest industry behind
culture of channel catfish (USDA 1991). The primary production areas include
Louisiana, Texas, Arkansas, and other southern states, and annual production
ranges from 35 to 55 million kg (Huner and Barr 1984; Roberts and Harper 1988).
However, supplies of fresh crayfish from those areas are seasonal, typically
available from December through June (Huner 1990; Huner and Romaire 1990).
Reproductive characteristics of native midwestern crayfish species are offset
seasonally from crayfish in the South (Page 1985; Hobbs and Jass 1988); thus,
production may be seasonally offset. Preliminary studies to date indicated
that the production season in the Midwest will be June through November (Brown
et al. 1990). Thus, midwestern farmers have an opportunity to fill a market
niche with a native species at a time of year when there is no competition for
Crayfish production can be divided into two distinct segments: hard- and
soft-shell production (Huner 1990; Huner and Romaire 1990). Hard-shell
producers market tail meat, similar to shrimp production, while soft-shell
producers market the entire body, similar to soft-shell crab production.
Soft-shell production requires a dependable source of relatively large,
Studies conducted in our laboratory have indicated significant potential for
pond production of native species for the tail-meat market (Table 1). In our
first attempt at producing the northern or fantail crayfish (Orconectes
viriles), production levels were dependent on initial stocking strategy,
but ranged from 323 to 807 kg/ha when fed agricultural forages (Brown et al.
1990), which compares favorably with average production levels in the South of
545 to 691 kg/ha (Roberts and Harper 1988). That initial study and two
regional symposia on crayfish culture stimulated a great deal of interest in
crayfish and construction of ponds was initiated. The next step in providing
opportunities to midwestern farmers is evaluation of soft-shell production.
A typical scenario in producing soft-shell crayfish involves collecting or
harvesting hard-shell crayfish from wild populations or aquaculture ponds and
transporting them to an indoor, controlled molting facility. Groups of
crayfish are then stocked into relatively shallow tanks (<0.3 m), fed any of
a variety of feeds including potatoes, whole fish, carrots, or one of the new
formulated diets for crustaceans, and premolt individuals are identified and
moved to separate molting tanks (Culley et al. 1985). All crustaceans are
cannibalistic, particularly when one of their cohorts molts in a communal tank;
thus, identifying and moving premolt animals is an important economic
Soft-shell producers in the South purchase crayfish for $0.07 to 0.50 per kg,
transport those animals to controlled, indoor tanks, and wait for the animal to
molt, which typically takes 1 to 4 weeks. Soft-shell crayfish retail for $1.80
to $3.60 per kg. Thus, the profit margin and relatively quick turnover of
product entices many farmers into soft-shell production.
Markets for crayfish have been expanding in recent years. The market in
northern Europe is especially promising, as several festivals in the fall of
each year are centered on consumption of crayfish, yet their native species
have been decimated by an introduced fungal epidemic (Huner 1990). Southern
producers can supply only frozen product during that portion of the year,
whereas midwestern producers can supply fresh product.
Our objective in this research was to evaluate the potential of soft-shell
production of crayfish using one of the more promising midwestern species,
O. viriles. Specifically, we examined the effects of selected rearing
temperatures on molting frequency.
Northern crayfish were obtained in September from a producer in Indiana and
transported to the Purdue University Aquacultural Research Laboratory. Those
individuals weighed 20 to 55 g and pond water temperature was 19° to 24°C
at the time of collection. Crayfish were divided into similar groups (equal
numbers of male and female) and immediately stocked into crayfish molting trays
(2.0 x 0.8 x 0.1 m). Water temperatures were set at either 20°, 25°, or
30°C using submersible chillers or heaters and triplicate tanks were used at
All crayfish were fed a commercially-available crustacean diet (Zeigler
Brothers, Gardners, PA) to satiation twice daily and individual premolt
crayfish (those individuals within 1 to 2 days of molting) were removed to
separate tanks. Cumulative molt and survival data were collected from each
Both male and female crayfish molted at the three temperatures; there were no
significant differences among sex. Those reared at 20°C exhibited the
largest number of successful molts and the fewest numbers of deaths (Fig. 1),
while number of successful molts declined and numbers of deaths increased with
increased temperatures. Differences observed at 20deg. vs. 30°C were
significantly different (P<0.05). Unpublished data from our laboratory
indicated that 25°C was optimal for juvenile O. viriles and weight
gain of crayfish at 25°C was significantly higher than those reared at
20°C. Thus, optimal temperature for growth may decrease in older animals.
While the absolute numbers of crayfish that molted over the 30-day experimental
period was higher at 20°C compared to higher temperatures, a higher
percentage molted in a shorter period of time at 30°C than at lower
temperatures. That molting activity was completed prior to significant
increases in mortality. Thus, more rapid turnover of crayfish from molting
facilities may be possible using controlled temperature manipulations.
Regardless of temperature, there was a biphasic response of molting activity.
That response became more dramatic as temperature increased from 20° to
30deg.C. In general, a large number of crayfish molted within the first 5 to
10 days (as many as 64% of the population reared at 30°C), followed by a
quiescent period, then another period of molting. This observation has
important management implications. For example, if an economically-large
segment of any population molts within a shorter period of time than expected
(up to 4 weeks), then more rapid turnover of that commodity may be possible,
thereby increasing the amount of marketable product through a production
season. Several other factors such as length of photoperiod and water levels
may influence molting frequency and synchronization within a given population.
Native midwestern crayfish will molt in controlled situations and that molting
is influenced by water temperature. Molting activity is relatively rapid, with
a large percentage occurring within the first 10 days. The response,
regardless of temperature, was biphasic and probably reflects individuals in
different stages of the molt cycle when acquired. Those that were near stage E
(ecdysis) in the molt cycle molted within the first 5 to 10 days, while those
is earlier stages required approximately 15 days to molt. Management options
are now available to aquaculturists that will allow more carefully manipulated
molting activity patterns in populations of native midwestern crayfish. The
results of this study should be considered promising and, coupled with ongoing
studies in our laboratory, will facilitate growth of the crayfish industry in
- Brown, P.B., M.L. Hooe, and W.G. Blythe. 1990. Preliminary evaluation of
production systems and forages for culture of Orconectes viriles, the
northern or fantail crayfish. J. World Aquaculture Soc. 21:53-58.
- Culley, D.D., M.Z. Said, and E. Rejmankova. 1985. Producing soft crawfish: a
status report. Louisiana Sea Grant Program, Center for Wetland Resources,
- Hobbs, H.H., III and J.P. Jass. 1988. The crayfishes and shrimp of Wisconsin.
Milwaukee Public Museum, Milwaukee.
- Huner, J.V. 1990. Biology, fisheries, and cultivation of freshwater
crawfishes in the US. Rev. Aquatic Sci. 2:229-254.
- Huner, J.V. and J.E. Barr. 1984. Red swamp crawfish: biology and
exploitation. Louisiana Sea Grant Program, Louisiana State Univ., Baton
- Huner, J.V. and R.P. Romaire. 1990. Crawfish culture in the southeastern USA.
World Aquaculture 21:58-65.
- Page, L.M. 1985. The crayfishes and shrimps (Decapoda) of Illinois. Illinois
Natural History Survey Bul. 33:335-448.
- Roberts, K.J. and C.D. Harper. 1988. Seafood market trends. Louisiana Coop.
Ext. Serv., Baton Rouge.
- USDA. 1991. Aquaculture situation and outlook report. USDA, Commodity
Economics Division, Economic Research Service. Washington, DC.
*This study was funded by the Indiana Corporation for Science and Technology
(now the Business Modernization and Technology Corporation).
Table 1. Mean production of northern crayfish (Orconectes
viriles) in deep or shallow pondsz.
zData from Brown et al. (1990).
|Wheat straw ||457±107|
|Corn silage ||323±163|
|Negative control (no inputs) ||422±216|
|Wheat straw ||807±41|
|Corn silage ||784±101|
|Negative control (no inputs) ||779±73|
yMeans of three replications.
||Fig. 1. Mean cumulative number of male (M) or female (F) crayfish that
molted (molt) or died (mort) when reared at 20° (A), 25° (B), or 30°C
Last update September 19, 1997