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Browsing by Subject "Crayfish"

Now showing 1 - 3 of 3
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    Attraction and Consumption of Crayfish by Centrachids
    (University of Minnesota Duluth, 1996-07) Breneman, Dan; Richards, Carl; Gunderson, Jeffrey; McDonald, Michael E
    Fish attractants are a small but stable component of the U.S. recreational fishing industry, generating $28.1 billion in 1985. Subsequently, fish attractant manufacturers compete for a share of the market, introducing new products annually. Although dilute concentrations of scent have been shown to influence fish behavior, there is little published information regarding the effectiveness of today's marketable products. As a demand for commercial attractants utilizing crayfish scent increases, the need to document crayfish attracting capabilities through fish behavioral research becomes more pertinent. To date, there are few fish attractant products on the market that utilize softshell crayfish, creating an identifiable marketing niche for:crayfish products. Commercial products utilizing Minnesota's abundant crayfish population would further develop Minnesota's crayfish industry, and assist local businesses in competing in the fish attractant market. The mechanism of odor detection in fish is well known. It is also well established that many fish species can detect odors with concentrations in the parts per billion or even parts per trillion. Taste and odor detection in fish is difficult to separate because both senses detect molecules dissolved in water. Odor has been described as distant chemoreception, while taste is nearby or contact chemoreception. Taste detection of molecules dissolved in water can be as sensitive or even be more sensitive than the sense of smell. The spectrum and minimum concentration detected by both olfaction and taste varies greatly between species. A variety of fish behaviors are influenced by odor. These behaviors include: 1) homing migrations, 2) feeding, 3) reproduction, 4) fright reactions, and 5) schooling. Feeding behavior is influenced by both olfaction and taste. The odors most frequently identified as eliciting fish behavior responses have been amino acids and bile acids. Several individual amino acids and combinations of amino acids have been found to elicit olfactory-mediated feeding responses in fish. Other compounds and some amino acid-like components have also been shown to elicit feeding responses. It is generally believed that scent which elicits the greatest response will most often contain mixtures of compounds rather than single substances. Studies attempting to correlate feeding behavior response to olfactory stimuli are limited and have not been conducted on primary U.S. recreational fish species. Two methods have been used to evaluate olfactory responses in fish: 1) behavioral studies, and 2) electrophysiological response of anesthetized fish. Electrophysiological studies are similarly limited in scope and are not necessarily suitable predictors of feeding behavior since they only detect physiological stimulation and not instinctive foraging activity. Soft crayfish are more desirable than hard shell crayfish for use as angling bait, presumably because a perception exists that soft crayfish are a more effective in catching fish. Glycine betaine (found in marine invertebrates and elasmobranch fish, but not in teleost fish) increases the attractiveness of amino acids combinations. Based on reports describing the effectiveness of live and dead crayfish as bait to attract marine crustaceans, it is possible that crayfish possess the amino acid combinations that would attract popular recreational species. While many species universally respond positively to certain amino acids, even closely related species can vary significantly in their response. Crayfish are readily consumed by a variety of fish species including smallmouth bass, largemouth bass, walleye, yellow perch, catfish and others. Major physiological changes occur as crayfish grow. The transformation results in individuals shedding a hard exoskeleton. Following the molt, crayfish are soft, have limited coordination, and are completely vulnerable to predators or other crayfish. As a result, they secure secluded locations to molt and allow the new shell to harden. Since crayfish are vulnerable during the time immediately post molt, it is likely that they would be especially attractive to fish. An odor that is unique to this highly vulnerable life stage may be more attractive than odors from a hard shell crayfish.
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    Crayfish and Baitfish Culture in Wild Rice Paddies
    (University of Minnesota Duluth, 1995-09) Richards, Carl; Gunderson, Jeffrey; Tucker, Paul; McDonald, Michael E
    The objectives of the report are to identify the influence of time of capture, crayfish size, sex, and eyestalk ablation on soft shell crayfish production; to examine crayfish harvest in production-sized wild rice paddies under simulated commercial harvesting; to examine the influence of crayfish densities on wild rice depredation; to asses sucker production potential in wild rice paddies; to assess the potential of aeration for influencing the growth and survival of baitfish and crayfish in wild rice paddies; to assess the commercial viability of softshell crayfish production; to transfer results of this research to potential entrepreneurs, fish farmers, and other interested persons,
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    Economic and Technologic Development for the Crayfish Industry in Minnesota: Final Report
    (University of Minnesota Duluth, 1992) McDonald, Michael E; DeVore, Philip; Richards, Carl; Skurla, James A; Gunderson, Jeffrey; Kutka, Frank; Merrick, Glenn
    The potential to develop a viable crayfish industry in Minnesota currently exists. Crayfish biomass in our inland lakes can greatly exceed that of fishes; existing harvest techniques appear to have very little impact on the year-to-year crayfish population. Thus, Minnesota's crayfish appear to be an abundant and resilient resource. There are markets for soft and hard shell crayfish for food, soft and hard shell crayfish for bait, and peeled tail meat. A Minnesota crayfish product could currently be inserted in any of these markets, but crayfish as a bait appears to be the most attractive market. There is a very high seasonal demand for bait crayfish and the wholesale prices can be in the range of $15 to $25 per lb for soft shells. In addition to bait markets, large hard shell crayfish for food have a strong international export market, but this market requires that sufficient quantities be shipped at the right times. Also, there is local interest in peeled tail meat for retail sale. We examined four widely distributed Orconectes species (O. virilis, O. propinquus, O. rusticus, O. immunis) to assess commercial soft shell production potential. Crayfish were held in production-sized shallow trays with 2 cm of water at constant temperature similar to that used for commercial soft shell production. Molting success was examined as a function of capture date, sex, and stage of maturity. The timing of life cycle events dictates to a large extent the availability and soft shell production potential of wild caught crayfish, particularly in northern latitudes where market-sized crayfish are often nonjuveniles. Adults typically molt two to three times per growing season, associated with reproductive cycles. Molting rate in the laboratory was highest when crayfish were captured just prior to the wild molt. The first molt of the season was much more synchronous than the second molt. Molt timing varied by sex. Premolt Orconectid crayfish did not change color like Procambarus sp. but could be identified by the decalcification of the cheliped merus. The harvest of several species may be required to optimize soft shell production since synchronous molts occur at different times for different species. Our economic assessment of the crayfish food market suggests that it is relatively flat. This is due to: continued high production costs (including the lack of a proven tail meat separator); regional consumption (primarily in the south-central and Pacific states); unsophisticated packaging and marketing; and seasonally available supply. Crayfish are used in much of the Midwest for fishing bait. Since it is illegal to sell live crayfish for bait in Minnesota, markets in other states will have to be targeted. Problems to overcome include reducing mortality of crayfish shipped to out-of-state markets and drops in sales when crayfish are available closer to the markets. We have analyzed the economic feasibility of food and bait soft shell crayfish production facilities using flow-through and recirculating systems for the first two years of operation. Bait crayfish production in a recirculating system appeared to be the most profitable operation and food crayfish production in a flow-through system appeared to be the least profitable operation. The processing of large quantities of crayfish for a commercial tail meat operation in Minnesota requires that an inexpensive, automated system be developed in order to maintain the product's economic viability. We have evaluated the necessary engineering design components for developing a relatively inexpensive automated crayfish processing system, which could be linked to extant tail meat extruders. We feel that such a system is feasible, and could cost less than $15,000 retail.