Effects of Stargrass Hay Supplementation on ...

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Effects of Stargrass Hay Supplementation on Growth and Survival of Juvenile Redclaw Crayfish Cherax quadricarinatus a

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Antonio Garza de Yta , D. Allen Davis , David B. Rouse , I. Patrick Saoud & Joly Ghanawi

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Department of Fisheries and Allied Aquaculture, Auburn University, 203 Swingle Hall, Auburn, Alabama, 36849, USA b

Department of Biology, American University of Beirut, Bliss Street, Beirut, Lebanon

Available online: 21 Nov 2011

To cite this article: Antonio Garza de Yta, D. Allen Davis, David B. Rouse, I. Patrick Saoud & Joly Ghanawi (2011): Effects of Stargrass Hay Supplementation on Growth and Survival of Juvenile Redclaw Crayfish Cherax quadricarinatus , North American Journal of Aquaculture, 73:4, 484-488 To link to this article: http://dx.doi.org/10.1080/15222055.2011.635244

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North American Journal of Aquaculture 73:484–488, 2011 C American Fisheries Society 2011 ISSN: 1522-2055 print / 1548-8454 online DOI: 10.1080/15222055.2011.635244

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Downloaded by [American University of Beirut], [I. Patrick Saoud] at 22:59 21 November 2011

Effects of Stargrass Hay Supplementation on Growth and Survival of Juvenile Redclaw Crayfish Cherax quadricarinatus Antonio Garza de Yta,* D. Allen Davis, and David B. Rouse Department of Fisheries and Allied Aquaculture, Auburn University, 203 Swingle Hall, Auburn, Alabama 36849, USA

I. Patrick Saoud and Joly Ghanawi Department of Biology, American University of Beirut, Bliss Street, Beirut, Lebanon

Abstract Hay is used as supplementary forage for crayfish aquaculture in many farms around the world. However, our understanding of the relative contribution of hay to crayfish dietary requirements is limited. In the present work, 36 juvenile redclaw crayfish Cherax quadricarinatus were stocked into each of 28 tanks that received water continuously from a pond. Four replicate tanks were assigned to each of seven dietary treatments: commercial formulated feed (FF) only, at a ration calculated to produce optimal growth; 100% of the calculated FF ration plus the hay of stargrass Cynodon nlemfuensis added at 150 kg·ha−1·week−1; 75% of the FF ration plus hay; 50% of the FF ration plus hay; 25% of the FF ration plus hay; hay only; and no feed (control). At the end of 8 weeks, the crayfish were harvested, counted, and weighed. There were no significant differences in survival among treatments (α = 0.05), and crayfish growth did not differ among tanks that were offered FF. Redclaw crayfish in the hay-only treatment grew less than those that were offered FF, but growth did not differ between crayfish that were offered only hay and crayfish in the no-feed control. Although hay did not contribute to the growth of redclaw crayfish that were offered the high-protein shrimp feed, it did allow for survival and minimal growth of crayfish that were not offered FF. Accordingly, hay might contribute to growth if a low-protein, low-energy diet is developed specifically for crayfish.

In many parts of the world, crayfish aquaculture depends on natural forage as a major food source. Planted forages— mainly rice and to a lesser extent hay—have been used in the southern United States to support a detritus-based system that has proven to be reliable and cost effective for the nourishment and production of the red swamp crayfish Procambarus clarkii (Avault and Brunson 1990; McClain et al. 1998). In Australia, *Corresponding author: [email protected] Received February 25, 2011; accepted April 26, 2011

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the use of forage (with or without the use of artificial diets) has been a common practice for extensive and semi-intensive farming of crayfishes Cherax spp. (O’Sullivan 1992; Geddes and Smallridge 1993). In Latin America, commercial farms that produce redclaw crayfish Cherax quadricarinatus supplement formulated feeds (FFs) with the hay of stargrass Cynodon nlemfuensis applied at a rate of approximately 1,235 kg/ha (1,100 lb/acre) per month, as was recommended by Masser and Rouse (1997). Crayfishes are omnivorous scavengers, and stomach content analyses of various astacid and cambarid species indicate that selective feeding occurs during ontogeny but that the crayfish become much less selective as adults. The relative proportions of plant and animal material consumed are age (or size) related; for example, juveniles may have a greater animal-based food requirement than adults (Goddard 1988; Jones 1990). LoyaJavellana et al. (1993) found that decayed plant material is the preferred food of young and subadult redclaw crayfish if they are given the opportunity to choose between decayed plants and zooplankton. However, zooplankton and decayed plant material were equally acceptable to early independent young if both foods were offered simultaneously. The use of aquatic plants in combination with FF for raising juvenile crayfish is well documented (Celada et al. 1989; Jones 1995). Celada et al. (1989) found that the addition of fresh aquatic plant material to pelleted diets improved growth and slightly increased survival of juvenile signal crayfish Pacifastacus leniusculus. Pinto and Rouse (1996) obtained good growth and survival and a feed conversion ratio (FCR) of 1.39 when using FF (25% protein) with a combination of hay and corn silage

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at a rate of 500 kg·ha−1·month−1 in redclaw crayfish grow-out ponds in Alabama. Metts et al. (2007) reported similar results for redclaw crayfish that were given FF (13% protein) along with dry hay of alfalfa Medicago sativa administered at a rate of 500 kg·ha−1·month−1. Researchers have tested various dietary ingredients and ingredient mixes to develop feeds for juveniles of various crayfish species (Huner et al. 1975; Morrissy 1984; Celada et al. 1989; McClain et al. 1992a, 1992b; Jones et al. 1995; Gonz´alez et al. 2008). For juvenile redclaw crayfish, Jones (1995) evaluated fresh zooplankton and a high-protein formulated flake diet in the presence and absence of the floating aquatic macrophyte Pistia stratoites. Additionally, several trials have been conducted to evaluate the rearing of juvenile redclaw crayfish with artificial diets only (Manomaitis 2001; Muzinic et al. 2004; Thompson et al. 2005; Saoud et al. 2008). Many farmers and researchers report anecdotal evidence of better redclaw crayfish performance when forage material is supplemented to ponds, but pond experiments are difficult to control and benefits might have resulted from some factor other than the forage being tested. We investigated the contribution of hay to redclaw crayfish growth by performing the experiments in indoor tanks. The effects of feeding dry stargrass hay on the growth and survival of juvenile redclaw crayfish offered various amounts of FF were evaluated. METHODS Juvenile redclaw crayfish released from the mother during a 48-h period were collected and placed in an indoor nursery tank at the AGY Redclaw Hatchery (property of Megar Sociedad Anonima de Capital Variable in Soto La Marina, Tamaulipas, Mexico). At 24 d of age, juveniles were harvested and manually sorted to remove large and small individuals. Fifty of the remaining individuals were selected randomly, individually weighed, and then returned to the group. The juveniles (individual weight [mean ± SD] = 0.125 ± 0.025 g) were then separated into

groups of 36 crayfish, which were stocked into each of 28 rectangular tanks (2.4 × 1.2 × 0.1 m; 288-L volume; 2.88-m2 bottom area). Each tank received water from an outdoor earthen pond with a water flow of approximately 20 L/h. Tanks contained 36 pieces of 5-cm-diameter polyvinyl chloride pipe (used for refuge) and four submerged air diffusers (for aeration and water mixing). Individual tanks were randomly assigned to one of seven experimental treatments (4 replicates/treatment). Based on previous work, mean weights of the crayfish were assumed to double during each of the first 3 weeks (0.125, 0.25, and 0.5 g of weight gain for weeks 1, 2, and 3, respectively), and the crayfish were assumed to grow at 1.0 g/week thereafter when offered a diet similar to that used in the present experiment. Accordingly, based on the expected growth rates and an FCR of 1.5, a FF ration was calculated and considered to be the requirement for optimal growth (i.e., the 100% FF ration). The feed used in the present experiment was specially manufactured by Rangen (Angleton, Texas) in accordance with a recipe we developed; the FF contained 35% crude protein, 7% lipid, and 3% fiber. Seven treatments, designated A–G, were applied as follows. Treatment A received only the 100% FF ration. Treatment B received the 100% FF ration and stargrass hay administered at 150 kg·ha−1·week−1. Treatments C, D, and E received the same amount of hay but only 75, 50, and 25% of the FF ration, respectively. Treatment F received only hay, and treatment G did not receive any feed for the duration of the 8-week growth trial (see Table 1). The treatments that received FF were fed once daily in the evening (∼1600 hours). Hay was offered weekly on Mondays, but hay remaining from the previous week was not removed. Proximate composition of hay in the present work was not assessed, but Maya et al. (2005) reported it to be 10.85% protein and 1.45% lipid. Dissolved oxygen concentration, temperature, and pH were measured twice daily with a YSI Model 55 dissolved oxygen meter (Yellow Springs Instrument, Yellow Springs, Ohio)

TABLE 1. Feeding regimens for redclaw crayfish juveniles that were stocked in tanks at an initial weight of 0.125 ± 0.025 g (mean ± SD) and maintained for 8 weeks (FF = formulated feed; NA = not applicable). Calculations assume a weekly doubling in size during the first 3 weeks and a growth rate of 1 g/week thereafter.

Treatment Experimental variable FF (% of calculated optimal ration)a Stargrass hay added? Number of juveniles per tank Total forecast growth over 8 weeks (g) Assumed feed conversion ratio Total FF per individual (g) Total FF per tank (g) Weekly hay administered per tank (g) Total hay administered per tank (g) a

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100 No 36 5.9 1.5 8.8 317.3 0 0

100 Yes 36 5.9 1.5 8.8 317.3 4.32 345.6

75 Yes 36 5.9 1.125 6.6 237.9 4.32 345.6

50 Yes 36 5.9 0.75 4.4 158.6 4.32 345.6

25 Yes 36 5.9 0.375 2.2 79.3 4.32 345.6

0 Yes 36 5.9 NA 0 0 4.32 345.6

0 No 36 5.9 NA 0 0 0 0

The FF (manufactured by Rangen, Angleton, Texas) contained 35% crude protein, 7% lipid, and 3% fiber.


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and a hand-held pH meter. Ammonia nitrogen was measured biweekly with a LaMotte Freshwater Aquaculture kit (LaMotte Co., Chestertown, Maryland), and alkalinity was measured in the pond water at the beginning of the experiment. At the conclusion of the 8-week growth trial, crayfish were counted and individually weighed. Weight gain, percent survival, and FCR were calculated. Data from the feeding trial were analyzed with one-way analysis of variance and Tukey’s honestly significant difference test to determine significant differences (P ≤ 0.05) among treatment means. All statistical analyses were performed with MINITAB version 15.1 (MINITAB, Inc., State College, Pennsylvania). RESULTS AND DISCUSSION Redclaw crayfish farmers around the world typically rear their animals on formulated shrimp feeds because speciesspecific feeds are typically not available. Although these feeds supply essential nutrients, it is believed that the omnivorous scavenging redclaw crayfish can obtain a considerable portion of its nutritive needs from the primary production of the pond as well as from forage materials that are supplemented to the pond. Many farmers add hay to their redclaw crayfish ponds to take advantage of this perceived phenomenon. In the present experiment, redclaw crayfish maintained on the treatment without supplemental feed or hay (treatment G) survived well (75%; Table 2) and had access to sufficient primary production to support minimal growth. It is quite possible that Cherax spp. can graze on bacterial flocs and protozoal growth in the tanks. This would be an important feature in organisms that have evolved to live in oligotrophic waters. Water quality remained within optimal ranges for redclaw crayfish. Temperature averaged 27.8 ± 0.8◦ C (mean ± SD), TABLE 2. Survival, final weight, and feed conversion ratio (FCR; calculated as total formulated feed [FF] offered/biomass increase) of juvenile redclaw crayfish that were stocked in tanks at an initial weight of 0.125 ± 0.025 g (mean ± SD) and were offered various rations of FF and dry stargrass hay during an 8-week culture period (PSE = pooled SE of treatment means; n = 4). Percentages of FF for each treatment refer to the percentage of the calculated optimal ration (e.g., 100% FF indicates that the full ration was applied). Within a given column, means with different letters are significantly different (StudentNeuman-Keuls’ test: P < 0.05).

Treatment

Survival (%)

Final weight (g)

A (100% FF) B (100% FF + hay) C (75% FF + hay) D (50% FF + hay) E (25% FF + hay) F (hay only) G (no feed) PSE P-value

90.3 90.3 88.9 70.1 86.1 77.1 75.0 5.980 0.124

4.04 z 5.11 z 4.26 z 4.73 z 5.08 z 0.91 y 0.54 y 0.373