Replicate Ponds Research Articles

Effect of pellet-size on fish growth, feeding behaviour and natural food web in pond polyculture

In carp-tilapia pond polyculture, carps are stocked once and usually harvested each 12 to 24 months, while, tilapia is stocked and harvested each 4 to 6 months. Therefore, per carp cycle there are 3 to 6 tilapia cycles. With time, carps grow bigger while tilapia reach only 10 to 50% the mass of carps. Pellet size can offer a feeding management tool in the ponds with large carp and small tilapia. This experiment investigated whether pellet-size can steer the growth of large carps (∼ 500 g) and small tilapias (∼30 g) in polyculture ponds. Four pellet-size treatments were applied in this study, each with a different combination of small (2 mm) and large (6 mm) pellets (on weight basis): S100L0 (100% small, 0% large), S50L50 (50% small, 50% large), S25L75 (25% small, 75% large) and S0L100 (0% small, 100% large). Each treatment was applied to six replicate ponds. The experiment lasted for 8 weeks. The treatments did not alter carp production, but tilapia production was highest in S100L0 treatment ponds (P < 0.001). The fish always needed more time to consume large pellets than the small pellets. Small pellets were consumed much quicker when the portion fed was small, indicating strong competition. A similar trend was observed with large pellets but the difference in feed intake time across the treatments was smaller than with small pellets. This is because tilapia ate the majority of both small and large pellets while carps ate less pellets. Tilapia at treatment S0L100 had a lower protein and fat content and a higher ash content than at the other pellet-size treatments. Carp's body composition remain unaffected by pellet-size treatment except the ash content of rohu which was highest at S100L0 and lowest at S0L100. By volume, tilapia had a higher amount of food in the stomach in treatments S100 L0 and S50L50 than in the other treatments. In contrast, more food was found in the gut of rohu in treatments S0L100 and S25L75 than in the other treatments. Pellet-size treatments did not affect water quality and the pond food web (P > 0.05) except phytoplankton diversity which was positively influenced when feeding more large pellets. The plankton population increased with the progression of the experiment, suggesting the food web was not fully exploited. In conclusion, pellet-size proves to be a feeding management tool to steer the production of tilapia as well as of total fish biomass, but not of carp's biomass in carp-tilapia pond polyculture.

Periphyton: A natural fish food item for replacement of feed at optimized substrate surface area for cost-effective production in brackishwater polyculture

Periphyton community grown on submerged substrate in water could serve as a preferred natural food item to herbivorous and omnivorous fish and crustacean species. To determine the optimum substrate area for the growth of periphyton biomass serving as natural food and to reduce the requirement of pellet feed quantity, a 150-day pond experiment was conducted with four treatments of brackishwater polyculture: total feeding and no periphyton substrate (P0), and partial feeding with periphyton grown on nylon net substrate equivalent to 50 (P50), 75 (P75) and 100 (P100) % of pond surface area. Each treatment had three randomly assigned replicate ponds (50 m2). After 15 days of substrate fixation in the surface layer of ponds up to 50 cm water depth, stocking was made with seeds of Mugil cephalus Linnaeus, 1758, Planiliza parsia (Hamilton, 1822), Chanos chanos (Forsskål, 1775) and Penaeus monodon Fabricius, 1798 at 1800, 18000, 2000 and 30,000 number ha−1, respectively. A low-cost pellet feed (30.76% crude protein) was provided at 6–3% of fish biomass per day. Dry matter (DM) of periphyton biomass was estimated from each replicate pond under P50, P75 and P100 from 15 × 15 cm2 net substrate, and then total periphyton DM was calculated according to the substrate surface area at 15-day intervals. Then, the total periphyton biomass was divided to find out daily DM availability. The feed amount in P50, P75 and P100 ponds was reduced proportionately to the equivalent daily periphyton DM availability and the feeding at this reduced quantity was continued for 15 days. The experiment revealed significantly lower levels of nitrogenous and phosphorus compounds, and dissolved organic carbon content in water of P75 and P100, compared to that of P0 and P50 (P < 0.05) and there were interaction effects of experimental period and periphyton substrate area on these parameters. All the species had an increasing growth pattern with experimental period and there was an interaction effect of experimental period and periphyton substrate area on growth of these species, indicating periphyton had positive effects. The highest specific growth rate was recorded in P. monodon and the lowest was in M. cephalus. Pooled survival of fishes and shrimp, and total productivity did not differ among treatments (P > 0.05). Although, the highest level of feed reduction (42%) by the utilization of periphyton biomass was in P100, P75 performed better in terms of productivity and economic return with 30% feed reduction in polyculture. Similarly, there was 26–41% reduction in feed conversion ratio with the highest level being in P100 (41%), followed by P75 (40%) in comparison to P0. Moreover, carcass composition of cultured fishes and shrimp indicated that periphyton based systems with partial feeding could meet up the nutrient requirement of the animals with no negative effects in comparison to the feed-based system. Therefore, this study suggests that provision of periphyton substrate equivalent to 75% of pond surface area along with partial feeding is the most appropriate approach for achieving higher return with environmental sustainability in brackishwater polyculture.

Performance of Channel Catfish and Hybrid Catfish in Single‐Batch, Intensively Aerated Ponds

AbstractA pond production trial was conducted to evaluate the economics of raising Channel Catfish Ictalurus punctatus in intensively aerated ponds operated under the single‐batch cropping system. Channel Catfish fingerlings averaging 0.09 lb were stocked at 6,000, 8,000, 10,000, and 12,000 fish/acre with six replicate ponds (1 acre) per treatment. A treatment of hybrid catfish (♀ Channel Catfish × ♂ Blue Catfish I. furcatus) fingerlings stocked into five replicate ponds at 12,000 fish/acre was concurrently evaluated to compare the economic performance of hybrids and that of Channel Catfish. All ponds were provided with a fixed‐paddlewheel aerator (10 hp/acre) and were fed once daily to apparent satiation for 206 d. For Channel Catfish, the gross yield ranged from 6,562 to 9,039 lb/acre, showing nominally linear trends of increasing yield with stocking density. However, the same trend was not seen in the relationship between costs and stocking density: the highest breakeven price (US$1.07/lb) was associated with the lowest density treatment (6,000 fish/acre), and the least cost ($0.96/lb) was associated with the intermediate density of 8,000 fish/acre. Average annual net cash flows from all Channel Catfish treatments were insufficient to make the investment in intensive aeration profitable in the long run (10 years). The hybrid catfish treatment (12,000 fish/acre) outperformed all Channel Catfish treatments in terms of yield (17,542 lb/acre), which offset some of the fixed costs associated with intensively aerated ponds and resulted in a lower cost of production ($0.85/lb) and better long‐term returns (17%). This study indicated that Channel Catfish do not perform well—either biologically or economically—at densities greater than 8,000 fish/acre in single‐batch, intensively aerated ponds. The study reflects current industry trends, where integrated farms (farms with their own processing plants) with yield‐maximizing business objectives prefer raising hybrid catfish in single‐batch systems, while nonintegrated farms prefer raising Channel Catfish in multiple‐batch systems.

Bacillus velezensis AP193 exerts probiotic effects in channel catfish (Ictalurus punctatus) and reduces aquaculture pond eutrophication

Ictalurus punctatus (channel catfish) is an economically important farmed fish particularly in the southeastern United States. Aquaculture sustainability is threatened by disease pressure and the eutrophic conditions resulted from intensive fish farming. Previous research identified Bacillus velezensis strains that reduced mortality due to bacterial pathogens when used as a feed amendment. This study was conducted to determine the effects of B. velezensis-amended feed on catfish growth performance, pond water quality, and on the microbiomes in fish intestines and pond water. B. velezensis AP193 was evaluated in a ten-week pond trial, with four replicate ponds per probiotic treatment or control group. Feed amended with B. velezensis AP193 induced a 40.4% or 32.6% increase in growth relative to control feed in fingerling catfish that originated from aquaria or raceways, respectively. No significant differences were observed in the catfish intestinal microbiota or the pond microbiota due to probiotic-amended feed. The water quality was improved in ponds in which fish were fed with the probiotic-amended feed, as significant reductions were found in total phosphorus (19%), total nitrogen (43%) and nitrate (75%). These data suggest that B. velezensis AP193 can promote catfish growth and improve pond water quality when used as a feed amendment.

Nursery I: The effect of stocking density on the performance of glass eels, Anguilla bicolor in the biofloc system

Glass eels of Anguilla bicolor is an expensive and still abundant commodity in Laguna Segara Anakan, Central Java, Indonesia. However, the growth of glass eels to elver is still a problem because of high mortality in nursery I and II. The objective of the study was to evaluate the result of stocking density on the performance of glass eels in the biofloc system during nursery I. Glass eels were stocked at densities of 54.95, 109.89 and 164.84 fish/m3, respectively, with three replicate ponds for each density. Eels were fed a formulated pasta-diet containing 40% crude protein and , 4% crude lipid, 5% crude fiber, 11.5% ash and 12% moisture, respectively. The water quality were maintained at levels of for fish culture througout the experiements: water temperature was 27.1°C (ranged from 26.3 to 28.2°C), pH (7.6, ranged from 6.8 to 7.8) and DO (7.2 mg.L-1, ranged 6.9 to 7.5 mg.L-1). The results showed that the stocking density did not significantly affect the final weight, weight gain, AGR, SGR, FCR and survival, however this had a significant effect on the yield. The biofloc system was suitable for raising glass eels.

Investigating behaviour for conservation goals: Conspecific call playback can be used to alter amphibian distributions within ponds

Conspecific attraction can prevent occupancy of restored or created habitats by limiting dispersal to unoccupied areas. This may cause problems for threatened taxa where habitat restoration and creation programmes are implemented as part of species recovery plans. Studies on birds have found that the introduction of artificial communication cues such as calling can increase occupancy of restored habitat. The endangered green and golden bell frog (Litoria aurea) has a number of behavioural traits which suggest conspecific attraction occurs via a vocal mechanism, including a loud conspicuous call and large chorusing aggregations. To date, attempts to repopulate restored and created habitat through natural immigration and active translocation of tadpoles and juveniles have been met with limited success for this species. We used L. aurea to determine if distribution could be manipulated via conspecific attraction using artificial communication cues. We placed speaker systems in uninhabited areas of five inhabited ponds across two locations and broadcast calls of L. aurea to see if we could manipulate distribution into previously unoccupied pond areas. Surveys undertaken before and after broadcast indicate that we successfully manipulated L. aurea distribution for adults increasing both occupancy and calling around the speaker locations. This occurred in four of five replicate ponds over three months of experimental treatment, but controls remained low in abundance. We suggest that manipulation of distribution via conspecific attraction mechanisms could be a useful conservation tool for endangered amphibian habitat restoration and creation programmes, resulting in increased occupancy and programme success.

Growth and Survival of Largemouth Bass following Supplemental Feeding of Bluegills in Small Impoundments

AbstractWe investigated whether providing supplemental pellet feed to Bluegills Lepomis macrochirus in small impoundments increased their growth and reproductive rates after stocking and whether the supplemental feeding of Bluegills had positive indirect effects on Largemouth Bass Micropterus salmoides during the initial stocking year. In 2010, we stocked adult Bluegills and Largemouth Bass into nine 0.1‐ha ponds; three replicate ponds were each provided with no pelleted food (control), a low ration (1.52 kg·ha−1·d−1), or a high ration (2.68 kg·ha−1·d−1). Supplemental feeding yielded increases in the growth of newly stocked Bluegills, the gonadosomatic index of female Bluegills, and the density of larval Bluegills within 4 months of stocking. In contrast, the sizes of adult and age‐0 Largemouth Bass and the density and biomass of age‐0 Bluegills during fall were not affected by feeding within the time frame of our study. The results demonstrate that supplemental pellet feeding is useful when the management goal is to increase Bluegill size and reproductive output and that these effects develop soon after stocking. We conclude that supplemental feeding is a beneficial enhancement technique for application to Bluegills in recently stocked impoundments.Received May 13, 2012; accepted November 20, 2012

Experimental evaluation of the culture performance of three exotic and a ‘local’ Giant Freshwater Prawn (Macrobrachium rosenbergii, De Man 1879) culture strain in Fiji

Giant freshwater prawn (GFP; Macrobrachium rosenbergii) aquaculture has expanded rapidly since 1990. Most local culture industries, however, have developed in an unsystematic way. Fiji has a small culture industry producing the ‘Anuenue’ strain; however, performance of this strain has never been systematically evaluated. Recently, some Fijian farmers have reported declines in stock productivity. The current project evaluated the relative performance of three exotic strains with different genetic backgrounds from Malaysia, Indonesia and Vietnam, against the ‘local’ strain in Fiji in a 4 × 3 replicated pond trial experiment. A total of 5827 prawns were harvested after 143 days growout. Individual growth rate and relative survival of the Fiji strain were not statistically different from any of the introduced strains, but Vietnam strain was superior to that of the Malaysia strain. Genetic diversity showed significant differences in variability among strains, with the Malaysian strain displaying the lowest genetic diversity. Indonesia strain showed that females were reaching maturation earlier than other strains and were smaller in size. This study suggests that Malaysian and Indonesian strains would constitute a poor choice for Fiji, whereas the Vietnam strain consistently performed well on all criteria measured. High variation among replicate ponds within strains unfortunately confounded among-strain variation.

The role of pond management for biodiversity conservation in an agricultural landscape

ABSTRACT Debate surrounds the best way to deal with pond terrestrialization so as to maximize landscape‐scale biodiversity. One way of addressing this issue is to re‐set succession via management activities, but the merits of this approach relative to non‐intervention and pond creation are little known. Manor Farm in Norfolk, UK, possesses around 40 ponds, and each year three to four ponds are subject to management involving tree (de‐shading) and/or sediment removal. To determine the consequences of management for pond biodiversity, macrophyte and invertebrate communities were surveyed for replicate ponds covering four ‘time since management’ categories: no management, and managed over the periods 1999–2003, 2004–2006 and 2007–2009. Macrophyte diversity was significantly lower in unmanaged ponds compared with ponds managed in 2004–2006 and 2007–2009. In addition, with the exception of Mollusca, invertebrate diversity was significantly lower in the unmanaged ponds compared with all the managed ponds. A tendency was evident for diversity to peak 3–5 years after management and for a subsequent decline in diversity (significant for macrophytes). No distinctive species assemblages were associated with the different pond successional stages, although several species were confined to individual ponds. Although many species were absent from the non‐managed ponds, especially in the macrophytes and Coleoptera, few species were unique to these ponds. The principal driver of species turnover in the ponds was shade, which was negatively correlated with macrophyte cover. Shade was substantially higher in the unmanaged ponds, whose species‐poor assemblages appeared to be a consequence of low oxygen levels. By arresting succession and restoring macrophyte‐dominated early‐ and mid‐successional ponds, management may have an essential role in biodiversity conservation. In pond‐rich landscapes, where a high proportion of ponds are heavily terrestrialized, management provides a sustainable means both of preserving heterogeneity in the pond network and preventing the loss of large numbers of species which favour early‐ and mid‐successional ponds. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Simulated Storm-Water Runoff Treatment by Duckweed and Algae Ponds

Constructed storm-water wetlands with different types of vegetation are capable of removing organics and nutrients from water while providing other important environmental and ecological services. The objectives of this study were to compare the efficiencies of organic and nutrient removal from a simulated storm-water runoff between the duckweed ponds (DWPs) and the algae ponds (APs) and to establish a potential link between the population of ammonia-oxidizing organisms and effluent water quality. Two replicate ponds were operated under identical conditions in which duckweeds initially thrived off the water, but they were taken over by filamentous algae after the complete removal of duckweeds. The ponds were able to remove 74±4% chemical oxygen demand (COD); 90±3%NH4+-N; 94±2%NO3−-N; and 47±7% orthophosphate in the DWPs in contrast to only 64±6% COD; 77±6%NH4+-N; 85±4%NO3−-N; and 21±6% orthophosphate in the APs. The dissolved oxygen (DO) levels were significantly different between the ponds. In the DWPs, the diurnal DO pattern (from 0.9 to 3.9 mg/L) associated with anoxic-aerobic sequencing conditions was related to the higher phosphorus (P) removal than in the APs. Archaeal and bacterial amoA abundance in the DWPs ranged from (1.1±0.2)×106 to (2.1±0.2)×109 copies/g dry soil and from (1.6±0.3)×107 to (1.1±0.4)×1010 copies/g dry soil, respectively. The hydric soil in the DWPs harbored more ammonia-oxidizing bacteria (AOB) and oligotrophic ammonia-oxidizing archaea (AOA) than any other samples in the ponds by approximately three orders of magnitude. For comparison, the high DO concentrations (an average of 5.5 mg/L) in the APs were linked to the absence of AOA, whereas the abundance of amoA from AOB ranged from (1.3±0.3)×107 to (1.6±0.2)×109 copies/g dry soil. These results suggest that the duckweeds play an important role by creating different microbial niches and cyclic anoxic-aerobic conditions and thus lead to improved organic and nutrient removal.

Evaluation of Reduced Fish Meal Diets for Second Year Growout of the Largemouth Bass, Micropterus salmoides

Abstract Development of efficient cost‐effective diets is a critical component in the refinement of production technologies for the largemouth bass, Micropterus salmoides (LMB). One of the first steps in reducing feed costs can be to decrease the amount of fish meal in the diet. The objective of this study was to evaluate reduced levels of fish meal, and a least‐cost formulation diet, for second year growout of LMB under practical pond conditions. Twelve 0.04‐ha ponds were stocked with juvenile LMB (210.1±3.3 g) at a stocking density of 8650 fish/ha (350 fish/pond). Each pond was randomly assigned one of the four dietary treatments with three replicate ponds per treatment. The three experimental diets contained varying levels of fish meal. Diets FM‐45, FM‐24, and FM‐8 contained 45, 23.5, and 8% fish meal, respectively. In diets FM‐24 and FM‐8, fish meal was replaced by varying levels of poultry by‐product meal, soybean meal, and blood meal. The fourth diet was a commercial salmonid diet widely used as a LMB growout feed (Nelson and Sons, Inc., SilvercupTM, Steelhead, Murray, UT, USA). This diet served as a commercial control (CC) and contained 46% crude protein. The experimental diets were formulated to be isonitrogenous and isocaloric with the CC diet and were fed once daily to apparent satiation for 180 d. At harvest, there were no significant differences between treatments (P &gt; 0.05) in terms of survival, which averaged 95% overall. Mean weights of fish fed the three experimental diets FM‐45, FM‐24 and FM‐8 were not significantly different (P &gt; 0.05) and averaged 518, 546, and 529 g, respectively, but were all significantly greater (P≤ 0.05) than those fed the CC (488 g). Feed conversion ratio (FCR) of fish fed the FM‐45 and FM‐8 diets (1.43 and 1.46, respectively) was significantly greater (P≤ 0.05) than those fed the FM‐24 diet (1.34). The FCR of fish fed the CC diet (1.39) was not significantly different (P &gt; 0.05) from fish fed other diets. Feed cost per unit of weight gain ($US/kg) was significantly lower (P≤ 0.05) in fish fed the FM‐24 and FM‐8 diets ($0.73 and $0.72/kg, respectively) than in fish fed other diets. Feed cost per unit gain of fish fed the FM‐45 diet ($0.83/kg) was significantly lower (P≤ 0.05) than those fed the CC diet ($1.04/kg). There were no significant differences (P &gt; 0.05) in dress‐out percentages or proximate composition among fish fed the four diets. This study indicates that fish meal levels in feeds used for the second year growout of LMB can be reduced to≥8% of the formulation without reducing survival or growth and without negatively impacting body composition.

Evaluation of relative growth performance and genotype by environment effects for cross-bred yellow perch families reared in communal ponds using DNA parentage analyses

From 24 mating sets, 6300 ¢ngerling of yellow perch (Perca £avescens) were stocked into one pond and equal numbers of progeny from six representative sets out of the 24 were stocked into each of two other ponds. After communal rearing for 21 months, total length and body weight were assessed for n 5 300 ¢sh in each of the three ponds and molecular pedigrees were performed for each sampled individual to assign the progeny back to the original parents. The overall average number of alleles per locus was A 516.4 and observed and expected heterozygosities were Ho 5 0.88 and He 5 0.77 respectively. The mean weight of random samples and the top 10% fastgrowing ¢sh from the pond with all the sets was signi¢cantly greater than those from either of the two replicate ponds with six crosses. For the two replicate ponds, no signi¢cant diierences were found in family rankings and assignment of the top10% fast-growing ¢sh, indicating that families with superior growth performance in one pond also exhibited the same superior growth performance in the replicate pond. However, there were no signi¢cant correlations detected in family mean weights of the top 10% ¢sh between any two of the three ponds.

Lack of assortative mating between incipient species of stickleback from a hybrid zone

Both premating and postmating barriers to gene flow can contribute to reproductive isolation but the relative role of these factors, particularly in the early stages of speciation, is not well understood. Evidence suggests that factors contributing to assortative mating and, thus, the development and maintenance of divergent species, can be ecology-dependent. Here, we present results from a study of assortative mating between recently diverged anadromous and freshwater sticklebacks conducted in semi-natural conditions. Sympatric anadromous and freshwater sticklebacks were sampled from a contact zone and multiple male and female morphs were allowed to breed in replicate ponds. Mate choice was determined using genetic markers to assign parents to offspring. Contrary to laboratory-based studies of sticklebacks, after allowing for differences in the propensity of the morphotypes to mate, we found no evidence of assortative mating. Furthermore, there was no evidence of size assortative mating, but rather a general female 'preference' to mate with large males was revealed. Analysis of the propensity of different morphotype combinations to produce fry provided indirect evidence that exogenous factors may influence hybrid survival. Our results indicate that hybridisation between anadromous and freshwater sticklebacks from the River Tyne, Scotland, occurs readily, and that sexual selection is unlikely to contribute to premating isolation. From these results we infer that postmating isolation (hybrid inferiority) has preceded the evolution of premating isolation (assortative mating) in this population of sticklebacks.

A Test of Cues Affecting Habitat Selection by Wading Birds

Abstract We examined foraging-habitat selection by free-ranging wading birds presented with different social and environmental cues by conducting two experiments in eight replicate ponds adjacent to the northern border of the Florida Everglades. The first experiment examined the relative influence of a social (presence of a flock of decoys) and environmental (water depth) cue on the selection of ponds. The second experiment examined the influence of two environmental cues (water depth and fluctuating water level) on the selection of ponds. In the first experiment, wading birds were most attracted to ponds with both the presence of a flock of decoys and shallow water. The social and environmental cues both had the same attractive potential to wading birds. In the second experiment, birds were again attracted to ponds with shallow water; however, fluctuating water level had no significant influence on foraging-habitat selection. If birds do not perceive fluctuating water levels as a cue to habitat quality, then the well-documented relationship between nesting success and fluctuating water levels likely stems from birds responding to factors that covary with water-level changes. Una Prueba de las Señales que Afectan la Selección de Hábitat por Aves Vadeadoras

Use of Alfalfa Hay, Compared to Feeding Practical Diets Containing Two Protein Levels, on Growth, Survival, Body Composition, and Processing Traits of Australian Red Claw Crayfish, Cherax quadricarinatus, Grown in Ponds

Abstract Juvenile red claw, Cherax quadricarinatus, were obtained from a commercial supplier and stocked into twelve 0.04‐ha ponds with an average water depth of approximately 1.1 m at a rate of 1100 red claw per pond (27,170 red claw/ha). Mean stocking weight (±SD) was 6.25 ± 3.0 g. Three replicate ponds were randomly assigned to each of the four treatments. In Treatment 1 (TRT1), red claw were stocked into ponds to which dried alfalfa hay (forage) was added at a rate of 500 kg/ha/mo; Treatment 2 (TRT2) consisted of red claw being fed a prepared diet containing 13% protein; in Treatment 3 (TRT3), red claw were fed a diet containing 13% protein at which had dried alfalfa hay been added at a rate of 500 kg/ha/mo; and in Treatment 4 (TRT4; control), red claw were fed a complete diet containing 28% protein. Water quality measurements were made three times weekly for dissolved oxygen and temperature (am, pm), pH, total ammonia nitrogen, nitrite, and alkalinity averaging 7.17 mg/L, 8.96 mg/L, 25.5 C, 27.3 C, 8.68, 0.39 mg/L, 0.012 mg/L, and 106.5 mg/L, respectively. After 113 d, the final mean weight of red claw fed TRT3 was significantly (P &lt; 0.05) higher (68.10 g) compared to that of red claw fed hay only (49.40 g) but not different from red claw fed TRT2 (56.03 g) and TRT4 (62.10 g). Likewise, red claw fed TRT3 had significantly higher percent weight gain (990%) compared to that of red claw fed hay only (690%) but not different from TRT2 (796%) and TRT4 (893%). Feed conversion ratio of TRT2, TRT3, and TRT4 and percent survival among all treatments did not differ significantly (P &gt; 0.05), averaging 2.85 and 66.8%, respectively. Total yield of red claw fed TRT3 and TRT4 (968 and 952 kg/ha) was significantly (P &lt; 0.05) higher compared to that of red claw fed hay only (617 kg/ha) but did not differ from red claw fed TRT2 (882 kg/ha). Tail meat yield of male red claw in TRT3 was significantly (P &lt; 0.05) higher (17.3 g) compared to that of male red claw in TRT1 (12.7 g) and TRT2 (14.9 g) but not significantly different (P &gt; 0.05) from male red claw in TRT4 (16.9 g). Tail meat yield of female red claw in TRT3 and TRT4 was significantly (P &lt; 0.05) higher (14.2 and 13.9 g, respectively) compared to that of female red claw in TRT1 (10.5 g) and TRT2 (10.4 g). Tail muscle proximate compositions showed no significant differences (P &gt; 0.05) in protein (wet weight basis) between males and females among treatments (diet) which averaged 16.2 and 14.6%; however, there were little to no significant differences in fat and ash between males and females among treatments. Results from this study indicate that pond‐cultured red claw stocked at 27,170 red claw/ha can be fed a practical diet containing 13% protein, with or without forage (alfalfa hay), compared to red claw fed a complete diet containing 28% protein; however, if alfalfa hay is added to the pond at 500 kg/ha/mo as the sole source of added nutrients, growth is reduced. Therefore, the use of alfalfa hay, in combination with a low‐protein pelleted diet may be a production method for pond‐grown red claw that may reduce costs for producers and thereby increase profits.

Effects of diets with different plant proteins on the performance of silver perch (Bidyanus bidyanus Mitchell) and on water quality in earthen ponds

As part of a project to develop least-cost diets with low levels of fish meal, silver perch (Bidyanus bidyanus Mitchell) fingerlings (mean weight, 11.8 g) were stocked at a density of 7500 fish ha−1 into 0.1-ha earthen ponds and fed one of two diets containing 33% digestible protein, 13 MJ kg−1 digestible energy, similar nutrient specifications, but with different levels of fish meal and plant proteins. The reference diet SP35 had 27% fish meal, 28% wheat, 20% soybean and 11% sorghum, while the diet silver perch least-cost (SPLC) had 10% fish meal, 20% peanut meal, 19% wheat, 17% lupins, 16% canola, 8% soybean and 5% blood meal; there were three replicate ponds for each diet. Fish were fed a restricted ration up to 5% body weight day−1 and cultured for 10 months. Survival ranged from 85.9% to 94.3% and was not affected by diet. The mean weight (550 g), specific growth rate (SGR; 1.28% day−1), absolute growth rate (AGR; 1.9 g fish−1 day−1) and production rate (4.5 tonnes ha−1 year−1) were significantly higher (P<0.05) and feed conversion ratio (FCR=1.8) was significantly lower for fish fed SP35 compared with fish fed SPLC (413 g, 1.18% day−1, 1.4 g fish−1 day−1, 3.3 tonnes ha−1 year−1, 2.4). From October (spring) to March (autumn), turbidity was significantly lower (P<0.05) in SPLC ponds than in SP35 ponds, and fish were observed avoiding or ingesting and then expelling SPLC pellets. In February and March, infestations of the ectoparasitic copepod Ergasilus sp. were found on silver perch fed SPLC, and there was 5% post-harvest mortality of these fish. The high inclusion levels of plant proteins, particularly peanut meal and canola in SPLC, may have provided anti-nutritional factors and/or reduced the palatability and intake of the diet, adversely affecting the performance and health of silver perch, and water quality in the ponds. Our study demonstrates the value of evaluating new aquaculture diets under practical conditions over a complete growing period.

A TEST OF CUES AFFECTING HABITAT SELECTION BY WADING BIRDS

Abstract We examined foraging-habitat selection by free-ranging wading birds presented with different social and environmental cues by conducting two experiments in eight replicate ponds adjacent to the northern border of the Florida Everglades. The first experiment examined the relative influence of a social (presence of a flock of decoys) and environmental (water depth) cue on the selection of ponds. The second experiment examined the influence of two environmental cues (water depth and fluctuating water level) on the selection of ponds. In the first experiment, wading birds were most attracted to ponds with both the presence of a flock of decoys and shallow water. The social and environmental cues both had the same attractive potential to wading birds. In the second experiment, birds were again attracted to ponds with shallow water; however, fluctuating water level had no significant influence on foraging-habitat selection. If birds do not perceive fluctuating water levels as a cue to habitat quality, ...

Effect of using different types of organic animal manure on plankton abundance, and on growth and survival of Tilapia rendalli (Boulenger) in ponds

An experiment was conducted to evaluate the effect of using different types of organic manure on the plankton abundance, and growth and survival of Tilapia rendalli juveniles in ponds. Fish weighing 18.15±0.44 g were stocked into 12, 20 m2 ponds at 2 fish m−2 (40 fish pond−1). There were three replicate ponds per treatment (chicken manure, cattle manure, pig manure, and no-manure as a control). After 84 days the T. rendalli in the chicken manure treatment were significantly larger and had higher net annual yields than those in the cattle manure, pig manure and no-manure treatments. The survival rates were not significantly different across the treatments. Significantly higher amounts of chlorophyll a and higher numbers of zooplankton were found in ponds fertilized with the chicken manure treatment. The overall results obtained in this study suggest that the use of chicken manure produces better results than cattle and pig manure treatments on unfertilized ponds.

Over-wintering growth of Macrobrachium rosenbergii (de Man) with carp polyculture in Bangladesh fed formulated diets

An experiment was conducted from December 2003 to April 2004 to observe the over-wintering growth of freshwater prawn, Macrobrachium rosenbergii, with catla, Catla catla and rohu, Labeo rohita in polyculture using formulated diets. The study was conducted in eight experimental ponds, each 80 m2. Three experimental diets containing 30% protein were prepared using fish meal, meat and bone meal, mustard oilcake, rice bran, wheat bran and molasses (binder), and assigned to treatments T1, T2 and T3 respectively. A commercial diet from Saudi-Bangla Fish Feed was assigned to T4 (reference diet). Each treatment had two replicate ponds. Juvenile prawns and catla and rohu fingerlings (initial weight 1.60±0.10, 30.0±1.2 and 25.0±1.1 g respectively) were stocked at a ratio of 2:1:1 (prawn:catla:rohu). A total of 160 prawn and fish (20 000 ha−1) were stocked in each pond. Fish were fed twice daily at 3% body weight (b.w.) for the first 3 months and 5% b.w. for the last 2 months. Prawns in T1 fed diet 1 had significantly higher (P 0.05) among different treatments. Total production ranged between 2196 and 2679 kg ha−1, with T1 showing significantly higher production and net profit (taka 56 531.9 ha−1). The results of the study demonstrated that it is possible to culture M. rosenbergii with carp in polyculture during the winter utilizing the late-produced PLs. Further study is needed to determine the optimum stocking density of M. rosenbergii in carp polyculture.

Efficacy of High-Protein “Finishing” Diets on Growth, Fattiness, and Processing Yield of Channel Catfish, Ictalurus punctatus

Three experiments were conducted to evaluate the use of “finishing” diets in channel catfish, Ictalurus punctatusproduction. Fingerling channel catfish weighing 107, 129, and 103 g for Experiments 1, 2, and 3, respectively, were stocked in 0.04-ha earthen ponds at a rate of 14,820 fish per ha and grown to harvestable size in a single growing season. Four replicate ponds were used for each treatment. In Experiment 1, fish were fed either a 28%- or 32%-protein diet for the entire growing season (controls), or fed the 28%- and 32%-protein diets for part of the growing season and then switched to a 36%-protein “finishing” diet either 30 days or 60 days before harvest. In Experiment 2, fish were fed either a 24%- or 32%-protein diet for the entire growing season (controls), or fed a 24%-protein diet for part of the growing season and then switched to a 32%- or a 35%-protein “finishing” diet for either 30 days or 45 days before harvest. In Experiment 3, fish were fed either a 28%-protein diet for the entire growing season or a 28%-protein diet for part of the growing season, and then switched to a 35%-protein “finishing” diet for either 30, 45, or 60 days before harvest. The data show that a 24%-protein diet is sufficient for maximum growth and feed efficiency of catfish but processing yield is reduced. Further, it appears that feeding fish a 24%-protein diet for most of the growing season and then changing to a 32%- or 35%-protein “finishing” diet for 30 days before harvest, improves carcass yield. Fillet yield also appeared to be improved, but the improvement was slight. The data did not show that “finishing” fish fed a 28%-protein diet on higher protein diets was beneficial in improving processing yield. However, evaluating pooled data from across all of our previous studies, there does appear to be about a 0.4% to 0.5% decrease in processing yield of fish fed a 28%-protein diet. Presently, we do not recommend the use of “finishing” diets, because available data are not consistent, and their benefit is questionable. Also, because of various factors (such as off flavor), one cannot predict with certainty when fish will be harvested.