Does reintroduction stabilize the population of the critically endangered gharial (Gavialis gangeticus,Gavialidae) in Chitwan National Park,Nepal?

• 1 Despite conservation programmes (India 1975, Nepal 1978) gharial populations (Gavialis gangeticus) have declined over their entire distribution range. Information about the current status and main threats is needed to implement effective conservation measures.
• 2 This study presents a survey (2003/2004) of the largest Nepalese gharial population in the Chitwan National Park that has benefited from regular re‐introduction of young gharials since 1981.
• 3 Population size estimates fluctuate between 34 (2003) and 38 (2004). The reintroduction programme, although of limited success, has helped to maintain the gharial population.
• 4 Gharials bask preferentially in large sand banks, and these sites must be protected.
• 5 The main threats are from a dam that causes fish depletion and flushes gharials from the protected area, sand mining and grazing that destroy basking sites, fishing that causes food shortage, drift nets that kill gharial, and water pollution.
• 6 Improvement in the survival of reintroduced gharials is needed. Strict protection of preferred basking sites and prohibition of fishing in the main settling zones are the principal conservation measures while in the long term, education and participatory management by local people are also necessary. Copyright © 2010 John Wiley & Sons, Ltd.

     

The impacts of aquaculture development on food security: lessons from Bangladesh

Fish contribute a significant amount of animal protein to the diets of people in Bangladesh, about 63% of which comes from aquatic animals. In Bangladesh, fish is mainly derived from two sources: capture and culture. Aquaculture has shown tremendous growth in the last two decades, exhibiting by about 10% average annual growth in production. Capture fisheries, although still the major source of supply of fish, have become static or are in decline due to over‐fishing and environmental degradation, and it is now believed that aquaculture has the greatest potential to meet the growing demand for fish from the increasing population. At present, aquaculture production accounts for about one‐third of the total fish production in Bangladesh. This paper examines the impact of an aquaculture development project in Bangladesh on food security, with particular emphasis on the poor. The analysis shows a positive impact of aquaculture development on employment, income and consumption. A number of implications for policy in areas that might strengthen these outcomes are discussed and recommendations are presented.     

Effects of feeding levels on growth performance,feed utilization,body composition and apparent digestibility coefficients of nutrients for juvenile Chinese sucker,Myxocyprinus asiaticus

An experiment was conducted to determine effects of feeding levels on growth performance, feed utilization, nutrient deposition, body composition and apparent digestibility coefficients (ADCs) of nutrients for juvenile Chinese sucker (initial weight, 11.77±0.22 g). Chinese sucker were fed a practical diet from 0% (starvation) to 4.0% (at 0.5% increments) body weight (bw) day^?1 for 8 weeks. The results showed that growth performance, feed utilization, nutrient deposition, body composition and ADCs of dry matter, protein and energy were significantly (P<0.05) affected by feeding levels. Survival was the lowest for the starvation group. Final mean body weight, growth rate, thermal‐unit growth coefficient (TGC) increased with feeding rate from 0% to 3.0% bw day^?1 (P<0.05) and showed no significant differences above the level (P>0.05). Feed conversion rate was significantly lower at a feeding level of 2.5% bw day^?1 than above and below the level (P<0.05). Protein efficiency ratio was markedly highest at the 2.5% bw day^?1 ration level (P<0.05). Fish fed at the feeding level (1.0% bw day^?1), which represented a maintenance ration (energy gain was less than 2.27 kJ fish^?1 day^?1), showed positive protein deposition but negative lipid deposition. This indicates that fish fed a maintenance ration mobilize body lipid reserve to support protein deposition. Lipid contents of whole body, muscle and liver increased with increasing feeding rates from 0.5% to 3.0% bw day^?1 and showed no significant differences above the level (P>0.05). Protein contents of whole‐body composition increased with feeding rate from 0.5 to 3.0% bw day^?1 (P<0.05) and showed no significant differences above the level (P>0.05), whereas muscle and liver remained relatively stable with the different ration amount with the exception of fish fed a ration of 0.5% bw day^?1, at which Chinese sucker possessed significantly lower body protein concentration (P<0.05). The ADCs of dry matter, protein and energy decreased with increasing feeding levels from 0.5% to 3.0% bw day^?1 and then remained relatively constant over the level. Based on the broken‐line regression analysis using WG data, the optimum and maintenance feeding levels for Chinese sucker were 3.10% bw day^?1 and 0.45% bw day^?1 respectively.     

Haematologic and immunologic parameters of bullfrogs,Lithobates catesbeianus,fed probiotics

The effects of two probiotics (P₁–Lactobacillus acidophilus, Bifidobacterium bifidum and Enterococcus faecium and P₂–Bacillus subtilis) supplemented to commercial feed (40% crude protein) on the haematological and immunological parameters of the bullfrog Lithobates catesbeianus were studied. Two doses of each probiotic (5 and 10 g kg^?1 of food) were added to the diets and fed to frogs, totalling five treatments over 112 days. Haematological analyses consisted of total and differential leucocyte counts, erythrocyte and thrombocyte counts, haematocrit, haemoglobin levels and RBC indices (mean corpuscular volume, mean corpuscular haemoglobin – and mean corpuscular haemoglobin concentration) and the immunological parameters included phagocytic capacity and phagocytic index of peritoneal phagocytes. The results showed that the probiotics did not significantly influence any of the haematological parameters measured. However, immunological assays showed that the probiotics had an immunostimulating effect. The greatest effects were seen with probiotic P₁ fed at a dose of 10 g kg^?1 of diet and probiotic P₂ fed at 5 g kg^?1 of diet.     

Degradation and effect of hydrogen peroxide in small‐scale recirculation aquaculture system biofilters

From an environmental point of view, hydrogen peroxide (HP) has beneficial attributes compared with other disinfectants in terms of its ready degradation and neutral by‐products. The rapid degradation of HP can, however, cause difficulties with regard to safe and efficient water treatment when applied in different systems. In this study, we investigated the degradation kinetics of HP in biofilters from water recirculating aquaculture systems (RAS). The potential effect of HP on the nitrification process in the biofilters was also examined. Biofilter elements from two different pilot‐scale RAS were exposed to various HP treatments in batch experiments, and the HP concentration was found to follow an exponential decay. The biofilter ammonia and nitrite oxidation processes showed quick recuperation after exposure to a single dose of HP up to 30 mg L^?1. An average HP concentration of 10–13 mg L^?1 maintained over 3 h had a moderate inhibitory effect on the biofilter elements from one of the RAS with relatively high organic loading, while the nitrification was severely inhibited in the pilot‐scale biofilters from the other RAS with a relatively low organic loading. A pilot‐scale RAS, equipped with two biofilter units, both a moving‐bed (Biomedia) and a fixed‐bed (BIO‐BLOK^®) biofilter, was subjected to an average HP concentration of ～12 mg L^?1 for 3 h. The ammonium‐ and nitrite‐degrading efficiencies of both the Biomedia and the BIO‐BLOK^® filters were drastically reduced. The filters had not reverted to pre‐HP exposure efficiency after 24 h, suggesting a possible long‐term impact on the biofilters.     

Accumulation of heavy metals and total phosphorus in intensive aquatic farm sediments: comparison of tilapia Oreochromis niloticus×Oreochromis aureu,Asian seabass Lates calcarifer and white shrimp Litopenaeus vannamei farms

This paper compares and discusses the accumulation of eight heavy metals (Cd, Co, Cr, Cu, Pb, Fe, Mn and Zn) and total phosphorus (TP) in surface sediments from five intensive farms of tilapia Oreochromis niloticus×Oreochromis aureu, Asian seabass Lates calcarifer and white shrimp Litopenaeus vannamei (n=75). Results indicate that the sediments were significantly contaminated by Cd, Co, Cr, Cu, Pb, Fe, Mn and Zn as well as P. The mean concentrations of Cd (0.47 mg kg^?1), Co (2.25 mg kg^?1), Cu (31.56 mg kg^?1), Pb (23.45 mg kg^?1), Fe (1.15%), Mn (145.5 mg kg^?1), Zn (41.5 mg kg^?1) and TP (750.69 mg kg^?1) in tilapia farm surface sediments were significantly lower than the levels observed in Asian seabass and white shrimp farm surface sediments, where the concentrations were, respectively, Cd – 2.69 and 2.35 mg kg^?1, Co – 17.66 and 15.22 mg kg^?1, Cu – 116.84 and 110.03 mg kg^?1, Pb – 38.5 and 33.26 mg kg^?1, Fe – 3.4% and 3.31%, Mn – 853.61 and 728.5 mg kg^?1, Zn – 105.21 and 83.92 mg kg^?1 and TP – 1445.63 and 1069.8 mg kg^?1. The heavy metal content of the sediments follow the order: Asian sea bass>white shrimp>tilapia. Cadmium and Cu in Asian seabass and white shrimp farm sediments would pose a major potential risk. Further, the sediment is highly enriched by Fe, P, Mn and Co.     

Parentage assignment in Haliotis midae L.: a precursor to future genetic enhancement programmes for South African abalone

The establishment and evaluation of family lines using pedigree information provides an advanced understanding of the variability that exists for complex, economically valuable traits and is a necessary step in the execution of an effective breeding programme. The aim of this study was to assign parentage to mass‐spawned Haliotis midae juveniles using species‐specific microsatellite markers. Screening of wild abalone individuals revealed that the nine loci selected complied with the minimum requirements for parentage analyses: a null allele frequency <5% as well as a high number and frequency of alleles per locus. A total of 598 individuals were genotyped (198 breeding individuals and 400 F1 progeny) from two farms, with parentage results yielding 91% and 90% successful assignment for Farms A and B respectively. This study, therefore, provided the necessary pedigree information required for controlled breeding of individual adult abalone and indicated the usefulness of the panel of microsatellite markers selected for parentage assignment.     

Effects of graded levels of dietary myo‐inositol on non‐specific immune and specific immune parameters in juvenile Jian carp (Cyprinus carpio var. Jian)

The aim of this study was to evaluate the effects of myo‐inositol (MI) on non‐specific immune and specific immune defence in fish. A total of 1050 Jian carp (Cyprinus carpio var. Jian) (22.28±0.07 g) were randomly distributed into seven groups, of three replicates each, of feeding diets containing graded levels of MI (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg MI kg^?1 diet). After a 60‐day growth trial, an infectious trial was conducted by injection of Aeromonas hydrophila for 17 days. Results showed that the red blood cell (RBC) and the white blood cell count were significantly increased with increasing MI levels up to 535.8 mg kg^?1 diet (P<0.05). The spleen index showed a tendency similar to RBC, whereas the head kidney index showed the inverse pattern (P<0.05). The phagocytic activity of leucocytes, haemagglutination titre, lysozyme activity, anti‐A. hydrophila antibody titre and immunoglobulin M, after being injected with A. hydrophila, were all improved with an increase in the MI levels up to 232.7–687.3 mg kg^?1 diet respectively (P<0.05). Myo‐inositol did not influence serum acid phosphatase activity and total iron‐binding capacity (P>0.05). These results suggested that MI could enhance non‐specific immune and specific immune responses in fish.     

Protein lipid ratio for the growth and survival of juvenile crayfish Procambarus acanthophorus (Hobbs 1972) reared under controlled conditions

The influence of dietary protein/lipid levels on growth and survival in juvenile crayfish (Procambarus acanthophorus) was evaluated during a 12‐week nutritional trial. Twenty experimental diets were formulated containing different protein (200, 250, 300, 350 and 400 g kg^?1) and lipid (60, 80, 100 and 120 g kg^?1) levels. A bifactorial model (5 × 4) was used with three replicates and 15 crayfish (0.014±0.006 g) per replicate, in a recirculation system with 60–15 L rectangular tanks and a biological filter, the culture conditions were a photoperiod of 12:12 h L:D and temperature 24.7±1.0 °C. Total survival ranged from 66.6% to 86.6%, with no differences attributed to treatments. Dietary protein levels had a significant effect on growth gain and nutritional efficiency; in contrast, lipid levels had no effect on juvenile performance. The 250/120 (protein/lipid) treatment promoted the most efficient growth (final weight: 3.09 g, weight gain: 21 995%, specific growth rate: 3.35% day^?1); the less efficient growth was observed in juveniles fed with 400 g kg^?1 protein diets. The quadratic regression model indicated 279 g kg^?1 as the optimal protein level for crayfish growth, while levels between 211 and 232 g kg^?1 could minimize the feeding costs without affecting growth.     

Effect of replacing soybean meal with canola meal on growth,feed utilization and haematological indices of juvenile hybrid tilapia,Oreochromis niloticus×Oreochromis aureus

An 8‐week feeding trial was conducted to evaluate the effects of replacing soybean meal (SBM) with canola meal (CM) on growth, feed utilization, body composition and haematological indices of juvenile hybrid tilapia (Oreochromis niloticus×Oreochromis aureus). Six isonitrogenous diets containing graded levels of CM (0, 95, 190, 285, 380 and 634 g kg^?1 of diet corresponding to 0%, 15%, 30%, 45%, 60% and 100%, respectively, of protein from SBM) to replace SBM on an equal protein basis were fed to triplicate groups of juvenile fish (initial weight=6.3 g). The results indicated that up to 30% of SBM could be replaced by CM without causing a significant reduction in growth performance. Fish fed with diets in which CM replaced over 45% of SBM had a significantly lower protein efficiency ratio and a significantly higher feed conversion ratio than fish fed with other diets. The apparent digestibility coefficients (ADC) of dry matter, protein and phosphorus were lowest for fish fed the CM100 diet. Significant differences in haemoglobin, haematocrit and white blood cell concentration were found in fish fed diets with different CM levels. It is concluded that up to 19.02% CM can be used to replace 30% of SBM in diets for juvenile hybrid tilapia without compromising growth, feed conversion and protein utilization.