Laboratory investigation of daily food intake and gut evacuation in larvae of African catfish Clarias gariepinus under different feeding conditions

Abstract Temporary accumulation of ascorbic acid 2-sulfate (AAS) was measured to estimate food intake and gut evacuation in larvae of African catfish. Fish larvae were fed decapsulated cysts of Artemia containing AAS. In a first experiment it was found that no biosynthesis of AAS occurs in the larvae of this species. In a second experiment, the gut contents of the fish larvae fed were calculated as they changed during development. In a third experiment, the gut evacuation rate of fish larvae was determined during continuous and discontinuous feeding regimes in the first five days after the start of exogenous feeding. Food consumption by catfish larvae increased from 46.5% of their body dry weight (BDW) on day 1 after the start of exogenous feeding to 53.8% BDW on day 3. Thereafter, food consumption decreased to 27.8% BDW on day 5. A similar pattern was observed for gut evacuation, which increased during the first days of exogenous feeding and decreased as fish growth continued. The rate of gut evacuation in a continuous feeding regime was significantly higher (P <0.05) than that under discontinuous feeding. On day 1 post-hatch and 7 h after first food ingestion the fish larvae evacuated 87% of the food in continuous feeding compared with 43% under discontinuous feeding. It was found that gut emptying differs during larval development. Under continuous feeding, on days 1 and 3 post-hatch and 11 h after the first meal 90% of the food was evacuated compared with 71% evacuated on day 5. The advantages and limitations of the AAS method for estimation of food consumption by fish larvae are discussed

Effects of different photoperiods on the survival and growth of beluga sturgeon (huso huso) larvae

Effect of different photoperiodic regimes was evaluated on growth performance and survival rate of the Beluga (Huso huso) prelarvae and larvae. Newly hatched prelarvae were stored in 5 round fiberglass 500‑L tank with different photoperiod (24L:00D, 18L:06D, 12L:12D, 06L:18 D, 00L:24D) till 50 days post hatch with three replicates. Light intensity was 200 lux during the experiment. Feeding was started from 8 days post hatch using live artemia nauplii. Higher total length, survival rates and lower body area, yolk area for beluga prelarvae obtained in long light photoperiods (24L:00D, 18L:06D). Also, higher growth parameters of the beluga larvae observed in long light photoperiods while different photoperiods had no effect on survival rate. The present study indicated that growth performance and survival rates of larvae are significantly influenced by photoperiod. The photoperiod 18L:06D resulted in the best growth performance and survival rate during early development of the beluga

Epidemiology of strongyle nematode infections and first report of benzimidazole resistance in Haemonchus contortus in goats in South Darfur State, Sudan

Background Since pastoralists in South Darfur, Sudan, had complained about lack of albendazole (ABZ) efficacy to control nematodes in goats, the frequency of infection with gastrointestinal helminths was studied before in vivo faecal egg count reduction tests (FECRT) were conducted using ABZ orally either at the dose recommended for sheep, 5 mg/kg body weight (bw) or at 10 mg/kg bw. Experiments included goats naturally infected with gastrointestinal nematodes or experimentally infected with local Haemonchus contortus isolates. Three study areas (Nyala, Beleil and Kass) were visited in autumn or winter. Results Out of 478 screened goats, 82.4% were infected with gastrointestinal helminths and 82% were shedding eggs of strongyle nematodes with 90% of the strongyle larvae representing Haemonchus spp. A FECRT using naturally infected goats (n = 225: 71 untreated, 104 and 50 treated with 5 and 10 mg ABZ/kg bw, respectively) detected reduced ABZ efficacy in Nyala and Kass. Paired and unpaired FECRT calculations detected reductions of 72–92% with samples taken at 8 days post treatment with 5 mg ABZ/kg bw and of 85–94% with 10 mg ABZ/kg bw. The FECRT based on day 14 post treatment samples showed reductions of 69–77% with 5 mg/kg and of 75–87% with 10 mg ABZ/kg bw. In Beleil, ABZ efficacy was 95%. In the egg hatch test EC50 values for Nyala and Kass ranged from 0.12–0.24 μg thiabendazole/ml, corresponding to benzimidazole resistant phenotypes. Only Haemonchus spp. larvae were present after treatments in coprocultures. When the efficacy was evaluated experimentally using isolates of H. contortus from Nyala and Kass, the 5 mg ABZ/kg dose revealed reductions of 76–78% on day 8 and of 62–70% on day 14 with the unpaired method. Using 10 mg ABZ/kg, the FECR was still only 77–82%. Conclusions Both, in vivo and in vitro methods detected resistant H. contortus populations in goats from South Darfur State. The time point 14 days post treatment was more sensitive for detection of ABZ resistance than 8 days post treatment. This is the first report on the occurrence of anthelmintic resistance in Sudan confirming that anthelmintic resistance selection is occurring in African subsistence farming systems

Jungle perch Kuhlia rupestris fingerling production manual

This manual consists of written descriptions of jungle perch Kuhlia rupestris production and video material to demonstrate each of the key production steps. Video links are at the end of each major written section in the document. To activate the link use ctrl click. The videos enhance the instructive ability of this manual. The keys to producing jungle perch are: - maintaining broodstock in freshwater or low salinity water less than 5 ppt - spawning fish in full seawater at 28C - incubating eggs in full seawater. Salinities must not be less than 32 ppt - ensuring that first feed jungle perch larvae have an adequate supply of copepod nauplii - rearing larvae in full seawater under bright light - use of gentle aeration in tanks - postponing spawns until adequate densities of copepod nauplii are present in ponds - sustaining copepod blooms in ponds for at least 20 days - avoiding use of paddlewheels in ponds - supplementary feeding with Artemia salina and weaning diets from 20 days after hatch - harvesting of fingerlings or fry after they are 25-30 mm in length (50 to 60 days post hatch) - covering tanks of fingerlings with 5 mm mesh and submerging freshwater inlets to prevent jumping

Jungle perch Kuhlia rupestris fingerling production manual

This manual consists of written descriptions of jungle perch Kuhlia rupestris production and video material to demonstrate each of the key production steps. Video links are at the end of each major written section in the document. To activate the link use ctrl click. The videos enhance the instructive ability of this manual. The keys to producing jungle perch are: - maintaining broodstock in freshwater or low salinity water less than 5 ppt - spawning fish in full seawater at 28C - incubating eggs in full seawater. Salinities must not be less than 32 ppt - ensuring that first feed jungle perch larvae have an adequate supply of copepod nauplii - rearing larvae in full seawater under bright light - use of gentle aeration in tanks - postponing spawns until adequate densities of copepod nauplii are present in ponds - sustaining copepod blooms in ponds for at least 20 days - avoiding use of paddlewheels in ponds - supplementary feeding with Artemia salina and weaning diets from 20 days after hatch - harvesting of fingerlings or fry after they are 25-30 mm in length (50 to 60 days post hatch) - covering tanks of fingerlings with 5 mm mesh and submerging freshwater inlets to prevent jumping

Development of Morphology in Hatchery-Reared Rutilus Frisii Kutum Larvae

Most fish are poorly developed at hatching. They undergo important functional and morphological changes during the early larval period. This study was conducted to monitor the morphological changes of Caspian kutum Rutilus frisii kutum larvae in early life stages. Fertilized kutum eggs were incubated at 16-19ºC in 8 l glass incubators for 9.5 days. At first feeding (3 days after hatch) larvae were fed two times per day with egg yolk for 5 days, and then Artemia nauplii and egg yolk until day 30. The juveniles were then transferred to an outdoor fish hapa nets and further reared until day 60. Larval development, growth, and some morphological changes were described from day 0 to end of experiment. The results showed that there were 3 main stages and 18 sub-stages of ontogenetic development in Caspian kutum from hatching to juvenile stage. The most important change in these stages was change from endogenous to exogenous feeding. During post hatch development, the various organs gradually differentiated and became identifiable

Parental effects on early life history traits of haddock Melanogrammus aeglefinus

Gametes from five male and three female haddock ( Melanogrammus aeglefinus ) were crossed to produce 15 half-sibling families that were used to evaluate potential parental contributions to early life history variability. Larval morphology at 0 and 5 days post-hatch (dph) and time to starvation in the absence of food were examined. Maternal influences on larval standard length and yolk area were significant at 0 and 5 dph. Paternal effects on larval standard length were significant at 0 and 5 dph, whereas paternal effects on yolk area were only significant at 5 dph. Larval eye diameter was influenced by maternity at day 0 post-hatch and by both maternity and paternity at 5 dph. Myotome height of larvae was subject to maternal and paternal influences at 0 and 5 dph. Growth rate was significantly influenced by both paternity and maternity. Yolk utilization efficiency was significantly influenced by parental interaction, while the time taken for larvae to die in the absence of food was affected only by maternity. Results of this study not only confirm the importance of female contributions to larval development but also indicate a paternal influence on the development and the early life history success of marine fish

Specific Dynamic Action, Growth and Development in Larval Atlantic Cod, Gadus Morhua

The larval stage of marine fish is a period of rapid growth and development. Atlantic cod (Gadus morhua) are approximately 4-5 rnm in length upon hatch and feed endogenously from their yolk sac for the first week. After this time, larval cod must successfully capture live prey to survive and to fuel high growth rates of greater than 10%d . Previous studies have found that during exogenous feeding and at growth rates greater than 8%d1 larvae experience what appears to be cost free growth, where mass specific metabolic rate does not decrease with increasing mass. Due to size and condition constraints involved in working with larval marine fish, few data exist on the metabolism of early larval growth. This study was done using microcalorimetry to identify specific dynamic action (SDA) which represents the cost of feeding, digestion, and protein assimilation (growth) in larval cod. Cod were used in the experiments only after the yolk sac was completely utilized, and the larvae were feeding exogenously. This study was the first to record changes in metabolic rates as a function of feeding in larval fish using a microcalorimeter. Growth rates for two populations (Rhode Island and Newfoundland) of Atlantic cod were measured and ranged from 6.9%d-\u27 to 13. l%dml, showing that larvae grew well under culture conditions. After comparing mean growth rates between the two populations and finding them to be significantly different, only Newfoundland cod were used in the experiments to measure SDA. Using a ThermometricO LKB 2277 microcalorimeter (TAM) the total heat output of larval cod fiom 10 - 40 days post hatch was determined under two different feeding conditions. Two cod of the same age (days post hatch) were placed concurrently into the microcalorimeter in one of two channels. One cod larva was left unfed for at least 12 hours prior to the experiment (unfed) while the other was fed to satiation immediately before the experiment was run (fed). TAM measurements showed that for the first 30 days post hatch (dph), both fed and unfed larval cod showed increases in mean heat output on a daily basis. During this time fed larvae had a significantly higher average heat output than unfed larvae. From day 30 through 40 post hatch, fed larvae were observed to have a lower mean daily heat output when compared to unfed larvae. This change in mean daily heat output may be attributed to factors involved in the transformation stage of the larvae to the juvenile stage such as more efficient digestion and increased swimming and searching activity

The effects of osmotic challenges : involvement of ion transport proteins NKA, NKCC, and CFTR in the Gulf killifish, Fundulus grandis

This dissertation investigated the cellular and molecular basis of osmoregulation in developing and adult Gulf killifish, Fundulus grandis, acclimated to salinities ranging from fresh water to sea water. In chapter 2, F. grandis embryos were reared in 0.1, 5, and 32 ppt water from 2 days (d) post fertilization until late embryogenesis. There were no discernable differences among salinities in the morphology of osmoregulatory organs, including the pharyngeal arches, digestive tract, or kidney. The localization and abundance of Na+/K+ ATPase (NKA), Na+/K+/2Cl- cotransporter (NKCC), and the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) on the external surfaces of these tissues support a role in osmoregulatory as early as prior to hatch. In addition, F. grandis larvae were exposed from hatch to 0.1, 5, and 32 ppt water until 6 weeks post hatch (wph). Differential localization of NKCC and CFTR during osmotic challenges indicated putative altered functions of the intestine and gills, but not of the kidney in larval F. grandis. In Chapter 3, adult F. grandis were acutely transferred from 5 ppt water to 0.1, 1, and 5 ppt water for 7 d, or were acclimated to 0.1 ppt water then acutely transferred to 0.1 and 32 ppt water for 7 d. The mRNA and protein levels of NKA, NKCC, and CFTR in the intestine were differentially affected by the hypo- or hyperosmotic challenges. Localization of transport proteins suggested differences in intestine function associated with salinity acclimation. The anterior and posterior intestine may function in HCO3- or Cl- secretion during exposure to 0.1 ppt water; the anterior intestine from 32 ppt acclimated fish may facilitate both Cl- and water absorption; and the posterior intestine during exposure to 32 ppt water may facilitate HCO3- or Cl- secretion. In chapter 4, the roles of these proteins in the anterior intestine of F. grandis were assessed using an electrophysiological approach coupled with pharmacological inhibition of transporters. A high apical CFTR activity in the anterior intestine during acclimation in fresh water was observed. In conclusion, salinity acclimation affected the possible functions of osmoregulatory tissues of larval F. grandis, as well as the putative functions in ion/water regulation in the intestine of adult F. grandis

Methods for Capturing, Marking, and Estimating Survival of Northern Bobwhite Chicks (Poster Abstract)

Lack of techniques to capture, mark, and observe chicks from hatch to fall has hindered our ability to understand this critical life stage of northern bobwhite (Colinus virginianus) and other galliforms. We present 2 methods for capturing wild, free-ranging northern bobwhite chicks associated with a radiomarked adult and demonstrate application of capture-recapture estimators. Both capture techniques involve monitoring radiomarked adults, locating nests, determining date of hatch, and then locating roosting adults with broods prior to sunrise during the pre-flight period (1–12 days post-hatch). The first technique involves erecting a temporary circular fence around the roosting radio-marked bird and brood, securing the edges with dirt, and systematically clearing all vegetation and ground debris until chicks are captured. The second technique involves placing a temporary fence in a ‘‘V’’ formation with a small mesh funnel trap placed at the apex. Birds are then ‘‘corralled’’ into the funnel trap. We used both methods during the breeding seasons of 1997–99. Overall, we captured 762 chicks from 137 broods. Of 131 capture attempts using the ring method, 18.3% (n = 24) were complete failures, 13.7% (n = 18) resulted in partial capture, whereas 68% (n = 89) resulted in complete capture. Using the funnel method, 22.2% (n = 2) of attempts were complete failures, 22.2% (n = 2) resulted in partial captures, and 55.6% (n = 5) resulted in complete brood capture. Captured chicks can be permanently and uniquely marked using monel patagial wing bands. We demonstrate application of capture-recapture models in program MARK to estimate chick survival from hatch to recruitment in the fall population (Oct 1)