Effects of the timing of initial feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae

The effects of delayed first feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae were examined under controlled conditions. Morphometric characters [yolk-sac volume, oil globule volume, head depth ( H D ), body depth ( B D ), eye diameter ( E D ), musculature height ( M H ), mouth diameter ( M D ) and total length ( L T )], body mass ( M ), specific growth rate ( S GR ) and survival were evaluated under different first-feeding time (2, 3, 4 and 5 days after hatching). Larvae began to feed exogenously at 2 days after hatching (DAH) and the point of no return ( P NR ) occurred between 5 and 6 DAH at 23° C, range ±1·0° C. The yolk volume of larvae first-fed at 2 days had a significant difference compared with that of larvae first-fed at 3, 4 and 5 days on 3 and 4 DAH. The larvae first-fed at 2 days achieved comparatively better growth performance than that of 3, 4 and 5 days. On 5 DAH, all morphometric characters had significant differences between 2 and 5 days and 2 and 4 days initial feeding, respectively. Total mortality was recorded on 9 DAH for the larvae first-fed at 5 days. On 12 DAH, significant differences were observed between 2 and 4 days and 3 and 4 days initial feeding for all morphometric characters. From 16 DAH to the end of experiment, all growth variables of the larvae first-fed at 2 days were significantly higher than those in other treatments. The S GR (2–9 DAH) first-fed at 2 and 3 days were significantly higher than 4 and 5 day treatments, and the S GR (9–16 DAH) first-fed at 2 days was significantly higher than 3 and 4 day treatments. There was no significant difference, however, of S GR (16–28 DAH) among treatments. Survival rate was significantly higher at 2 days initial feeding (27·42%) when compared with 3 (15·96%) and 4 days (7·92%) initial feeding at the end of experiment. The present study suggests that the first feeding of S. scherzeri larvae should be initiated at 2 days after hatching for achieving good growth and survival.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78713/1/j.1095-8649.2009.02328.x.pd

Feeding behaviour and digestion physiology in larval fish – current knowledge and gaps and bottlenecks in research

Food uptake follows rules defined by feeding behaviour that determines the kind and quantity of food ingested by fish larvae as well as how live prey and food particles are detected, captured and ingested. Feeding success depends on the progressive development of anatomical characteristics and physiological functions and on the availability of suitable food items throughout larval development. The fish larval stages present eco-morpho-physiological features very different from adults and differ from one species to another. The organoleptic properties, dimensions, detectability, movements characteristics and buoyancy of food items are all crucial features that should be considered, but is often ignored, in feeding regimes. Ontogenetic changes in digestive function lead to limitations in the ability to process certain feedstuffs. There is still a lack of knowledge about the digestion and absorption of various nutrients and about the ontogeny of basic physiological mechanisms in fish larvae, including how they are affected by genetic, dietary and environmental factors. The neural and hormonal regulation of the digestive process and of appetite is critical for optimizing digestion. These processes are still poorly described in fish larvae and attempts to develop optimal feeding regimes are often still on a ‘trial and error’ basis. A holistic understanding of feeding ecology and digestive functions is important for designing diets for fish larvae and the adaptation of rearing conditions to meet requirements for the best presentation of prey and microdiets, and their optimal ingestion, digestion and absorption. More research that targets gaps in our knowledge should advance larval rearing

Effect of shelter acclimation on the post-release movement and putative predation mortality of hatchery-reared black-spot tuskfish Choerodon schoenleinii, determined by acoustic telemetry

In this study, the effect of shelter acclimation on the post-release movement and putative predation mortality of hatchery-reared black-spot tuskfish Choerodon schoenleinii was examined using acoustic telemetry. We acclimated four 1-year-old fish to shelters in cages before release and compared their movements with six nonacclimated fish. Since it was not possible to compare the behavioral pattern between the former and the latter fish due to the short periods the latter fish were available to be monitored, we also compared their movements with those of large nonacclimated fish that were less likely to be preyed upon. Sixty-seven percent of the nonacclimated fish showed atypical movements before the signals ceased to be detected, a pattern that suggested a predation event had occurred, whereas none of the acclimated and large nonacclimated fish showed the atypical movements. In addition, the probability of detection cessation was about 13 times lower in the acclimated than nonacclimated fish. The signal detection patterns suggest that the acclimated fish utilized night-time shelters from the first night after release, while the large nonacclimated fish started to utilize shelters several days after release. Therefore, it is likely that the shelter acclimation enhanced the shelter utilization by tuskfish, possibly decreasing post-release predation mortality

Mating and nesting behavior of hawksbill turtle (Eretmochelys imbricata) in captivity

December 13-14, 2006, Siam City Hotel, Bangkok, ThailandWe previously reported that two long-term reared mature females laid a total number of 894 eggs during a total of 7 nesting times. However, we did not elaborate the relationship between mating and nesting behavior. In the present study, we investigated the relationship between mating and nesting behavior in captivity. Details of the mating and nesting behavior were monitored since December 2005 by using four highly sensitive cameras continuously throughout day and night. Two cameras were fixed on the edge of the tank observation window and two cameras on the upper side tank wall connected to an artificial sand nesting bed. Rearing methods and the feeding protocol were same as the previous report (Shimizu et al., 2006). One mature male and three mature females were used for the present study. These turtles were the same turtles used for the previous study (Shimizu et al., 2006). After the nesting periods in 2004, the females did not mate with the male and did not lay eggs in 2005. One time mating was first observed after the start of camera observations in December 2005 in the two females during April to May. Shelled eggs were first observed between 13 and 18 days after mating. Thereafter the first laying was observed between 24 and 33 days after mating

A new technique for monitoring grazing behavior of Hawksbill turtles (Eretmochelys imbricata) using acceleration data loggers

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-15, 2004, Imperial Tara Hotel, Bangkok, ThailandGrazing behavior of sea turtles is important to understand their behavioral ecology. However, there is a shortage of effective techniques available for monitoring the grazing behavior accurately over a long period. In this study, the grazing behavior of hawksbill turtles (Eretmochelys imbricata) was monitored with acceleration data loggers which recorded depth, temperature, and accelerations in two axes. A Juvenile hawksbill turtle was attached with two acceleration data loggers on both head and carapace. During the experiment, we recorded the behavior of turtles on the underwater digital video camera. Their behaviors were distinguished into four patterns through the acceleration profiles and the underwater observation as follows; resting, swimming, grazing and breathing. The new technique can clarify when and where turtles graze quantitatively as well as time allocation of their behavior patterns

Genetic diversity of the green turtle nesting populations in Yaeyama Archipelago, Japan

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandPatterns of mitochondrial DNA (mtDNA) variation were used to analyze the genetic diversity and population genetic structure of green turtle (Chelonia mydas) populations in Yaeyama Archipelago, southwestern Japan. Six mtDNA haplotypes were observed among 42 nesting green turtles. Nucleotide diversities at Yaeyama populations are higher than other sea turtle populations, reflecting all rookeries are comprised of a mixture of divergent haplotypes. Because genetic diversity is believed to represent the ability of populations to adapt or respond to environmental changes, it is important to protect Yaeyama nesting colonies for conserving this endangered species

Wild versus head-started hawksbill turtles Eretmochelys imbricata: post-release behavior and feeding adaptions

To ensure the success of reintroduction programs, it is important to monitor the post-release behavior and survival of released animals. In this study, the post-release movement and behavior of 5 wild and 5 head-started hawksbill turtles Eretmochelys imbricata were monitored using ultrasonic telemetry. Their dispersal directions and recaptures may indicate that wild turtles perform homing migrations. However, the head-started turtles showed non-uniform patterns in dispersal movements. Four head-started turtles moved out of the monitoring area in various directions, whereas one turtle stayed within the monitoring area for approx. 10 mo. These results might indicate that head-started turtles wander aimlessly in their new surroundings. Signal reception patterns indicated that wild turtles were active in the daytime and rested under the coral at night. Although the head-started turtles also rest at night, their resting places did not seem to be sheltered from hazardous sea conditions or adequate for efficient resting. Therefore, head-started hawksbill turtles appear to need pre-release training such as exposure to structures or ledges in the rearing tank so they can utilize similar structures in the wild for shelter during rest periods and maximize their dive duration by employing these as a roof to counteract the positive buoyant effect of inhaled air. Prey analysis of a head-started turtle captured incidentally demonstrates that these turtles can make feeding adaptations to adjust to the natural environment. These findings provide constructive information for the implementation and improvement of head-start programs

Dispersal processes of head-started hawksbill turtles (Eretmochelys imbricate) in the Yaeyama Islands waters, Okinawa, Japan

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-14, 2005, Siam City Hotel, Bangkok, ThailandBehaviors of five head-started hawksbill turtles (Eretmochelys imbricata) attached with ultrasonic transmitters were monitored using 12 ultrasonic receivers set up along the reef edge. The head-started turtles were reared for two years in the Yaeyama Station, National Center for Stock Enhancement. Four of five head-started turtles moved out of the monitoring area, but their movements are not linearly. The duration the four head-started ones stayed in the monitoring area ranged from 4 to 14 days. All of the head-started turtles had a circadian rhythm to their behaviors. The other head-started turtle stayed around the release point for 88 days until it was recaptured by a fisherman. There was not much difference in diving depth between the head-started and the wild turtles reported by other sites. These results indicate that the head-started turtles tend to wander aimlessly in the natural environment, although they have natures of a circadian rhythm and diving technique

Diel behavioral pattern of hatchery-reared black-spot tuskfish determined by acoustic telemetry in the natural environment and video observation in a fish tank

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandDiel behavioral pattern of hatchery-reared black-spot tuskfish was examined by acoustic telemetry in the natural environment and video observation in a fish tank. Nine tuskfish were monitored using acoustic telemetry for 150 days; five fish were observed in a fish tank for 2 days. In the acoustic telemetry tracking, tuskfish moved horizontally and vertically during the day; they stayed still at night. The tuskfish tended to utilize depths near the bottom both during the day and night. In the video observation, the tuskfish tended to move actively and sweep sand at bottom during the day; they tended to stay still in the crater they made during the night. These results indicated that tuskfish might make their night-time resting house by sweeping sand near structures and forage benthic preys during the day, and rest in the resting house at night

Successful spontaneous nesting of the hawksbill turtle (Eretmochelys imbricate) at Yaeyama Station, National Center for Stock Enhancement, Japan

Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society InfrastructureDecember 13-14, 2005, Siam City Hotel, Bangkok, ThailandWith a view to the conservation of the natural stock of the hawksbill turtle (Eretmochelys imbricata), we carried out studies on the propagation techniques of this species. This paper deals with the spontaneous nesting of this species under rearing conditions. Adult turtles that were captured off Ishigaki Island between 1999 and 2002 were brought to the center by licensed fishermen. One adult male and three mature females were selected from 29 turtles and they were stocked in a 250kL tank that was connected to a sandy beach for nesting. The females were examined by ultrasonography throughout experimental period. The mean diameter of the follicles ranged from 1.4 - 1.7 cm from January to April; and gradually increased to 3.0 cm from which shelled eggs were laid. The shelled eggs were first observed on 2nd June 2004, but were not observed after September. In contrast, non nesting individuals had not possessed shelled eggs during the experimental period. These results indicate that the formation of shelled eggs is an indicator of nesting. The first nesting was observed on 7th June, with a total of 7 nestlings observed until September. A total of 894 eggs were obtained from two females