Now showing items 1-8 of 8

    • Article

      Effects of Chlorella-feeding on larval milkfish, Chanos chanos, as evidenced by histological monitoring 

      H Segner, P Burkhardt, EM Avila, V Storch & JV Juario - Aquaculture, 1987 - Elsevier
      Milkfish, Chanos chanos, larvae were found to suffer 100% mortality within 6 days of feeding when reared on Chlorella sp. According to the liver ultrastructure, Chlorella-fed fish underwent starvation. Likewise, no signs of lipid absorption were observed in the intestine of Chlorella-fed larvae. On the other hand, Chlorella-related histological alterations of the enterocytes in the anterior part of the intestine were different from starvation-related alterations. It is concluded that Chlorella-feeding creates a starvation situation for larval milkfish, but the early losses with this diet are due to an additional stress specifically introduced by Chlorella-feeding.
    • Article

      Hatchery rearing of sea bass Lates calcarifer Bloch 

      MM Parazo, DM Reyes Jr. & EM Avila - The Philippine Scientist, 1991 - Science and Technology Information Institute
      A hatchery rearing scheme for sea bass (Lates calcarifer Bloch) is described. Survival rate from hatching (d0) to harvest (d30) was 34%. Feeding sea bass fry with Chlorella-fed or Selco-enriched instar II Artemia from d19 to d23 resulted in similar survival rates (74%), total length (8.2 and 8.9 mm) and weight (8.9 and 12.1 mg) at d30. Although sea bass fry fed 2.5, 5 or 10 Artemia/ml/day from d14 to d20 exhibited similar survival rates (73-93%), fish were significantly larger as feed density increased (7.1, 8.2, 9.8 mm total length and 2.4, 4.3, 9.7 mg wet weight, respectively). The significance of this study lies in providing technical information on artificial production of sea bass fry.
    • Conference paper

      Histopathology of chlorella-feeding in larval milkfish, Chanos chanos 

      Unicellular algae, particularly Chlorella, are widely used as starter feeds for marine finfish larvae. However, milk fish larvae when reared on Chlorella sp., suffered morality up to 100% within the first days of feeding (Fig. 1). Morality induced by Chlorella occurred earlier than that induced by starvation. The present Communication describes histopathological changes in liver and intestines of mlikfish larvae fed with Chlorella sp., copared with starvedor Artemia-fed fish. Feeding the larvea with Artemia for 7 days evofed (Ø 12-16 micro m) hepatocytes, with a well-developed and orderly arranged rough endoplasmic reticulum (rER). Greater amounts of glycogen were deposited. Whereas those fed with Chlorella (Fig. 2) resulted in cellular shrinkage (Ø 5-7micro m), complete absence of stored products, degeneration of rER. swelling of mitochondria and augmentation of lysosome-like structures (compare also Juario & Storch 1984). Starvation-related alterations of hepatocyte ultrastructure were essentially similar.

      The intestinal tract of milkfish larvae is subdivided into pharynx, esophagus, stomach, intestines I(making up to 70% of gut length), II(up to 20%), and III (up to 10%). Nutritional related changes were only observed in intestines I and II. In Artemia-fed specimens there was intensive lipid absorption in I (Fig. 3) and well-developed supranuclear vacuoles in II (Fig. 4). Under starvation, The first part of the intestine was characterized by partial cellular hydrops, autolyic vacuoles (Fig. 5) and a dissolution of basal labyrinth. The supranuclear vacuoles of II were reduced to smaller, electron dense inclusions (Fig. 6). Chlorells appeared partially digested in the gut. It evoked pathological intrcellular vacuolation of the epithelial cells and bizarre forms of the nuclei in I (Fig. 7). In II, changes were similar to starved larvae (fig. 8).

      The present report is another example of high moralities occurring among fish larvae reared on live feeds (compare Eckmann 1985).
    • Article

      Hormone-induced spawning and embryonic development of the rabbitfish, Siganus vermiculatus (Pisces: Siganidae) 

      EM Avila - The Philippine Scientist, 1984 - San Carlos Publications, University of San Carlos
      Induced spawning experiments were conducted on captive Siganus vermiculatus with the use of human chorionic gonadotropin (HCG APL Ayerst). The hormone was administered intramuscularly and the intraovarioan oocyte development and milt conditions of the fish were monitored by in vivo methods. Likewise, the spawning behavior and early life history of the species were observed and documented.

      Spontaneous spawnings and natural fertilization of the eggs occurred following ovulation in the fish injected with 500 IU HCG between 17 and 18 hrs after the last of a series of injections delivered at 24-hour intervals. Accelerated oocyte maturation was indicated by progressive changes in the gross morphological characters of the eggs and further thinning of milt. Dominant and aggressive behavior of the female characterized the spawning activities which commenced in the mornings.

      Newly-fertilized demersal eggs measured 0.52 ± 0.01 mm in diameter and each had a narrow perivitelline space, the yolk containing several centrally-located oil globules. Embyonic development was basically similar to that exhibited in most bony fishes. Atretic eggs retained in the body cavity averaged 0.57 ± 0.01 mm in diameter. Yolksac larvae, 1.75 ± 0.14 mm in standard length, hatched 23 to 24 hrs after fertilization in 25-25 ppt sea water at ambient temperature (25.9-28.1°C).
    • Article

      Nutrition-related histopathology of the intestine of milkfish Chanos chanos fry 

      H Segner, P Burkhardt, EM Avila, JV Juario & V Storch - Diseases of Aquatic Organisms, 1987 - Inter Research
      A histopathological study was conducted on the intestine of milkfish larvae Chanos chanos, subjected to different nutritional conditions. Newly caught milkfish fry, ca 20 d old, were starved for 7 d and and then fed with either Artemia nauplii or Chlorella sp. The latter diet, as already shown in other studies, is detrimental to young milkfish. A third, control group of fry was starved for a further 2 d. In larvae fed with Artemia, 1 to 2 h after feeding, intensive lipid absorption was noted in the first part of the intestine (Intestine I, lipid-absorbing zone, midgut). The second part of the intestine (Intestine II, hindgut) was characterized by pinocytotic activity and the presence of large supranuclear vacuoles. Food deprivation for 9 d resulted in cellular hydration, transformation of mitochondria, disturbances of the basal labyrinth and appearance of autolytic vacuoles in enterocyte cytoplasm in Intestine I, with a proximo-distal gradient of severity of enterocytic degeneration. In Intestine II, supranuclear vacuoles were replaced by dense bodies; pinocytotic activity was maintained at a reduced level. Microvilli were fragmented over the whole length of the intestine. Chlorella-fed larvae, although containing broken algae within the gut lumen, displayed no signs of nutrient absorption as detectable by electron microscopy. In Intestine I, enterocytes contained bizarre nuclei, an enhanced number of lysosomes and occasionally large intracellular vacuoles. In addition, intercellular spaces were dilated. Mitochondria appeared pale and swollen throughout the gut. Histological alterations in Intestine II were similar to those for starved fry.
    • Book

      Sea bass hatchery operations. 

      MM Parazo, LMB Garcia, FG Ayson, AC Fermin, JME Almendras, DM Reyes Jr., EM Avila & JD Toledo - 1998 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Series: Aquaculture extension manual; No. 18
      The manual addresses sea bass (Lates calcarifer) fry production in the hatchery. It describes the principles and practical procedures for rearing sea bass - from eggs until metamorphosis - as practiced by the SEAFDEC Aquaculture Department in Tigbauan, Iloilo, Philippines. It is presented under the following main section headings: General principles; biology; Selecting a suitable site; Design - tank systems, seawater supply system, freshwater supply system, aeration system, other facilities; Broodstock - source of breeders, breeding techniques; Egg collection, transport and hatching; Larval rearing - stocking density, feed types and feeding management, water management size-grading of larvae; Harvest and transport of fry; and, Propagation of larval food - Chorella, Brachionus, Artemia, Moina.
    • Article

      Size- and weight-dependent cannibalism in hatchery-bred sea bass (Lates calcarifer Bloch) 

      MM Parazo, EM Avila & DM Reyes Jr. - Journal of Applied Ichthyology, 1991 - Blackwell Publishing
      The relationship of predator size to maximum prey size, and predator weight to weight of prey consumed among cannibalistic sea bass (Lates calcarifer Bloch) in a hatchery were assessed. Maximum prey size was computed from morphological measurements (predator mouth width, prey body depth and fish total length), while prey consumption was determined from predators kept in experimental beakers and fed only prey sea bass for a 7-day period. Maximum prey size was 61–67 % of predator total length (TLprey = 0.5944 TLpredator+ 0.0724). Gut dissection of predators showed that size of ingested prey increased with increasing predator size not exceeding the maximum size limit indicated by the above equation. Daily prey consumption of predators in the beakers was expressed as WPrey = -0.2407 Wpredator+ 0.7697Wpredator-0.1141. During hatchery rearing of sea bass, fish with length differences of more than 33 % must be separated and food of appropriate size provided to limit cannibalism.
    • Article

      Yolk and oil globule utilization and developmental morphology of the digestive tract epithelium in larval rabbitfish, Siganus guttatus (Bloch) 

      EM Avila & JV Juario - Aquaculture, 1987 - Elsevier
      The purpose of this study was to find out how yolk and oil globule absorption in Siganus guttatus proceed as the digestive tract develops, in order to determine the probable causes of early larval mortality. Yolk and oil globule absorption in the rabbitfish were compared with the same processes in the more sturdy seaperch larvae during the first 10 days of larval life under identical rearing conditions in 32‰ sea water at 27°–30°C. The rapid decline of yolk in both species coincided with the rapid development of the digestive system within 24 h from hatching, indicating that most of the yolk was used for organogenesis. Whereas yolk was depleted in both fish in 3 days, the oil globule persisted in the rabbitfish only for 4 days and in the seaperch for 7 days. Oil globule depletion in the rabbitfish coincided with a negative mean length increment, implying an energy deficit even when the larvae had already started to feed. Ultrastructural observations of the gut epithelia of the rabbitfish revealed pinocytosis in the hindgut cells immediately after ingestion of rotifers, well in advance of complete yolk and oil globule absorption. Therefore, starvation due to exhaustion of the endogenous energy reserves in addition to the physical inability to feed were ruled out as major causes of larval mortality in rabbitfish.