UPV Digital RepositoryUPV-DRUniversity of the Philippines Visayas
 

UPV Theses and Dissertations

Permanent URI for this communityhttps://hdl.handle.net/20.500.14583/10

Browse

Filters

2015 - 20172

Settings

AGROVOC Keyword: search.filters.agrovoc.stressKeyword: search.filters.keyword.mortality

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Influence of cooling of crab (Scylla spp.) juveniles on the physiological changes and survival during storage
    Geromiano, Merlyn F. (University of the Philippines Visayas, 2017-06)
    Considering that aquaculture of mud crabs is still dependent on wild seeds, mortalities associated with capture, handling and storage aggravates the problem of lack of seeds which is one of the major constraints affecting the development of the mud crab aquaculture industry. Having cold rooms for maintaining optimum environment for storage has been recommended, however these facilities are not available in all levels of the industry and can only be found in some of the major traders. To address this issue, this study tested a handling and storage scheme that can be used at various points along the harvest to market chain. In lieu of cooling crabs in a chamber, crabs were directly immersed in seawater of different temperatures (4°C, 7°C, 15°C and 29°C) and stored for 48h, 72h and 96h. Crabs that were cooled at 15°C for 3 min showed highest survival (88-90%) after 48h, 72h and 96h of storage. In addition, the least accumulation of glucose and lactic acid in the haemolymph was detected in crabs cooled at 15°C regardless of the storage period, which suggests that crabs were fess stressed when cooled at this temperature.
  • No Thumbnail Available
    Item
    Assessment of induced stress as schemes for selectively removing fish with opercular deformities in hatchery produced milkfish (Chanos chanos) seeds
    Cordero, Christian P. (College of Fisheries and Ocean Sciences, University of the Philippines Visayas, 2015-06)
    The effects of different types of induced stress were tested as schemes for the elimination of fish with opercular deformities in hatchery produced milkfish seeds. Salinity and pH were used as the main stressors for milkfish larvae of different ages. Induced salinity stress was initially tested on larvae at 15 days post-hatch (dph) by directly transferring the larvae from its rearing water salinity of 32 ppt to salinities of 10 ppt, 25 ppt, 35 ppt and 45 ppt. Almost all of the larvae subjected to salinity stress dies, hence, it was deemed necessary to examine the influence of handling stress and to determine the age of larvae that could tolerate handling. Larvae of different ages (from 10 dph to 22 dph) were thus subjected to handling stress by collecting them from the mass rearing tank and transferring them to 1000 ml beakers where survival was monitored. Results showed that milkfish larvae were able to withstand handling stress beginning 21 dph. Considering that milkfish fry (21 dph) are already known to tolerate direct transfers to various salinities, the next experiments were focused on pH stress. The suitability reduced or increased pH as stressors were initially tested by directly transferring larvae from normal seawater (pH 7.50) to acidic water (pH 6.5-7.0) and basic seawater (pH 8.0-8.5). Results revealed several advantages of reducing pH levels over increasing pH levels, which included the comparably higher larval survival, the lesser amount of chemicals required to change pH levels and the corresponding cost of these chemicals. A range finding test was then conducted to determine the optimum pH that could selectively remove fry with opercular deformities by directly transferring fry reared in normal seawater (pH 7.50) to seawater with reduced pH: Trt 1-pH 6.5; Trt 2-pH 6.6; Trt 3-pH 6.7; and Trt 4-6.8. Larval mortalities were recorded after 1 h, then 25% water change was done for all treatments which were monitored further for mortalities after 2h, 3h, 5h, and 24h. The surviving larvae from all the treatments were reared further for 18 days (until 40 dph) in order to monitor opercular deformities which can observed only when the larvae have metamorphosed into juveniles. Results showed that a sudden drop in pH of normal seawater to pH 6.5-6.7 selectively removed all the fish with opercular deformities in hatchery produced milkfish seeds; at such pH range, more than 90% survival of milkfish fry was obtained with this batch of larvae and all the surviving fish had no opercular deformities.