Stress during fish culture can impact growth, physiology and fillet quality. Maintenance of high quality seafood is important to ensure the production of a highly marketable product. The present study assessed how sequential stressors affect the physical, physiological, sensory and quality characteristics of channel catfish (Ictalurus punctatus) fillets. Temperature (25°C or 33°C) and dissolved oxygen (DO, ~2 mg/L or >5 mg/L) were maintained for four weeks, followed by socking and transport stress for a total of 12 treatments. After each stage of stress (environment, socking and transport), physical (length, weight and feed consumption), physiological (hematocrit, plasma cortisol, pH, glucose, lactate, total protein, osmolality and ionic composition) and fillet quality (color, texture, sensory and pathogen load) attributes of the fish and fillets were evaluated. Fillet yield decreased with increasing severity of environmental stress. Overall, increasing stress resulted in decreased feed consumption, growth and fillet yields. A cumulative stress response was identified with regard to circulating cortisol and glucose, which increased with each sequential stress event. Under low oxygen conditions there was a suppression of the stress response. Handling imposed a more pronounced physiological response than environmental conditions. The sequential stressors resulted in a less intensely colored fillet that was less red, which suggests the quality changes imposed are beneficial to the marketability of the fillets. However, increased redness in fish reared under high temperatures and oxygen levels suggest that an increased prevalence of red fillets can be expected. Sensory analysis revealed that fillet flavor was acceptable in all treatments with the severe stress treatment preferred due to lower intensity of less favorable flavor attributes. The changes in flavor were presumably due to fasting of the stressed fish and a subsequent purging of fat stores. As fish progressed through the harvest event, cook loss decreased, tenderness increased and pH increased, indicating that stress induced positive textural changes. Proteomic analysis revealed mainly down-regulation of structural and metabolic proteins, which indicates higher proteolytic activity and an adjustment in energy metabolism in response to stress. The overall effects of chronic environmental conditions and handling highlight the importance of managing for stress in cultured channel catfish.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-5442 |
| Date | 11 December 2015 |
| Creators | Ciaramella, Mike |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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