Selective fishing is the successful capture of target species and size classes in a way that minimises bycatch, minimises damage to flesh, and maximises post-mortem (PM) value. We studied selective harvesting of blue cod Parapercis colias (Pinguipedidae) in central New Zealand, where it is captured mainly by commercial pot-fishing and recreational line-fishing. Potting with paua Haliotis iris (=abalone) guts selectively targeted large blue cod from localities that had six or more fish species and many small blue cod. Video observations of pot entries indicated that blue cod entered and left the pot throughout 30 min sets. Blue cod were observed by video to commence swimming when pot-hauling started. Observations of line-hooked fish indicated a characteristic spinning behaviour while hauling.
Fatigue during harvesting is a major factor in reducing the PM quality and shelf-life of fish muscle. Despite the relatively benign nature of capture via pot, it appears that burst exercise during hauling and a brief flurry of flapping as the pot leaves the water is sufficient to compromise flesh quality. Fish that were fatigued during harvesting had a poorer peri-mortem ‘ATP potential’ than fish that had been tank-rested for a year and then harvested using rested harvesting techniques. Modifying the potting method by providing a reservoir of water reduced peri-mortem fatigue during capture but by an insufficient amount to significantly improve PM flesh quality.
Blue cod flesh is compromised by pot capture, which is widely perceived as a benign harvesting method. In order to maximise value of blue cod, low-stress harvesting methods which take advantage of the behaviour of the fish are required. 相似文献
Musculoskeletal injuries are a common cause of lost training days and wastage in racehorses. Many bone injuries are a consequence of repeated high loading during fast work, resulting in chronic damage accumulation and material fatigue of bone. The highest joint loads occur in the fetlock, which is also the most common site of subchondral bone injury in racehorses. Microcracks in the subchondral bone at sites where intra‐articular fractures and palmar osteochondral disease occur are similar to the fatigue damage detected experimentally after repeated loading of bone. Fatigue is a process that has undergone much study in material science in order to avoid catastrophic failure of engineering structures. The term ‘fatigue life’ refers to the numbers of cycles of loading that can be sustained before failure occurs. Fatigue life decreases exponentially with increasing load. This is important in horses as loads within the limb increase with increasing speed. Bone adapts to increased loading by modelling to maintain the strains within the bone at a safe level. Bone also repairs fatigued matrix through remodelling. Fatigue injuries develop when microdamage accumulates faster than remodelling can repair. Remodelling of the equine metacarpus is reduced during race training and accelerated during rest periods. The first phase of remodelling is bone resorption, which weakens the bone through increased porosity. A bone that is porous following a rest period may fail earlier than a fully adapted bone. Maximising bone adaptation is an important part of training young racehorses. However, even well‐adapted bones accumulate microdamage and require ongoing remodelling. If remodelling inhibition at the extremes of training is unavoidable then the duration of exposure to high‐speed work needs to be limited and appropriate rest periods instituted. Further research is warranted to elucidate the effect of fast‐speed work and rest on bone damage accumulation and repair. 相似文献