Customers expect perch, whether whole or processed, to be free of defects. The target defects level for perch products are zero.
Where whole fish have major defects they should be further processed if the resultant product complies with below. A number of typical defects are described below to help in their identification.
Whole fish – live and fresh chilled
Condition of live fish:
Silver perch destined for the live market must be in peak condition. Moribund perch exhibiting extreme signs of distress, such as reddening of the gills and disorientation during swimming, or lack of vigour should be excluded.
Spinal and mouth deformity:
Spinal and mouth deformity generally results from genetic and nutritional effects. Genetic deformities in grow-out perch can be minimised through improved grading processes prior to stocking in the grow-out pond.
Processes to improve the management of broodstock and scrutiny of fingerlings from supplying hatcheries may be appropriate. Similarly spinal deformity can occur through nutritional deficiencies such as vitamin C. Where high occurrences of deformities are noted samples should be forwarded to your local veterinarian for assessment.
The tolerance for perch with spinal and mouth deformity for live or whole fresh chilled perch is nil. Fish should be processed for the fillet market.
Fin rot:
Fin rot in perch is generally related to stressful handling and/or severe water quality stress during harvesting. With mild cases can be treatment in a salt bath of 5 ppt will assist the fish in fighting the infection. Severe cases should be quarantined where possible and a veterinarian called to prescribe registered chemicals.
The tolerance for perch with fin rot for live or whole fresh chilled is:
- Minor cases: 5%
- Major cases: nil - Fish should be processed for the fillet market.
Fin damage/Scale loss
Fin damage and scale loss in perch generally occur during harvesting and grading and can be minimised through improved harvesting and grading processes.
The tolerance for perch with fin damage and scale loss for live or whole fresh chilled perch is:
- Minor cases: 5%
- Major cases: nil - Fish should be processed for the fillet market.
Skin disease:
Skin disease of perch may include lesions, ulcerations, haemorrhage under the skin, and skin and muscle erosion. Instances of skin disease may infer a greater problem in the pond and cases should be quarantined and where possible and a veterinarian called to provide diagnosis and treatment.
The tolerance for perch with diseases for live or whole fresh chilled perch is nil. These fish should not be sold and instead discarded.
Use of chemicals:
Chemicals would not generally be used during the processing period, however if they are used they should be noted on the packaging. Only registered chemicals are to be used.
Processed fish – gilled & gutted and fillets:
Clean cavity for gilled & gutted perch
Following evisceration the body cavity should be cleaned and washed. The blood-line along the backbone should be removed. Tolerance for an unclean body cavity is nil.
Intact cavity wall for gilled & gutted perch:
The cavity wall should not be pierced, as a break in the cavity wall will cause a significant decrease in the shelf life of the perch. Tolerance for a pierced wall cavity is nil.
Pin bones for fillets:
Pin bones in fillets detract from the convenience factor and should be removed
Jagged fillets:
Each perch is cut to produce two fillets of uniform size, maximising the recovery rate, and with no jagged cuts. Tolerance for jagged fillets is 5%.
Use of chemicals:
Chemicals would not generally be used during the processing period, however if they are used they should be noted on the packaging. Only registered chemicals to be used.
Summary of tolerance levels for processed perch – gilled & gutted and fillets
Author:
Warwick Lee - Queensland Fisheries Service
Information Sourced From:
