Impact of transport conditions and underlying disease on post-stocking survival of juvenile Lates calcarifer
Chew, Xian Zhe, Carrai, Maura, Shen, Xueyan, and Gibson-Kueh, Susan (2024) Impact of transport conditions and underlying disease on post-stocking survival of juvenile Lates calcarifer. Journal of Fish Diseases, 47 (8). e13963.
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Abstract
Diseases caused by pathogens commonly occurring in the aquatic environment or those that are non-host specific are prevalent and threaten the rapid growth of tropical aquaculture. This study investigates causes of mortality in 12 batches of newly stocked juvenile Lates calcarifer from three different hatcheries. Cytology based on Diff-Quik™-stained tissue and blood smears provides rapid diagnosis of possible causes of mortality, while histopathology and haematology provide a better understanding of how prolonged transport and fish with existing chronic disease are more likely to experience elevated mortality post-stocking. Our findings showed that accumulation of ammonia during prolonged transport causes extensive damage to epithelial barriers in gastrointestinal tracts and depressed immunity due to marked hypoglycaemia, predisposing fish to acute Streptococcosis. Lates calcarifer with chronic bacterial enteritis developed severe hypoglycaemia, had low circulating total plasma protein, and suffered high mortality within 24 hours post-stocking. Hypoglycaemia and low circulating blood proteins disrupt osmoregulation and exacerbate dehydration, which is fatal in fish in sea water. Dying L. calcarifer tested PCR positive for scale drop disease virus (SDDV) at 28 days post-stocking showed a 10-fold elevation of white blood cell counts, severe vasculitis, and obstruction of blood supply to major organs. Destruction of important immune organs such as spleen is a hallmark of SDDV infection that explains high incidences of opportunistic Vibrio harveyi infections in 61% of fish with SDDV. Overall, this study reiterates the importance of stocking disease-free fish and reducing transport stress.
| Item ID: | 83396 |
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| Item Type: | Article (Research - C1) |
| ISSN: | 1365-2761 |
| Keywords: | ammonia, aquaculture, cytology, haematology, histopathology, transport stress |
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| Copyright Information: | This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2024 The Authors. Journal of Fish Diseases published by John Wiley & Sons Ltd. |
| Additional Information: | Codes added WB 09.08.24 |
| Date Deposited: | 09 Aug 2024 00:36 |
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