Anaesthetic efficacy of eugenol was investigated on iridescent shark, Pangasius hypophthalmus. Fish (2, 5, 10 and 20 g) subjected to 20–200 mg L−1 eugenol and behavioural response as well as induction and recovery times were recorded. Induction and recovery times were significantly affected by eugenol concentration as well as fish weight (P < 0.05). Generally, 27–300 s after exposure to 20–200 mg L−1 eugenol, iridescent sharks reached stage 3 anaesthesia (suitable for general handling). Fish entered stage 4 anaesthesia (suitable for surgery and blood sampling) over 54–710 s exposure to such concentrations. Recovery time was 109–600 s in all weight classes as well as eugenol concentrations. Mortality (44–100%) was only observed in 2 g fish when subjected to 110–170 mg L−1 eugenol. This study, for the first time, showed behavioural response of iridescent shark to anaesthesia as well as effectiveness of eugenol as anaesthetic in this important aquaculture‐ornamental species. According to the models obtained in this study, minimum eugenol concentrations to induce anaesthesia over less than 3 min were 53.8–81.5 mg L−1 in 2–20 g fish. Likewise, maximum eugenol concentrations in which fish recovered over less than 5 min were 65.9–105.8 mg L−1 in 2–20 g fish.

Anaesthetic efficacy of eugenol was investigated on Flowerhorn (Amphilophus labiatus 9 Amphilophus trimaculatus). A total of 104 fish with average weights of 12 AE 2.5, 28 AE 5 and 53 AE 5.1 g were subjected to 25-200 mg L À1 eugenol and behavioural responses as well as induction and recovery times were recorded. Induction and recovery times were significantly affected by eugenol concentration as well as fish weight (P < 0.05). Generally, 49.9-127.3 s after exposure to 50-200 mg L À1 eugenol, fish reached stage 3 anaesthesia (suitable for general handling). Fish entered stage 4 anaesthesia (suitable for surgery and blood sampling) over 57.3-140.4 s post exposure to such concentrations. Recovery time was 91.7-312 s in all weight classes for all eugenol concentrations. Mortality (23%) was only observed in 12-g fish when were subjected to 200 mg L À1 eugenol. This study showed the behavioural response of Flowerhorn to anaesthesia and eugenol efficacy as an anaesthetic in this important ornamental species. The general quadratic equation revealed that concentrations of eugenol and fish size along with their interactive effects have significantly contributed to the model, with concentration recording the highest beta value in all models (b = À0.809, À0.818 and À0.909, P = 0.000). According to the results, minimum eugenol concentration to induce anaesthesia in less than 3 min was 50 mg L À1 .

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The effect of two insecticides, diazinon and deltamethrin, was investigated on hematological parameters and gill morphology in iridescent shark, Pangasius hypophthalmus. Fish were exposed to 0.5 and 1 ppm diazinon as well as 0.015 and 0.020 ppm deltamethrin over a 7-day period. Both insecticides caused leukocytosis, lymphopenia, neutrophilia as well as increases in red blood cell (RBC), hematocrit (Ht), hemoglobin (Hb) and mean corpuscular volume (MCV). Morphological gill damages were observed in fish exposed to both pesticides. It is suggested that diazinon and deltamethrin changed immune function and induced gill damages which could be the reason of increase in RBC, Ht, Hb and MCV in iridescent shark.

Potassium permanganate (PM) is a therapeutic agent in aquaculture with strong oxidant properties. In this study, the effects of potassium permanganate treatment (PMT) on stress response and blood biochemistry were investigated in goldfish Carassius auratus. Two triplicate groups of fish were exposed to either 10 mg L À1 PM or clean water, over 30 min. Blood samples were collected at 0 and 0.5 h after exposure as well as 3 and 24 h. PMT caused significant increase in serum cortisol and glucose levels, 0.5 h post exposure, which stayed elevated until 24 h. Sodium decreased after exposure and did not return to initial levels. Chloride decreased at 0.5 and 3 h, but returned to initial levels at 24 h. Calcium decreased at 0.5 h and returned to initial at 3 h, but significantly increased at 24 h. Total protein, albumin and globulin levels increased at 3 h and stayed elevated until 24 h. Albumin:globulin ratio (A:G) levels decreased at 24 h post exposure. Results indicated that short-term PMT caused stress response, hydromineral imbalance and possibly change in blood protein profile in goldfish, which lasted until 24 h post treatment.

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Anaesthetic efficacy of eugenol was investigated on Pterophyllum scalare. A total of 130 fish with average weights of 1.0 ± 0.5, 5.0 ± 1.0 and 10.0 ± 1.0 g were subjected to 1.25, 2.5, 4.0, 5.5 and 7.0 mg/L eugenol, and behavioural responses were observed. Induction and recovery times were significantly affected by the interactive effect of eugenol concentration and fish weight (p < .05). Generally, 49.9–128 s after exposure to 1.25–7 mg/L eugenol, fish reached stage 3. Fish entered stage 4 over 55–135 s post exposure to such concentrations. Recovery time was 393.5–597.7 s in all sizes. Any increase in eugenol concentration led to a significant decrease in the induction time with a subsequent increment of the recovery time. Concentrations of eugenol and fish size along with their interactive effects have significantly contributed to the regression models, with concentration recording the highest beta values for stages 1, 2, 3 and 4 (−0.903, −0.898, −0.976 and −0.864 respectively) and the product of size and anaesthetic concentration for full recovery in smaller fish (0.647) and eugenol concentration in larger ones (0.967). Recovery time was fitted to induction time to stage 4 via quadratic and linear regression models in smaller and larger fish respectively. Results revealed the minimal eugenol concentration to induce anaesthesia in various size classes of angelfish in less than 3 min was 1.25 mg/L. Our results showed eugenol as an effective and safe anaesthetic; however, it is not advisable for live fish transportation.

Background:The expansion of herbicide used in aquatic ecosystems as well as in terrestrial if is