Abstract Among the different handling techniques in aquaculture, the use of anesthetics has had a growing interest focused on guaranteeing animal welfare, and reducing possible stress situations during general handling. The aim of this study was to present the use of eugenol and lidocaine with non-invasive anesthesia procedures in Dormitator latifrons, in which the different stages of anesthesia (induction and recovery) were determined. One hundred and twenty healthy fish of average weight of 73.59 ± 13.53 g and standard length of 17 ± 1.36 cm were used. The experimental fish were subjected to fasting for 24 h prior to the tests. Five fish were subjected to eugenol (25, 50, 100, and 200 µL/L), and lidocaine (100, 200, 300, and 400 mg/L), in triplicate. The time to reach deep and recovery anesthesia were recorded and the data analyzed using ANOVA (α= 0.05). Organisms exposed to anesthetics evidenced early episodes of fast, short-distance swimming (initial hyperactivity) for short periods of time. Survival was 100% with both compounds and concentrations. Fish exposed to a eugenol concentration of 200 µL/L had longer anesthesia times and took longer time to recover (P<0.05). The most effective concentrations for eugenol and lidocaine were of 200 µL/L and 400 µL/L in juvenile fish, promoting rapid inductions, without compromising the conditions for the recovery of the fish. This work provides practical information for handling and transportation D. latiforns with the least possible stress and ensuring animal welfare.

Resumo Dentre as diferentes técnicas de manejo na aquicultura, o uso de anestésicos tem despertado interesse crescente voltado para a garantia do bem-estar animal, reduzindo possíveis situações de estresse durante o manejo geral. O objetivo deste estudo foi apresentar o uso de eugenol e lidocaína com procedimentos anestésicos não invasivos em Dormitator latifrons, nos quais foram determinadas as diferentes etapas da anestesia (indução e recuperação). Foram utilizados 120 peixes saudáveis, com peso médio de 73,59 ± 13,53 g e 17 ± 1,36 cm de comprimento, em jejum de 24 horas antes dos testes. Cinco peixes foram submetidos a eugenol (25, 50, 100 e 200 µL/L) e lidocaína (100, 200, 300 e 400 mg/L), em triplicata. O tempo para atingir a anestesia profunda e de recuperação foi registrado, os dados foram analisados com ANOVA (α= 0,05). Organismos expostos a anestésicos evidenciaram episódios precoces de nado rápido de curta distância (hiperatividade inicial) por curtos períodos de tempo. A sobrevivência atinge 100% com ambos compostos e concentrações. Peixes expostos a uma concentração de eugenol de 200 µL/L tiveram tempos de anestesia mais longos e demoraram mais para se recuperar (P<0,05). As concentrações mais efetivas para eugenol e lidocaína foram de 200 µL/L e 400 µL/L em peixes juvenis, promovendo induções rápidas, sem comprometer as condições de recuperação dos peixes. Este trabalho fornece informações práticas para o manejo e transporte de D. latifrons com o mínimo de estresse possível e garantindo o bem-estar animal.

Abstract A little-studied characteristic of the Mexican native fish Dormitator latifrons is the effect that the color of the bottom or lining of ponds or tubs can have on their growth and blood parameters under controlled conditions. After a quarantine period in prophylactic treatment, an initial assay was performed. The organisms were grouped into four treatments (white, yellow, blue, and black) in triplicate, with 30 individuals with an average weight of 34.7± 2.5 g and average size of 12.5 ± 1.5 cm per tank. The trial lasted 60 days, after which a final biometry to all specimens and blood extractions to six random organisms per tank were performed. The following hematological and blood chemistry parameters were evaluated: erythrocytes, cell counts, and differential counts, as well as glucose, albumin, a/g ratio, and total proteins. Final weight, weight gain, and specific growth rate presented statistical differences between treatments (p<0.05), with dark bottoms (blue and black) above 80% of WG and above 1.0 of SGR. No statistically differences were found in hematological blood chemistry parameters (p>0.05). The growth results suggest that dark pond bottoms promote the adaptation of Dormitator latifrons by allowing it to avoid detection by predators through the adoption of a cryptic coloration. However, the species shows a great capacity for crypsis, being able to change its pigmentation to adapt to different bottom colors.

Resumo Uma característica pouco analisada do peixe nativo Dormitator latifrons é o efeito que a cor do fundo ou revestimento de tanque, ou banheiras pode ter sobre seu crescimento e parâmetros sanguíneos em condições controladas. Após um período de quarentena em tratamento profilático, foi realizado um bioensaio inicial. Os organismos foram agrupados em 4 tratamentos (branco, amarelo, azul e preto) em triplicata, com 30 indivíduos por viveiro. O bioensaio durou 60 dias, após os quais foi realizada uma biometria final e extrações de sangue. Os seguintes parâmetros hematológicos e bioquímicos foram avaliados: eritrócitos, contagem de células, contagens de diferenciais, glicose, albumina, relação a/g, e proteínas totais. O peso final, o ganho de peso e a taxa de crescimento específico apresentaram diferenças entre os tratamentos, em fundos escuros (azul e preto), os parâmetros citados foram maiores. Não foram encontradas diferenças estatisticamente significativas nos parâmetros químicos hematológicos do sangue. Os resultados sugerem que os fundos escuros dos tanques promovem a adaptação e o crescimento dos Dormitator latifrons, permitindo que eles evitem a detecção por predadores através da adoção de uma coloração críptica. No entanto, a espécie apresenta grande capacidade de cripse, podendo alterar sua pigmentação para se adaptar a diferentes cores de fundo.

Total replacement of cod liver oil by vegetable oils in the diets of juvenile California halibut (Paralichthys californicus) was analyzed. Five diets were formulated with olive oil, corn oil, linseed oil, and two combinations of linseed oil and corn oil, and compared with a control diet containing cod liver oil during a 12-week feeding experiment. Highest growth was observed in fish fed the control diet; however, no significant differences in growth and survival were observed among the dietary treatments. The fatty acids from linseed, corn, and olive oils were the most accumulated in the tissue, increasing in proportion to the total fatty acids. Reduced levels of 20:5n-3 and 20:4n-6 in the presence of high dietary levels of 18:3n-3 and 18:2n-6 suggest that, as in most marine fishes, synthesis of 18:3n-3 to 20:5n-3 and of 18:2n-6 to 20:4n-6 is either very limited or does not occur. Although the content of 22:6n-3 in the muscle of fish fed the control diet was approximately 2.0 to 2.5 times greater than that in the muscle tissue of fish fed the experimental diets, no significant differences were detected. A proportional decrease in 20:5n-3 among all fatty acids and a lack of an increase in body tissue suggest that this fatty acid was being used to synthesize 22:6n-3. The significant reductions in the level of 20:5n-3 indicate that if the experiment had been conducted over a longer period of time, a level would eventually be reached whereby the dietary deficiency would presumably be reflected by an adverse effect on growth. Additional research is needed, particularly regarding the proportional and quantitative changes of 20:5n-3 and 22:6n-3 in the composition of the muscle tissue.

Se estudió el reemplazo total de aceite de hígado de bacalao por aceites vegetales en las dietas de juveniles de lenguado de California (Paralichthys californicus). Se formularon cinco dietas con aceites de oliva, maíz, linaza y dos combinaciones de linaza y maíz, y se compararon con una dieta testigo que contenía aceite de hígado de bacalao. Después de 12 semanas de experimentación se observó un crecimiento mayor en los ejemplares alimentados con la dieta testigo; sin embargo, no hubo diferencias significativas en crecimiento y supervivencia entre las dietas experimentales. Los ácidos grasos provenientes de los aceites de linaza, maíz y oliva fueron los más acumulados en los tejidos, incrementando en proporción al total de ácidos grasos. Una reducción de 20:5n-3 y 20:4n-6 en presencia de altos niveles dietéticos de 18:3n-3 y 18:2n-6 sugiere que, como en la mayoría de los peces, la síntesis de 18:3n-3 a 20:5n-3 y de 18:2n-6 a 20:4n-6 es muy baja o inexistente. Aun cuando el contenido de 22:6n-3 en el músculo de los ejemplares alimentados con la dieta testigo fue aproximadamente de 2.0 a 2.5 veces más alto que en el de los ejemplares alimentados con las dietas experimentales, no se observaron diferencias significativas. Un decremento proporcional de 20:5n-3 en comparación con todos los ácidos grasos y la ausencia de un incremento en el tejido sugiere que este ácido graso se utilizó en la síntesis de 22:6n-3. Las reducciones significativas en el nivel de 20:5n-3 indican que si se hubiera realizado el experimento durante un periodo de tiempo más largo, se hubiera llegado a un nivel en donde se registrarían efectos adversos en el crecimiento. Es necesario realizar más estudios, especialmente sobre los cambios proporcionales y cuantitativos de 20:5n-3 y 22:6n-3 en la composición del tejido muscular.