To assist the reproductive management of tambaqui (Colossoma macropomum) males in laboratory and commercial fish farming, a linear regression model was obtained from concentration curves using the spectrophotometric method. Twenty-two tambaqui males with an average age of three years old were selected and divided into two groups containing 11 animals each. Both groups alternately received a single dose of carp pituitary extract (CPE; 2.0 mg/kg body weight, intracoelomic). Sperm was collected 14 h after hormonal treatment and diluted (1:4000; sperm:formaldehyde saline). The concentration was estimated by counting spermatozoa in a Neubauer chamber and by using a spectrophotometer (λ=540 nm). Individual sperm concentration ranged from 11.40 to 71.13 × 109 sperm/mL. The degree of transmittance ranged from 62.1% to 95.0%. There was a significant correlation (r2 = 0.966; p < 0.0001) between sperm concentration analyzed in a Neubauer chamber and transmittance at 540 nm. Analysis by spectrophotometry and the prediction provided by the equation Y=100.293 - 0.509X proved to be an efficient and fast method for estimating sperm concentration in tambaqui and can be used in routine procedures in artificial fish reproduction laboratories.

Resumo Visando auxiliar o manejo reprodutivo de machos de tambaqui (Colossoma macropomum) em piscicultura de laboratório e comercial, obteve-se um modelo de regressão linear a partir de curvas de concentração por método espectrofotométrico. Foram selecionados 22 machos de tambaqui com idade média de três anos. Eles foram divididos em dois grupos contendo 11 animais cada. Ambos os grupos receberam alternadamente uma única dose de extrato de hipófise de carpa (EHC; 2,0 mg/kg de peso corporal, intracelomático). O esperma foi coletado 14 horas após o tratamento hormonal e diluído (1:4000; esperma: solução salina formaldeído). A concentração foi estimada por contagem de espermatozoides em câmara de Neubauer e por espectrofotômetro (λ=540 nm). A concentração espermática individual variou de 11,40 a 71,13 × 109 espermatozoides/mL. O grau de transmitância variou de 62,1 a 95,0%. Houve correlação significativa (r2 = 0,966; p < 0,0001) entre a concentração espermática analisada em câmara de Neubauer e a transmitância em 540 nm. A análise por espectrofotometria e a predição pela equação Y=100,293 - 0,509X mostrou ser um método eficiente e rápido para estimar a concentração espermática de tambaqui, podendo ser utilizado em procedimentos de rotina em laboratórios de reprodução artificial de peixes.

The present study aimed at determining the effects of dietary DL-methionine supplementation on the water quality, bioflocs composition and Nile tilapia juvenile’s (initial body weight = 2.76 ± 0.06 g) growth performance in BFT rearing tanks (18 fish/100-L tank). Fish were or not subjected to artificial feed restriction. The experimental treatments consisted of two control groups: 1 - no feed restriction, no methionine supplementation; 2 - feed restriction at 25%, no methionine supplementation. There were also four treated groups: 1 - feed restriction at 25%, dietary DL-methionine supplementation at 0.5%; 2 - feed restriction at 25%, dietary DL-methionine supplementation at 1.0%; 3 - feed restriction at 25%, dietary DL-methionine supplementation at 2.0%; 4 - feed restriction at 25%, DL-methionine supplementation of molasses at 1.0. Supplementation of the commercial diet with DL-methionine has not affected either the water quality of the BFT Nile tilapia rearing tanks or the proximate composition of the bioflocs. After 8 weeks, weight gain of fish reared in tanks with feed restriction and dietary DL-methionine supplementation at 1% or 2% has not differed (P>0.05) from the tanks without feed restriction. In conclusion, it is possible to restrict the daily feed allowances of Nile tilapia juveniles reared in BFT tanks at 25%, with no growth performance impairment, if a minimal dietary DL-methionine supplementation of 1.0% is given.

RESUMOLocalizado a 48 km da cidade de Fortaleza, o distrito de Iguape possui uma pequena praia frequentada por moradores da região, sendo reduto de pescadores que trabalham de forma artesanal e tiram da pesca o seu sustento. Visto a importância que essa atividade econômica tem para a população local, o objetivo desta pesquisa foi caracterizar a pesca artesanal, analisar a biodiversidade da ictiofauna e saber quais aquelas que são de importância econômica para a comunidade. Os resultados mostraram que são utilizadas embarcações do tipo jangadas e paquetes a vela e botes a remo em pescarias de "ir e vir" e de "dormir". As pescarias são realizadas com linha de mão, tarrafas e redes de espera. Foram capturados 2.655 espécimens, inseridos em duas classes, sete ordens, 18 famílias e 32 espécies, revelando uma elevada diversidade e riqueza de espécies, com destaque para Harengula clupeola, Opisthonema oglinum, Haemulon parra e Haemulon plumierii, que contribuem acentuadamente para a renda da comunidade pesqueira.Palavras-chave: atividade econômica, peixe marinho, embarcações. ABSTRACTLocated at 48 km from Fortaleza, the district of Iguape has a small beach frequented by residents of the region, it is a redoubt of artisanal fishermen that have the fishing as the main income. Considering the importance of this economic activity to the local population, the objective of this research was to characterize the artisanal fishery, to analyze the biodiversity of the fish fauna and to know which ones are of economic importance to the community. The fleet is composed by small wooden rafts that are hollow or filled with Styrofoam and driven by sail or paddle. The fishing activities last from some hours to 2 days. The fisheries are carried out with handlines, casting nets and gillnets. A total of 2.655 specimens were caught, belonging to 2 classes, 7 orders, 18 families and 32 species, revealing a high diversity and species richness, mainly from Harengula clupeola, Opisthonema oglinum, Haemulon parra and Haemulon plumieri, contributing significantly to the fishing community income.

Aiming at analyzing the water quality at Iracema Beach, in Fortaleza/CE, as well as characterizing the planktonic community, monthly collections were carried out between February and November 2019, with 100 liters of water being filtered, concentrated to 10 mL and preserved in 4% formalin. In the laboratory, via microscopy, the plankton species were identified and then classified based on references relevant to the subject, as well as consultations with specialists and electronic addresses. Furthermore, data on water temperature, transparency, salinity, dissolved oxygen and pH were obtained in situ. Bimonthly, one liter of water was collected for microbiological analysis, in the laboratory. The parameters analyzed showed good quality water, with 17 phytoplankton species being recorded, distributed among the Classes Cyanophyceae, Bacillariophyceae, Euglenophyceae, Chlorophyceae, Mediophyceae, Coscinodiscophyceae and Zygnematophyceae. For zooplankton, there were five species included in the Rotifera, Cladocera and Crustacea Classes. Phytoplanktonic species diversity was high, the zooplanktonic was low; very high equability and low species richness in both communities. No species was considered a bioindicator of eutrophication or pollution, and the microbiological analysis showed minimum values ​​of thermotolerant coliforms, and the waters of Iracema Beach can be classified as class one saline, intended for recreation and with a very good quality.

The work aimed at determining the effects of applying different blends between liquid molasses and agricultural limestone on water quality and growth performance of Nile tilapia juveniles, Oreochromis niloticus. The study employed 24 indoor tanks of 100 L and 24 outdoor tanks of 250 L. Four control groups were set up (no product applied, only molasses, only limestone, molasses-limestone blend with 48% limestone but no fish) and two experimental groups (molasses-limestone blends with 32% and 48% molasses), with four replicates each. Over 11 weeks, the water quality was monitored systematically. The 24-h cycle monitoring of temperature, pH, specific conductance, dissolved O2 and total alkalinity were carried out at the 8th week. The blends between molasses and limestone accelerated the dissolution rate of the agricultural limestone in water. The blend containing 48% molasses led to greater increases in water alkalinity and pH in relation to tanks with only limestone applications. However, the molasses-limestone blend applications impaired the Nile tilapia growth performance, especially in the outdoor tanks. While the fish yield was 25.1 g m-3 day-1 in the molasses outdoor tanks, it was equal to 22.8 g m-3 day-1 in the molasses (32%)-limestone units (P<0.05). It has been concluded that the blending between limestone and molasses brings no clear benefits to Nile tilapia’s rearing tanks when compared to the limestone-only tanks.

No abstract

The present work aimed at assessing the possibility of compensating the notorious deficiencies of bioflocs in lipids by supplementing the tilapia commercial diet with soybean oil. In the positive control, there was no feeding restriction nor dietary supplementation with soybean oil. In the experimental treatments, the commercial diet was restricted by 25% over the positive control level. In the negative control tanks, there was feeding restriction and the artificial diet had no oil supplementation. In the experimental tanks, soybean oil was mixed daily with the commercial diet at the levels of 0.6%, 1.2 and 2.4%. Additionally, there were fed-restricted tanks that received a daily supplementation of 1.2% soybean oil mixed with dry molasses, and not with the commercial diet. In general, only the restriction of the commercial diet affected the water quality. The supplementation of the artificial diet with soybean oil up to 2.4% has not improved the proximate composition of bioflocs, nor the fish growth performance. It was concluded that the strategy of supplementing the Nile tilapia juveniles’ commercial diet with increasing levels of soybean meal, in BFT tanks submitted to 25%-feeding restriction, was not capable of avoiding the fish growth performance deterioration.