Latin american journal of aquatic research vol. 51 num. 4 lang. en
- Geometric morphometric analysis of the variations in cephalothorax shape of the freshwater prawn Macrobrachium tenellum, Smith (Decapoda Palaemonidae) from two different coastal basins in Oaxaca, Mexicoel febrero 19, 2024 a las 4:59 pm
ABSTRACT Morphological variations of Macrobrachium tenellum prawns from two populations from locations in the Copalita and Colotepec riverine basins in the seashore of Oaxaca, Mexico, were studied with geometric morphometry techniques. The purpose was to find and explain significant differences in shape and size between the cephalothorax and the rostrum. Differences between sexes and populations were intended to prove intra and inter-populations. Results suggest low intrapopulation differences but significant interpopulation variation between specimens from different places, while a regression analysis suggests a higher correlation between shape and size only in males. The higher differences in places between and within sexes could be explained due to differences in environmental pressure. A positive allometry bias in males could indicate a sexual selection mechanism affecting mating.
- Impact of isolation on growth performance, behavior, and stress responses in Nile tilapia, Oreochromis niloticusel febrero 19, 2024 a las 4:59 pm
ABSTRACT The effects of isolation on the growth performance, behavior, blood hematology, and cortisol level of Nile tilapia, Oreochromis niloticus were checked in laboratory conditions. All fishes were closely observed for behavior and growth-related parameters. The weight and diameter of both the control and treatment groups were measured before and after the trial of 28 days using an electronic balance and measuring tape, respectively. At the end of the trial, blood was drawn from the caudal fin to determine some hematological and hormonal parameters. Significant differences were seen in growth performance, cortisol level, and hematology, as weight gain, specific growth rate, relative growth rate, and daily food intake were significantly higher in the control group. In comparison, cortisol levels and feed conversion ratio were significantly higher in the isolated group. White blood cells, lymphocytes, red blood cells, hemoglobin, hematocrit, and mean platelet volume, were significantly higher in the isolated group when compared to the control group. At the same time, the amount of granulocytes, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and platelets was significantly higher in the control group. Isolated fish showed aggressive behavior towards introduced fish from the control group. Isolation increased the cortisol level, which indicates that the fish was stressed. It is concluded that isolation significantly affects the growth performance, cortisol level, and hematology of O. niloticus.
- Sustaining local ecological knowledge of artisanal fishers: a perspective from northern Colombiael febrero 19, 2024 a las 4:59 pm
ABSTRACT Fishing is one of the oldest activities developed by humans for both food subsistence and economic gain. Artisanal fishing has a great social impact; it helps satisfy basic nutritional needs and generates income for communities. Therefore, local ecological knowledge associated with such fishing practices is important because of its capacity to provide data on fishing research. Fishing in the study area is largely artisanal for subsistence, a consequence of the fact that there are no fishing associations or cooperatives which might empower local workers and help promote the sector. We based our study on a quantitative approach. Through this approach, we analyzed factors that influence future fishing decisions among artisanal fishers in a community in northern Colombia. We found that socioeconomic conditions and pollution were important considerations when respondents contemplated future fishing prospects. Respondents’ perceptions of institutional support also influenced their attitudes about fishing. Most respondents planned to continue fishing. We encourage local authorities in such communities to address the challenges faced by artisanal fishers and develop strategies to improve the socioeconomic and environmental conditions in which such people work.
- Reproduction of Lutjanus guttatus (Perciformes: Lutjanidae) captured in the Mexican Central Pacificel febrero 19, 2024 a las 4:59 pm
ABSTRACT Research on the reproduction of snappers helps to manage and conserve them. The spotted rose snapper Lutjanus guttatus is a gonochoric species caught year-round in Navidad Bay, Jalisco, Mexico. This work aims to analyze the reproductive aspects of the spotted snapper L. guttatus caught in Navidad Bay on the southern coast of Jalisco, Mexico. Analyzed fish came from commercial catches. Organisms were sampled monthly from January 1998 to December 2008, and total length, total weight, sex, gonad weight, and gonadal phase were obtained for each specimen. Histological analysis was performed to define the gonadal phase and measure the oocytes' diameter. The total length range in the catches was 14.0 to 61.0 cm; 2889 females and 2792 males were collected for a sex ratio 1.0:0.97. The oocyte development is asynchronous, with a diameter range from 33.9 to 407.9 μm. The testicle is of the lobular type, with a well-defined spermatic duct. A main reproductive season from June to September was identified, although fish with mature gonads were observed in all months. The best condition was observed before the reproductive period. Average lengths at sexual maturity were 30.09 and 30.05 cm for females and males, respectively; the average length of capture in females (32.2 cm) and males (31.7 cm) corresponds to 66.6 and 64.6% of organisms that had reproduced at least once before being captured. Given the importance and continuous capture of L. guttatus in the study area, we recommend further studies to improve the understanding of reproductive and fishing activities.
- Contribution to some aspects of the digestive tract anatomy and food evacuation of the Pacific fat sleeper Dormitator latrifronsel febrero 19, 2024 a las 4:59 pm
ABSTRACT The development of feeding protocols and the study of gastric evacuation or passage of food through the digestive tract is essential to generate information on the digestive physiology of organisms, as they help to quantify the daily ration to avoid any poor diet. In this sense, the present work aims to demonstrate some basic aspects of the fish Dormitator latifrons digestive physiology by evaluating the transit of food through the intestinal tract as a function of time. In a completely randomized standard design, juveniles of D. latifrons were fed ad libitum with commercial pellets. Five conditioned organisms were sacrificed every hour after a single feeding. The food bolus was collected at each sampling point, using polynomial regression models to analyze the passage of food through time in the digestive tract. The passage of food showed a nonlinear behavior in time, being the simple exponential decay model of two parameters (R2 = 0.630; P < 0.0001) the best to explain the evacuation of food through the digestive tract. This knowledge will generate better feeding protocols for this species with commercial importance and aquaculture potential.