LENGTH-WEIGHT RELATIONSHIP AND RELATIVE CONDITION FACTOR OF 31 SMALL-SIZED FISHES OF THE PARANAPANEMA RIVER BASIN

Studies on length-weight relationships are of great importance in fishery assessments. These studies are substantial to evaluate fish population dynamics, and in communion with the relative condition factor, could provide an estimation of potential acting environmental conditions. In this paper, we evaluated the length weight relationship and relative condition factor of small sized fish species. Fish were sampled quarterly between the years 2012-2013 and 2018-2020 in lagoons and tributaries of Rosana and Taquaruçu reservoirs, located at the lower Paranapanema River basin, Brazil. The standard length (SL) in millimeters and weight (W) in grams were measured, and the length-weight relationship was calculated using linear regression analysis (W = log (a) + b log (SL)). After, the relative condition factor (Kn) was calculated from the expression We = a.SLb. Thus, the length-weight relationships of 31 species were calculated in each environment considered, giving rise to 74 population allometric coefficients (b) and relative condition factors (Kn). As result, 24 b coefficients were concentrated between 2.5 and 3.5 and seven were out of the confidence interval, while the 74 Kn values demonstrated close to the central mean and not statistical different. Our results are relevant to the conservation of fish fauna, improving knowledge regarding small-sized fish and those living environment.

Interpreting Daly’s Sustainability Criteria for Assessing the Sustainability of Marine Protected Areas: A System Dynamics Approach

Sustainability assessments of marine protected areas (MPAs) are essential for improving the effectiveness of management efforts. Since sustainability is closely related to the concept of intergenerational well-being, measuring and tracking it through time is crucial. Therefore, this study will use the system dynamics approach applied at Pieh marine park as the study site. A system dynamics model was built comprising four sub-models: fish population dynamics, coral reef coverage, tourism, and pollution. The goodness-of-fit test of the model indicated low and unsystematic model error. The sustainability assessment was conducted using the three principles of sustainability proposed by Herman Daly, which define sustainability for resource management based on the change in the amount of renewable resources, non-renewable resources, and pollution. The sustainability assessment determined that Pieh marine park cannot sustain economic activities in its area, indicated by decreasing renewable resource indicators in the form of fish population dynamics, coral reef coverage, and increasing pollution levels. Several management interventions can be applied to improve sustainability, including lowering the total allowable catch, coral transplantation, and improved waste management.

Continuous learning, teamwork, and lessons for young scientists

This paper describes my research on fish population dynamics, which has aimed to improve the information available for management and conservation. Through numerous collaborations, my research program addressed three main objectives. (1) Increase the understanding of spatial and temporal variation in productivity of fish populations. (2) Quantify uncertainties and risks in fishery systems and their implications for management and conservation. (3) Develop methods to reduce those uncertainties and risks. To help young scientists, I present 11 general lessons, as well as some specific advice, that emerged from that research. The general lessons include pursuing a path of continuous learning, going beyond your comfort zone to broaden your skills and knowledge, and collaborating with others. More specific advice for fisheries scientists includes evaluating the bias and precision of parameter estimation methods via Monte Carlo simulations, and considering multiple models of whole fishery systems. This paper also illustrates, with examples, how the understanding of some aspects of fish population dynamics has evolved, at least from the limited perspective of my own group's research.