Effects of climate and land-use changes on fish catches across lakes at a global scale

Globally, our knowledge on lake fisheries is still limited despite their importance to food security and livelihoods. Here we show that fish catches can respond either positively or negatively to climate and land-use changes, by analyzing time-series data (1970–2014) for 31 lakes across five continents. We find that effects of a climate or land-use driver (e.g., air temperature) on lake environment could be relatively consistent in directions, but consequential changes in a lake-environmental factor (e.g., water temperature) could result in either increases or decreases in fish catch in a given lake. A subsequent correlation analysis indicates that reductions in fish catch was less likely to occur in response to potential climate and land-use changes if a lake is located in a region with greater access to clean water. This finding suggests that adequate investments for water-quality protection and water-use efficiency can provide additional benefits to lake fisheries and food security

Evaluation of the fishery of the brown shrimp Penaeus aztecus of the mexican littoral of the northwest Gulf of Mexico

Stock assessment of the brown shrimp (Penaeus azteca) from the northwest Gulf of Mexico is developed using monthly data from commercial catches from 1974 to 1982. Growth parameters from the von Bertalanffy equation were as follows: Kmin = 0.142 m–1 to Kmax = 0.1812 m–1; L∞min = 214 mm to L∞max = 236 mm. Mortality rates were obtained directly from the identified cohorts through the catch curve and the weighted average of the amount of fishing applied on each cohort; results were as follows: total mortality, Zmin(1981) = 0.8494 to Zmax(1974) = 1.240; fishing mortality, Fmin( 1981) = 0.3786 to Fmax(1974) = 0.646; and natural mortality, Mmin(1978) = 0.415 to Mmax(1974) = 0.594. Catchability estimations mere: qmin(1975) = 0.0012 to qmax(1978) = 0.0021. Exploitation rate indicates a reduction of 30% of the fishing intensity, for the last two years, compared with the previous ones. From these years (1981 and 1982), fishery was acting under the maximum sustainable yield level

Probability sampling design for the artisanal fishery of the red grouper (Epinephelus morio) Off Yucatan, Mexico

The purpuse of this paper is to propose an optimum sampling design using probabilistic techniques to obtain estimators of the average weight of fishes, total number, proportion and number of individuals per length class, and the respective variances. A sampling design based on two strata composed of the ports on both the east and west coasts of Yucatán is suggested, which are separated mainly by the size of fishes within the capture. Within each strata, a three-stage sampling design was defined with primary units (ports), secondary units (boats) and tertiary units (fishes), and their variances obtained. A sample size was fixed for each port, and an optimum sample size for secondary and tertiary units is calculated using the graphical method proposed by Chester and Waters