ABSTRACT
Catla catla (Hamilton) is one of the fastest growing Indian major carps (IMCs) with increasing market demand. Consistent demand and exploitation invites the attention of ichthyologists for its conservation strategies. Age and growth studies play a pivotal role for managing the fishery stocks in different water bodies. Here, we studied the age and growth patterns using opercula of both farm grown as well as the wild grown C. catla adopting standard methodologies. Wild specimens were caught from Harike wetland (Ramsar site) and the cultivated one from a farm at Dhudike in Punjab. High value of correlation coefficient ‘r’ 0.976 (wetland) and 0.983 (farm) reveals the strong relationship in total length and operculum radius of the fish. C. catla achieved average total length from wetland and farm, respectively at 1st (273.44 mm) 2nd (427.44 mm) 3rd (525.49 mm) 4th (624.52 mm) 5th (744.98 mm) 6th (813.62 mm) and 1st (282.1 mm) 2nd (463 mm) 3rd (601.7 mm) year of age of opercular bones study. The growth parameters such as, index of species average size (?h) 135.6 (wetland) and 200.6 (farm), growth constant (Clt) showed two growth phases from both localities i.e. sexual immaturity up to 2 years and sexual maturity afterwards. Whereas, growth characteristic (Cth) has revealed irregular growth pattern at wetland in comparison to growth of fish from farm. The results of this study concluded that the fish experienced more growth from the farm due to better and controlled conditions but, in wetland surrounding conditions were observed to be unfavourable for survival of the fish C. Catla.
ABSTRACT
In presence of a decrease in the catch from Infiernillo reservoir, Michoacán-Guerrero, Mexico, age and growth of tilapia Oreochromis aureus (Steindachner 1864) were estimated, as indispensable attributes for fishery management. Evaluations included scales and opercular bones readings and length frequency analysis. The population structure was determined too. Due to the great variation of tilapia individual growth and with the objective to have reliable growth estimations, linearized, non-parametric and non-linear methods were used and their applicability discussed. Comparison of ages determined from these methods revealed that opercular bones readings had advantages over scales. Reproduction and competition for space and food were considered as responsible factors for ring-formation on tilapia hard structures. The non-linear method was considered the best for modelling populations highly variable, which is characteristic of tilapia and tropical fish with multiple spawns. The growth parameters estimated were Linfinity = 479 mm, K = 0.46/yr, t0 = -0.055 yr. The tilapia population in Infiernillo reservoir is dominated by juveniles less than 1.5 years old. The fishery activity is affecting the tilapia population growth because are caught when they have not yet spawned. Therefore, this fishery is in urgent need of regulation. Increasing the mesh size of the gill nets might contribute to protect the reproductive potential of the stock.
Ante el continuo decremento en las capturas de tilapia de la presa Infiernillo, Michoacán-Guerrero, México, se estimó la edad y crecimiento de Oreochromis aureus (Steindachner 1864) que son atributos indispensables que deben conocerse para realizar el manejo de la pesquería. La evaluación incluyó la lectura de marcas de crecimiento en escamas y opérculos, y el análisis de frecuencia de tallas. También se estimó la estructura de edad de la población. Debido a la alta variabilidad individual en el crecimiento que presentan las tilapias y a fin de obtener estimaciones fidedignas de crecimiento, diferentes métodos lineales, noparamétricos y no-lineales fueron usados y su aplicación discutida. Los opérculos presentaron ventajas sobre las escamas en la determinación de edad. La reproducción y la competencia por espacio y alimento fueron consideradas factores responsables de la formación de marcas en las estructuras duras de tilapia. El modelo no-lineal fue considerado el mejor para modelar el crecimiento de poblaciones altamente variables como la de tilapia y otros peces tropicales que presentan múltiples desoves. Los parámetros de crecimiento estimados fueron: L∞ = 479 mm, K = 0.46/yr, to = -0.055 yr. La población de tilapia en la presa Infiernillo está dominada por juveniles menores de año y medio de edad. La actividad pesquera está afectando el crecimiento de la población de tilapia, puesto que éstas son capturadas antes de que desoven. La pesquería requiere urgentemente una regulación. Un incremento en la abertura de malla de las redes agalleras con que es capturada, podría contribuir a proteger el potencial reproductivo del stock.