Age and growth changes and population dynamics of the black pomfret (Parastromateus niger) and the frigate tuna (Auxis thazard thazard), in the Taiwan Strait

Abstract

With five age groups of each, the dominant black pomfret was one year, while frigate tuna was two years. The total mortality coefficient (Z) and the fishing mortality (F) of the black pomfret were at high levels, the exploitation ratio (E) was over 0.5, and the number of captured juvenile fishes showed that the stock of black pomfret in this area was overexploited and improper fishing gear was utilized.Compared with previous studies, the maximum and mean fork length, body weight and age of the two fishes declined gradually, the populations were younger in age and smaller in size. The growth coefficient k increased and age at the inflexion point of weight t r was younger than before. The smaller change of the fork length at first maturity of the two fishes has indicated a more vulnerable fishery ecosystem in this area. Therefore, in addition to the traditional fishery management approach, such as taking the minimum length into consideration, ecosystem approach to fisheries management (EAF) should be taken to improve the practical fishing management, including conserving the small pelagic fishery population in order to achieve the sustainable fishing of the stocks. Keywords: Parastromateus niger, Auxis thazard thazard, age, growth, population dynamics, management, Taiwan Strait, China.Cambios en la edad y el crecimiento y dinámica poblacional de la palometa negra (Parastromateus niger) y del atún fragata (Auxis thazard thazard), en el estrecho de Taiwán RESUMEN. La edad y crecimiento de la palometa negra, Parastromateus niger y del atún fragata o melva, Auxis thazard thazard se estudiaron a partir de especímenes capturados mensualmente en el estrecho de Taiwan, entre abril 2005 y marzo 2006. Se determinaron cinco grupos de edad, siendo dominante en la palometa negra los ejemplares de un año, mientras que en el atún fragata los de dos años. El coeficiente de mortalidad total (Z) y la mortalidad por pesca (F) de la palometa negra se encontraron en niveles altos. La tasa de explotación E resultó sobre 0,5 y el número de peces juveniles capturados demuestra que la población está sobreexplotada en la región y los equipos de pesca utilizados resultan inadecuados. En comparación con estudios previos, la longitud horquilla máxima y media, el peso corporal y la edad en ambas especies ha disminuido en forma gradual, presentando las poblaciones peces de menor edad y tamaño. El coeficiente de crecimiento k aumentó y la edad en el punto de inflexión en peso t r se obtuvo en ejemplares más jóvenes que en años previos. El pequeño cambio de la longitud horquilla determinado en la primer madurez en las dos especies indica que en esta zona, el ecosistema pesquero se encuentra más vulnerable. Por eso, además del enfoque tradicional en la gestión de la pesca, como la adopción de una longitud mínima, se requiere adoptar el enfoque ecosistémico a la ordenación de la pesca (EEP) para mejorar la conservación de la población de pequeños pelágicos y lograr así el desarrollo sostenible de los recursos pesqueros. Parastromateus niger and Aux...

Short Communication: Growth and mortality rate of Black Pomfret Parastromateus niger (Bloch, 1795) and Silver Pomfret Pampus argenteus (Euphrasen, 1788) in Paloh Waters, West Kalimantan, Indonesia

“…The results of these two studies indicated that the species had the growth rate higher than 0.5 year -1 . The growth rate of P. niger in Taiwan Strait and West Coast of India were 0.3157 year -1 and 0.73 year -1 , respectively (Tao et al 2012;Khan et al 1992). The age of P. niger in Iranian Coast of Oman Sea was determined at the age 1 to 6-year-old fish based on otolith cross sections (Yadollahvand and Rahnama 2014).…”

Age, growth, mortality and population structure of silver croaker Pennahia argentata (Houttuyn, 1782) and red bigeye Priacanthus macracanthus Cuvier, 1829 in the north-central Taiwan Strait

“…Specific ecological factors, such as population density, environment temperature, and prey density, may cause growth parameters for the two species to vary in different sea areas. Compared with previous studies in the Taiwan Strait (Zhang, 1987;Lu et al, 1999a,b), the population structures (Table 3) and ecological characteristics (Table 5) of these two species have changed in recent decades, indicated that the populations of the two species were younger, smaller and earlier in sexual maturity, similar to that of other demersal fishes such as the little yellow croaker Larimichthys polyactis (Bleeker, 1877) (Chen et al, 2010), black pomfret Parastromateus niger (Bloch, 1795), and the bullet mackerel Auxis thazard thazard (Lac ep ede, 1800) (Tao et al, 2012) in the north-central Taiwan Strait.…”

Evaluating Stock Status of 16 Commercial Fish Species in the Coastal and Offshore Waters of Taiwan Using the CMSY and BSM Methods

“…Meanwhile, coastal and offshore catches have decreased from 408,000 t in 1980 to 198,000 t in 2018 (Fisheries Agency, 1949-2019; Figure 2). Among the other stocks affected were P. anomala (Du et al, 2010), P. argentata (Ju et al, 2016), P. macracanthus (Ju et al, 2016), and P. niger (Tao et al, 2012), occurring in the western Taiwan waters (Taiwan Strait), and which became overfished by the 2000s. These fish species belong to Taiwan's most important economic species.…”