Profile of ectoparasites and biometric condition of snakehead (Channa striata Bloch 1793) collected from different habitats

Studies related to the comparison of ectoparasites that infect snakehead from different habitats and their relationship to biometric conditions have not been widely studied. Thus, present study aimed to investigate the prevalence, intensity, dominance, and predilection of ectoparasites on snakehead collected from ditches, paddy fields, and swamps and correlate them with biometric conditions. In total of 90 snakehead fish were collected from ditches, paddy fields, and swamps. The observation of ectoparasites was performed on the gills, fins, and skin. The parameters measured in this study were ectoparasite profiles and biometric condition of fish. Specifically, the parameters of the ectoparasite profile included prevalence, intensity, dominance, and predilection. Meanwhile, the parameters of the biometric conditions were the length-weight relationship, the distribution of length and weight classes, and condition factors. Five species of ectoparasites that have been identified as Tetrahymena sp., Epistylis sp., Trichodina sp., Dactylogyrus sp., and Gyrodactylus sp. Tetrahymena sp. infection in snakehead was reported for the first time. The ditch habitat had the highest prevalence and intensity, which were 76.7% and 15.4 ectoparasites/fish, respectively. Tetrahymena sp. and Epistylis sp. were detected in sneakhead from all habitats, Trichodina sp. was detected at ditch and paddy field habitats, whereas, Gyrodactylus sp. and Dactylogyrus sp. were only found in swamp habitats. The gill was the predilection organ that most vulnerable to ectoparasite infection. Infected Snakehead tend to have lower average weight and length than healthy snakehead. Snakehead with a weight range of 115.2-145.2 g and a length range of 258.5-268.5 mm tend to be more vulnerable to ectoparasite infection compared to other sizes.Keywords:Tetrahymena sp.PrevalenceIntensityPredilectionLength-weight relationship

Spatiotemporal variations in length-weight relationship, growth pattern and condition factor of Periophthalmus variabilis Eggert, 1935 in Vietnamese Mekong Delta

Length-weight relationship (LWR), growth pattern and condition factor (CF) play a vital role in fish resource evaluation and management but data on this is limited for Periophthalmus variabilis. This is an amphibious fish that lives in the mudflats of the mangrove forests in the Western Pacific regions, including the Vietnamese Mekong Delta (VMD). This paper contributes to the understanding of the LWR, growth pattern and CF of P. variabilis. Fish specimens were collected by hand at four sites in the VMD from April 2020 to March 2021. The analysis of 495 individual fish (259 females and 236 males) showed that fish weight could be estimated from a given fish length due to high determination values (r2 = 0.70 − 0.97). Dusky-gilled mudskippers of the VMD exhibited positive allometry, as indicated by their larger than 3 b value (b = 3.094 ± 0.045, p = 0.04). However, the growth pattern of the mudskipper between the sex and maturation stage (immature versus mature) showed isometry. These fish displayed positive allometry in the dry season (b = 3.138 ± 0.065) (>3, p = 0.04) but isometry in the wet season (b = 3.058 ± 0.061) (≈3, p = 0.34). Fish growth ranged from isometry to positive allometry and varied by site (b = 2.850 ± 0.103–3.370 ± 0.114) and month (b = 2.668 ± 0.184–3.588 ± 0.299) based on the b value. The CF of P. variabilis was not affected by sex (p = 0.29), body size (p = 0.64) or season (p = 0.43), but was affected by site (p = 0.01) and month (p = 0.01). The CF of this species (1.05 ± 0.02) was higher than 1 (p < 0.001), indicating that the fish adapted well to their habitat.

Length-Weight Relationship, Condition Factor and Feeding Habit of Fishes from Mangrove of Santubong Estuary, Sarawak, Malaysia

Length-weight relationship (LWR), condition factor (K) and feeding habits of Coilia dussumieri, Nemapteryx nenga and Nibea soldado from Santubong Estuary, Sarawak, Malaysia were reported in the present study. The sampling was conducted during the non-monsoon season and monsoon season from April to November 2017 at Buntal, Penambir and Demak rivers using three-layered gillnets. A total of 182 fish samples were caught and measured for the total length and body weight. Then, the data were analysed by the equations for LWR and K. The feeding behaviour analysis was carried out using Relative Gut Index (RGI) and Frequency of Food Occurrence method. The log-transformed regression showed that most of the fishes exhibited negative allometric. K showed a significant difference between seasons. The RGI values of the fishes showed that they were carnivorous. The highest frequency of food occurrence in both seasons was gastropods (94-95 %) and the food items were found to be more variable during monsoon season (gastropods insect, worms, fish, asteroidea, phytoplankton and bivalve). The b value is an exponent to measure the growth pattern of fish and in this study, the b values were in the expected range of 2.5-3.5 and not affected by seasonal variation. The K values suggesting that most of the species were surviving well in the river and was influenced by seasonal change. The RGI and frequency of food occurrence showed that all fish in this study species were carnivorous with more variability in food was observed during the monsoon season. The data of this study are important for a sustainable fisheries management in this area.

Relación longitud-peso de la mojarra amarilla Caquetaia kraussii en la Ciénaga de Ayapel, Colombia / Length-weight relationship of yellow mojarra Caquetaia kraussii in the Cienaga de Ayapel, Colombia

Se evaluó el crecimiento y condición de la Mojarra amarilla Caquetaia kraussii (STEINDACHNER, 1878) durante varios ciclos anuales en la ciénaga de Ayapel, Colombia. En el período 2006-2010 se recolectaron 2559 ejemplares y la relación longitud-peso y el factor de condición se estimaron con las ecuaciones WT =k LTb y k =WT/LTb, respectivamente. Se encontró que la Mojarra amarilla es un pez de pequeño tamaño, con tallas entre 14.0-30.0 cm de longitud total (LT), talla media de captura de 20.9 cm LT y peso entre 48.0-598.0 gramos, en donde la mayor parte de los individuos fueron recolectados con longitudes menores a la talla de captura establecida en el país, lo cual indica que no se estaba cumpliendo con la normatividad pesquera vigente, lo que se habría convertido en un problema de sobrepesca. La relación longitud-peso estimada fue WT =0.012 (± 0.05) LT 3.13 (± 0.04), r =0.95, n =2559, el factor de condición fluctuó entre 0.010 (años 2008 y 2009) y 0.035 (año 2006), con diferencias estadísticas significativas y poca correlación con el ciclo hidrológico de la ciénaga; mientras que el coeficiente de crecimiento fue alométrico positivo, oscilando entre 2.76 (año 2006) y 3.23 (año 2009), también con diferencias estadísticas significativas entre ellos. La información evaluada sugiere que la especie no se adaptó a las presiones ambientales y/o antrópicas que influyeron en su crecimiento en la ciénaga; por lo que se le debe prestar especial atención por parte de las agencias pesqueras y ambientales para su ordenamiento pesquero y preservación en el medio natural, apuntando a la seguridad alimentaria de las poblaciones humanas asentadas en la ciénaga de Ayapel.

Size Distribution, Length-Weight Relationship, and Size at Morphometric Maturity of the Mud Spiny Lobster Panulirus polyphagus (Herbst, 1793) in the Johor Strait

Spiny lobsters of the genus Panulirus are economically important and support local fishing communities. However, mud spiny lobster Panulirus polyphagus is among the least known species within this genus in terms of their biological information. This study relates to the size distribution, length-weight relationship, and size at morphometric maturity of P. polyphagus in the Johor Strait. Within the year 2010, 300 specimens were collected off the coast of Johor Strait, Malaysia. There was no significant difference in body size (cephalothorax length, CL) and body weight (BW) between sexes. CL and BW were highly correlated and males of P. polyphagus displayed positive growth allometry, whereas the opposite was observed in females. Based on the merus (ML) and carpus length (CPL) of the third right walking leg, the piecewise linear regression analysis estimated that the size at maturity for male was 6.58 cm CL (based on ML) and 7.58 cm CL (based on CPL), whereas it was 8.18 cm CL (based on ML) and 6.75 cm (based on CPL) for females. Two discriminant functions of high classification and revalidation rates (&gt; 98.6% in males and &gt; 98.7% in females) that can discern maturation status in males and females of P. polyphagus were derived using the discriminant function analysis. Biological information derived from this study serves as an essential baseline for future fishery management and conservation of P. polyphagus.