Journal of Applied Ichthyology最新文献

Increasing the number of fish stocked might optimize the efficiency of intensive aquaculture systems however at the same time might have a negative impact on fish welfare and growth parameters. In the current study, three different stocking densities were evaluated in duplicated tanks to investigate the effect of different stocking densities on the survival and growth of sterlet larvae from hatching until the end of weaning, during the 30-day trial. Tested densities were 5, 10, and 20 larvae L⁻¹ in the low (L), medium (M), and high (H) density group, respectively. Freshly hatched larvae (1250, 2500, 5000 larvae per duplicated tanks) were divided into three treatment groups in 250 L raceway larval rearing tanks. The fish biomass gain was significantly higher in each group of higher stocking densities (0.2 ± 0.0 g L⁻¹; 0.4 ± 0.0 g L⁻¹ and 0.8 ± 0.1 g L⁻¹ respectively, r = .990, p < .001). The L group showed a tendency towards better growth during the first 3 weeks, however, at the end of the trial, no significant differences were observed. The highest mortality at the start of exogenous feeding was noticed in group H (12.77% ± 1.3%) and was significantly different from the two lower density groups (5.16% ± 1.3% in L, 7.94% ± 1.3% in M), however, the overall mortality at the end of the trial did not differ among groups. Results on both growth and mortality during the later periods are suggesting the adaptability of sterlet larvae to the more intensive rearing conditions. Thus, it can be stated that the application of a stocking density of 20 larvae L⁻¹ is appropriate in the initial period of larval rearing in the sterlet.

Invasions of non-native fish species are generally associated with human activities that violate historically insurmountable barriers to species on local and global scales. For Pterygoplichthys ambrosettii (Holmberg 1893), invasive to the upper Paraná River basin, informations about introduction and period of occupation are uncertain. Thus, aim of this study was to establish the invasion chronology and the establishment of this species in the Upper Paraná River basin, based on long-term data (37-year sampling), in addition to evaluating its current distribution. The results indicate that P. ambrosettii was first recorded in 1997 in the Itaipu reservoir and in 2000 in the Upper Paraná River floodplain. Currently, this species is registered in 118 localities in the basin, and the fact that several of these occurrences were recorded in locals that are not accessible through upstream migration suggests their origin from the aquarium hobby. This study elucidates when and where the invasion process of by P. ambrosettii began in the Upper Paraná River floodplain, and indicates that its broad non-native distribution has exceeded the limits imposed by the geographical barriers.

The Pallid Sturgeon (Scaphirhynchus albus) Conservation Propagation and Stocking Program began stocking in the Missouri River above Fort Peck Reservoir in 1998 with 1997-year-class pallid sturgeon. Within the 1997-year class, all hatchery-origin pallid sturgeon females that reached reproductive maturation by 2016 underwent mass ovarian follicular atresia. Using combined historical and contemporary data, we described the spawning periodicity for female and male pallid sturgeon, characterized age- and size-at-first spawning, and evaluated what proportion of females experience mass ovarian follicular atresia during the first and subsequent reproductive cycles. Pallid sturgeon reached their first reproductive cycle at older ages and larger sizes than described for other populations. Females were functionally and physiologically capable of spawning at 21 years and males at 15 years. Immature pallid sturgeon as old as 20 years were documented. We found that more female pallid sturgeon underwent mass ovarian follicular atresia during the presumed-first reproductive cycle or known-first reproductive cycle than females during subsequent reproductive cycles (62.5% compared to 33.3%) indicating that effects related to reproductive maturation may be occurring. Nonetheless, mass ovarian follicular atresia appears to also occur for reasons not related to reproductive maturation. Females had biennial reproductive cycles, and males had annual and biennial reproductive cycles. Population models should account for females undergoing mass ovarian follicular atresia in their first reproductive cycle and subsequent cycles thereby increasing the age at first-successful spawning and reducing the estimated size of the spawning stock.

It has been well documented that circle hooks generally reduce deep hooking of bait-caught fish. However, for decades there has been speculation that the hook eye must be straight relative to the shank for circle hooks to function properly, yet this aspect of hook configuration has rarely been investigated. Using a passive hook set when strikes were detected, we compared deep hooking rates and catch probability for stream-dwelling trout (Yellowstone cutthroat trout [Oncorhynchus clarkii bouvieri Jordan & Gilbert], rainbow trout [O. mykiss Walbaum], and cutthroat trout × rainbow trout hybrids) caught using baited circle and J hooks with the eye either straight with or turned-up from the shank. Landed fish averaged 26 cm in total length and ranged from 11 to 46 cm. Most fish (83%) were hooked either in the upper or lower jaw, but 16% were hooked deeply (i.e., either in the esophagus or the gills). As expected, the deep hooking rate was lower for circle hooks (10%) than for J hooks (24%). Logistic regression model results indicated that hook eye orientation had no effect on deep-hooking, with deep hooking rates of 11.0% and 8.2% for circle hooks with angled-up and straight eyes, respectively, compared to 21.7% and 25.3% for J hooks with angled-up and straight eyes. Model results also revealed that deep hooking probability differed among anglers but did not differ between species and was not related to fish length. Catch probability (i.e., the proportion of fish strikes that resulted in a landed fish) did not differ between hooks or hook eye orientations. Contrary to some perceptions, our results suggest that changing the angle of the hook eye does not affect deep hooking rates when anglers use baited circle hooks to land stream-dwelling trout.

Common hairfin anchovy (Setipinna tenuifilis) is an economically and ecologically important pelagic fish in China's seas. However, the resources of S. tenuifilis have been greatly declined as a result of overfishing. Therefore, a large number of polymorphic molecular markers will be of benefit to a further investigation of the existing genetic resources. In this study, a total of 2,529,301 microsatellite loci were detected in the S. tenuifilis genome using third-generation sequencing technology. Seventeen microsatellite markers were successfully developed from the randomly selected 100 dinucleotide motifs and genotyped by capillary electrophoresis. Sixteen markers were detected to be high polymorphic (PIC > 0.5) in S. tenuifilis. The number of alleles (Na) and effective number (Ne) of alleles ranged from 8 to 29 (mean 18.471) and ranged from 2.149 to 19.619 (mean 9.921), respectively. The average Ho was 0.642 and ranged from 0.383 to 0.900, and the average He was 0.855 and ranged from 0.535 to 0.949. The PCoA result showed no significant genetic heterogeneity based on individual genetic distance. However, the analysis of the STRUCTURE displayed a discontinuity between northern and southern populations. The result showed that these polymorphic microsatellite markers could be applied to study genetic diversity and population differentiation of S. tenuifilis, facilitating the management and conservation of this species.

A 60 days growth trial was conducted with fry of Hypselobarbus pulchellus for evaluating the effect of incorporation of two aquatic plants Azolla microphylla and Vallisneria spiralis at 30, 60 and 90% levels in the diet on growth and survival. The fry (average weight 23.07 ± 0.96 mg and average length 1.57 ± 0.24 cm) were stocked at 12 numbers per tank and fed to satiation with one of the experimental diets (three diets each with azolla and vallisneria) or a control diet. Water quality parameters analysed at fortnightly intervals did not show significant difference between treatments (p > .05). The mean final weight of fish reduced in groups fed diets with azolla and vallisneria incorporated beyond 60% and 30% respectively (p < .05). While the mean final length of fish fed azolla diets did not differ among the treatments, it gradually reduced in groups fed diets with increasing levels of vallisneria incorporation (p > .05). The condition factor and survival did not vary between treatments (p > .05). The study indicates the possible incorporation of azolla up to 60% and vallisneria up to 30% as feed ingredients in the diet for H. pulchellus during fingerling raising.

In this study, we present a taxonomic synthesis and compendium of the diversity and distribution of stonefishes of the genus Minous (Scorpaeniformes: Synanceiidae) from Indian waters, including revised species descriptions, diagnoses, and biometric data from specimens off the coast of Visakhapatnam, central eastern India. A total of 342 Minous specimens (males, females, and juveniles) from Visakhapatnam waters were examined and identified based on external and internal morphology, resulting in the identification of four Minous species: M. coccineus Alcock 1890, M. inermis Alcock 1889, M. monodactylus (Block and Schneider 1801), and M. trachycephalus (Bleeker 1855); the last-named recorded for the first time in Indian coastal waters. Furthermore, the study reports the occurrence of M. inermis (Alcock's scorpionfish) from coastal waters of Visakhapatnam for the first time. Finally, we present a taxonomic key for the identification of the species of Minous present in Indian waters.

From experimentations in optimal conditions, we identified the main features of embryogenesis of allis shad Alosa alosa. We propose to use this outcome as endpoints to evaluate the impact of stressors on A. alosa embryogenesis in future studies. Eggs are spherical in shape, transparent and non-adhesive. Mass hatching occurs between 120 and 144 hpf at an incubation temperature of 20°C. Abnormalities of larvae were minor (1.10% of hatched individuals).

The capture of a female specimen of the velvet belly lantern shark Etmopterus spinax with abnormal skin coloration is reported. The specimen was captured off northern Spain (Bay of Biscay, North-eastern Atlantic) in 2021 by bottom trawling. The lack of dermal melanophores combined with a normal retinal pigmentation, lead us to considerate the specimen as leucistic. This is the first case of leucism in E. spinax and the second record of colour aberration in the family Etmopteridae. A comprehensive updated review of published literature on albinism and leucism in chondrichthyans is also provided.

The length-weight relationships were estimated for three reef fish species caught in the Gulf of Mannar, India using experimental longlines. The longline fishing took place from December, 2019 to September, 2021 in fortnightly intervals, using longlines (2400 m, 2700 m and 3360 m each), equipped with each 600 various “J” type fishing hooks (straight, reversed, kirbed). The hook sizes used were standard size numbers 6, 9, and 12. The longlines fabricated with polyamide monofilament line were operated from 20 to 50 m depth for 3–5 hours each time. Overall, 81,000 hooks were deployed in 45 fishing trials. The total length and total weight of the combined sex group was recorded nearest to 0.1 cm and 0.01 g, respectively. By using the logarithmic transformed data, linear regression analysis was performed to calculate a and b values for three fish species to establish length-weight relationships. The parameters for the length-weight equations for three species are provided along with respective coefficient of correlation and the 95% confidence intervals. A new maximum total length was recorded for two grouper species, viz., Epinephelus faveatus (36.5 cm) and Cephalopholis urodeta (46.0 cm).