Journal of Applied Ichthyology最新文献

Cobitis faridpaki is a small endemic loach from the southern Caspian basin. Reproductive parameters are key components for enlightening the life history of an endemic species. The reproduction parameters of C. faridpaki including sex ratio, spawning season, fecundity, and oocyte diameters were studied in a tributary of Gorganroud River – northern Iran, the area where no information on the Cobitis spawning is available, from February to July 2018. A total of 403 specimens including 47.8% males and 52.2% females were collected using electrofishing. Even though the sex ratio was not significantly different from parity, a perceptible dominance of females in the pre-spawning and spawning periods could be observed in the population. Based on the monthly variation in GSI, the spawning period is from late March to early May. The absolute fecundity of females ranged from 57 to 1287, with a mean of 404 (±250) oocytes per ovary, and relative fecundity was estimated to be 47–386, with a mean of 136 (±73) oocytes per gram of total weight. Absolute fecundity established statistically significant linear relationships with total length and weight. Oocyte diameters varied from 0.26 to 1.30 mm, being of multi-modal distribution throughout the spawning period, which suggests that the species is a multispawner. The oocyte size correlated positively with the length, weight, and age of mature females. This study provides fundamental information to aid in future conservation programs that intend to reduce the ongoing depletion of habitats and populations of endemic species.

Length-weight and length-length relationships (LWRs and LLRs) for eight species of sharks were estimated using fish specimens caught in commercial fishery during 2018–2021 and landed at three fishing ports (Tanjung Luar Fish Landing Port-Lombok, Muncar Coastal Fishing Port-Banyuwangi and Sungai Kakap Fish Landing Port-Pontianak). The LWRs for Hemipristis elongata, Lamiopsis tephrodes and Pseudocarcharias kamoharai as well as the LLR for P. kamoharai reported in this study have not appeared on FishBase. This study also improved the LWRs and LLRs for other species. In addition, this study updated the maximum total length records for Carcharhinus brevipinna, Hemigaleus microstoma, H. elongata, Hexanchus nakamurai and L. tephrodes.

Recent studies have incorporated behavioural aspects into the analysis of animal invasion processes, citing high activity and boldness as typical traits of successful invaders. The topmouth gudgeon Pseudorasbora parva is arguably the world's most widespread freshwater fish invader currently listed as a pest species on the list of invasive alien species of Union concern. The study aimed at elucidating whether behavioural traits of P. parva contribute to its invasive success. Laboratory experiments contrasting P. parva activity levels, habitat choice and boldness with that of native competitors Eurasian perch Perca fluviatilus and three-spined stickleback Gasterosteus aculeatus showed P. parva to be relatively shy and avoiding direct competition for prey. An additional field study in a pond in central Germany demonstrated that P. parva was able to establish and maintain a small population, co-existing with a much higher density of P. fluviatilis. The study suggests that the invasive success of P. parva may be a result of its flexible life-history traits, while behavioural traits such as boldness and competitive dominance for food may only play a minor role.

High density fingerling rearing of pengba, Osteobrama belangeri in biofloc system was carried out for 45 days with wheat flour and molasses as two carbon sources to maintain C/N ratio of 15:1. Effect of biofloc was evaluated in terms of water quality changes, fish growth performance, digestive enzyme activities, non-specific immune system and antioxidants enzyme activities. Use of the two carbon sources ensured prevalence of better growing environment, higher digestive and antioxidant enzymatic activities, ultimately leading to higher fish growth, as compared to control. Further between the two carbon sources, use of wheat flour caused significant increase in the activities of digestive enzymes, amylase and total protease (p < .05); antioxidant enzymes such as SOD and catalase; increase in serum total protein, albumin and globulin, as compared to molasses, ultimately leading to higher growth. However, non-specific immune parameters such as respiratory burst activity in blood, lysozyme activity, and myeloperoxidase activity in serum were higher (p < .05) in fish reared with molasses. Such result while indicated benefits of additional carbon source, it also revealed wheat flour to be a better source for carbon supplementation than molasses in biofloc system during the high-density fingerling rearing of O. belangeri.

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.