A passive integrated transponder tag implanted by a new alternative surgical method: effects on the oriental weather loach (Misgurnus anguillicaudatus) and application in a small irrigation system

We validated the effects of a passive integrated transponder (PIT) tagging process on the oriental weather loach Misgurnus anguillicaudatus. Laboratory experiments were conducted to assess the effects of PIT tagging on fish survival, growth, wound healing, and tag omission. Two tagging protocols, standard syringe injection versus insertion through a small hole pierced by a fine needle-shaped awl, were compared using a 12.5 × 2.07 mm² tag. A control group was also included. In comparison with the awl technique, syringe injection heightened the mortality of the loach and delayed healing of the wound caused by tag insertion. No effects of either PIT tagging method were detected on the growth of surviving loach. We also field-tested similarly tagged populations within a river-based irrigation system of Sado Island, Japan. Two different sized tags (long, 12.5 × 2.07 mm²; short, 8.5 × 2.12 mm²) were compared by using antenna loggers which detected fish movement through gates and automatically logged tagged fish’s tag IDs and timestamps. By comparing logged data and actual fish collection surveys both below and above the gates, 77% and 30% of actual loach movements were confirmed to have been successfully logged for the long and short tags, respectively. The awl insertion technique with the longer tag is therefore recommended for use in similar studies of smaller fish species.     

Effects of acoustic tagging on juvenile green sturgeon incision healing,swimming performance,and growth

Ultrasonic telemetry is a preferred method for fish-movement studies. Despite surgical tag implantation being the most common method for affixing tags, many studies lack tests addressing the assumption that tagging has no effect on fish performance or survival. The threatened, anadromous green sturgeon, Acipenser medirostris, has little documentation concerning its movements. We evaluated the effects of surgery and tag implantation in juveniles. We compared three groups: tagged fish with dummy transmitters implanted in the peritoneal cavity, sham fish that underwent surgery without tag implantation, and control fish that were handled and anesthetized but did not undergo surgery. We found no differences in growth or critical swimming velocity among groups. Photos of incisions were taken towards the beginning and at the end of the study to assess inflammation and to score each incision for closure and suture retention. Inflammation declined similarly for tagged and sham fish during the study. U_crit was not related to the extent of inflammation or to post-surgery time. All fish showed healing during the study (ca. 140 day duration) and 10 % of tagged and sham fish showed signs of inflammation by the study end. These results suggest that current ultrasonic surgical tagging methods do not significantly affect the short-term growth or swimming performance of juvenile green sturgeon. Additionally, effects of surgery can be mitigated by minimizing the number of suture entry points and by using rapid-absorbing sutures.     

Contents of Trace Elements as Indicators of Ecological Divergence between Sympatric Spined Loaches (Teleostei,Cobitidae) from the Upper Dnieper

The contents of eight trace elements (Ti, Mn, Ni, Cu, Zn, Sr, Ba, and Pb) in muscles of syntopic sexual and clonal spined loaches (the golden loach Sabanejewia baltica, diploid males and females of Cobitis taenia, and congeneric triploid clonal females) from the upper Dnieper River and in the syntopic spined loaches (males and females of C. melanoleuca and males of C. taenia) from the upper Volga River basin were determined using the X-ray fluorescence spectroscopy technique. The contents of Cu in the clonal triploid Cobitis females and diploid C. taenia females from the Dnieper are different. The intersexual differences in the contents of Pb and Zn between C. taenia males and females, as well as the interspecific differences in the content of Ti between the spined loaches from the Dnieper and Volga basins were revealed. The concentrations of Cu and Pb correlated with the individual fish size. The potential for the use of the revealed differences in the trace element contents as an indicator of the divergence of ecological niches in the syntopic spined loaches is discussed.     

Evolutionary ecology of clonal-bisexual complexes in spined loaches from genus <Emphasis Type="Italic">Cobitis</Emphasis> (Pisces,Cobitidae)

The objective of this work was to analyze several aspects of evolutionary ecology of the spined loach clonal-bisexual complexes. This analysis demonstrates that the twofold population growth rate in clonal forms compared with bisexual species is not a proper feature of spined loaches, because their clonal forms are polyploids with the larger eggs and correspondingly the lower individual fecundity. Both the larger nutrient stores in eggs and the larger hatchlings provide certain ecological advantages for clonal spined loach triploids at early stages of their ontogeny and possibly ensure the higher fitness in a local environment. The clonal-bisexual spined loach complexes have reduced structure usually including one bisexual species and the only clonal form. This reduction may be caused by several factors: 1) the competition between different forms and subsequent superseding of some of them; 2) a particular manner of colonization of new areas by different bisexual and clonal forms; 3) the absorption of one of parental species for hybrid origins of clonal forms (hypothesis of absorption). The relative numbers of bisexual and unisexual forms in different clonal-bisexual complexes depend on “family ties” between clonal forms and “host” bisexual species; their ratios are subjected to temporal dynamics caused by both external (environmental changes) and internal (automatic fluctuating) factors.     

Tag retention and survival of juvenile bighead carp implanted with a dummy acoustic tag at three temperatures

Bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix (together, the bigheaded carps) are invasive fishes in North America that have resulted in substantial negative effects on native fish communities and aquatic ecosystems. Movement and behavior of adult bigheaded carps has been studied previously using telemetry, while similar studies with juvenile bigheaded carps have yet to be attempted. Recent technological advances in telemetry transmitters has increased the availability of tags sufficiently small enough to implant in juvenile carps. However, the effects of surgical implantation of telemetry tags on juvenile bigheaded carps have not been evaluated. We determined tag retention and survival associated with surgical implantation of acoustic telemetry tags into juvenile bighead carp (range 128–152 mm total length) at three temperatures (13, 18, and 23°C). In addition, we assessed the effect of surgically implanted transmitters on the fitness, defined as changes in weight or critical swimming speed, of carp implanted with transmitters. Survival was high among tagged fish (85%) with 47% of tags retained at the conclusion of the 45‐day study. No substantial decline in fitness of the fish was observed in tagged fish compared to untagged fish.     

Movements and Site Fidelity of two Juvenile Fish Species Using Surf Zone Nursery Habitats Along The Southeastern North Carolina Coast

We examined the extent of movements of juvenile Florida pompano, Trachinotus carolinus, and gulf kingfish, Menticirrhus littoralis, along an open ocean beach. Fishes were collected by seine at three sites along Masonboro Island and Carolina Beach, NC between 7 June and 7 July 1995. All specimens 40 mm standard length (SL) were tagged with coded wire tags and released at the capture sites. Between 7 July and 9 August and on 15–16 September Masonboro Island and northern Carolina Beach were surveyed for tagged fish. A controlled tag mortality/retention study was conducted for both species. Overall, 1569 Florida pompano (40–135 mm SL) were tagged. Sixty-one (3.9%) of these were recaptured, and only eight moved away from the original tagging sites. The largest movements by two Florida pompano were 2.1 and 10.5 km. Many fish remained at their original tagging sites for 21–27 days. Of 488 gulf kingfish (36–158 mm SL) tagged, 16 (3.3%) were recaptured. Gulf kingfish also exhibited little movement away from tagging sites during the study, with individuals remaining at original tagging sites up to 21 days. Stock size estimates for Florida pompano ranged from 3354 to 4670 among the tagging sites, with densities ranging from 1.9 to 2.6 fish m^–2. The remarkable site fidelity exhibited by these two species suggests that resources were not limiting or that predation pressure was not high enough to cause large scale movements during the study. This implies that local disturbances could impact behavior or survival of juvenile fishes in the surf zone.     

Movements and growth of tagged young-of-the-year Atlantic croaker (Micropogonias undulatus L.) in restored and reference marsh creeks in Delaware Bay, USA

The residence time, movements, and growth of tagged young-of-the-year Atlantic croaker, Micropogonias undulatus L., were studied from July to October 1998 as measures of the success of a marsh restoration project adjacent to Delaware Bay. A total of 8173 croaker (41-121 mm SL) were tagged from each of two creeks in both marshes during July and August with internal sequential coded wire microtags. A prior tag-retention study in the laboratory found a 95% tag retention rate. Of those tagged, 3.6% were recaptured within and nearby the study creeks using seines, otter trawls, and weirs during a 105-day period. Recapture percentages ranged from 1.5% to 6.1% in individual creeks in the restored marsh. There was some movement of tagged fish between creeks in the restored marsh and out into the main creek, but 95% of the recaptures were made in the subtidal and intertidal portions of the same creek in which they were tagged. Fewer fish were recaptured at the reference marsh (1.6% recapture; n=1489 tagged) up to 50 days after tagging, with no evidence of movement between creeks. The average individual growth rates for recaptured croaker was the same in both restored (0.69 mm/day) and reference (0.63 mm/day) marshes before egress from the creeks in September and October. As a result, both created creeks in a restored marsh and natural creeks in a reference marsh appeared to be utilized as young-of-the-year habitat in a similar way during the summer and until egress out of the marshes during the fall, thus this restoration effort has been successful in creating suitable habitat for Atlantic croaker.     

Tag retention and mortality of adult Atlantic salmon Salmo salar gastrically tagged with different sized telemetry transmitters

A batch of 1 sea winter pre‐spawning adult Salmo salar from the Bush river in Northern Ireland, U.K., were gastrically tagged with large (13 mm diameter) and small (9 mm diameter) dummy acoustic telemetry tags alongside untagged control fish. Survival differed between control and tagged fish and the estimated probability of survival by the end of the study for control fish with no tag was 0·94, small tags was 0·90 and large tags was 0·72. Tag loss through regurgitation was slightly higher for fish tagged with larger tags than for fish tagged with smaller tags and the estimated probability of tag loss for fish with a small tag was 0·10 and for large tags was 0·14.     

Empirical analysis of the influence of swimming pattern on the net energetic cost of swimming in fishes

We tested the hypothesis that the energetics of swimming in a flume accurately represent the costs of various spontaneous movements using empirical relationships between fish swimming costs, weight, and speed for three swimming patterns: (1) 'forced swimming' corresponded to movements adopted by fish forced to swim against a unidirectional current of constant velocity; (2) 'directed swimming' was defined as quasi-rectilinear movements executed at relatively constant speeds in a stationary body of water and (3) 'routine swimming' was characterized by marked changes in swimming direction and speed. Weight and speed explained between 76% (routine swimming) and 80% (forced swimming) of net swimming cost variability. Net costs associated with different swimming patterns were compared using ratios of model predictions (swimming cost ratio; SCR) for various weight and speed combinations. Routine swimming was the most expensive swimming pattern (SCR for routine and forced swimming =6.4 to 14.0) followed by directed (SCR for directed and forced swimming =0.9 to 2.8), and forced swimming. The magnitude of the difference between the net costs of forced and spontaneous swimming increases with movement complexity and decreases as fish weight increases.     

Effects of tag and suture type on survival and growth of brown trout with surgically implanted telemetry tags in the wild

To test the effects of surgical implants with or without external antennae, 188 wild brown trout Salmo trutta , 150–290 mm, were tagged and released in a small river in May 2005. After 5 months, 103 of the fish were recaptured and examined. Thus, information on the relative survival, growth and general condition of each fish was obtained. The relative survival did not differ between the three groups (control, antennae and no antennae), but the specific growth of the two tagged groups were lower than that of the control fish. The tag:body-mass ratio had a significant negative effect on specific growth. A relative high occurrence of tag expulsion was observed in both treatment groups (23%). The probability to expel a tag was correlated with the tag:body-mass ratio. Finally, the relative survival, growth, expulsion rate and general condition were compared between fish tagged with different types of suture material (absorbable v . non-absorbable). The results show only minor differences, but absorbable suture provided better wound healing and fewer expulsions.     

Effects of surgically implanted transmitters on swimming performance, food consumption and growth of wild Atlantic salmon parr

Experiments were conducted on wild Atlantic salmon Salmo salar parr to determine the effect of surgically implanted dummy transmitters on swimming performance, food consumption and growth. Swimming performance of tagged fish (tag 1·7–3·7% of fish mass) was similar to that of control fish 1, 5 and 10 days after surgery. Negative effects on growth, however, were found up to day 36 of a 45 day experiment (tag 0·9–2·6% of fish mass). Consumption rates were similar between tagged and control fish and did not explain differences in growth.     

Fin-spines attachment,a novel external attachment method for the ultrasonic transmitters on hard fin-spines fish (Sparidae)

The purpose of this study was to develop a novel method for the external attachment of ultrasonic transmitters on hard fin-spines fish (Sparidae). Acanthopagrus latus, one of the main stocking Sparidae fishes in the northern South China Sea, was employed to conduct the 40-day tank experiment by using dummy ultrasonic transmitters. The experiment consisted of 3 treatment groups, i.e., drilling on dorsal fin-spine (DD) group, drilling on anal fin-spine (DA) group, and control (C) group, with each group having 3 replicates and 30 fish per replicate. The feasibilities of DD and DA for the external attachment of ultrasonic transmitters were tested and evaluated using parameters: the specific growth rate, survival rate, and tag retention rate of each group. And the tagging procedures for the external attachment of hard fin-spines fish were also proposed. The results showed that there were no significant differences in the specific growth rate of fish between groups. Both the survival rates of DD group (96.67%) and DA group (94.44%) were less (but not significant) than C group (97.78%), while the tag retention rate of DA group (100%) was higher (but not significant) than DD group (98.89%). These results demonstrate that drilling on dorsal or anal fin-spines is feasible as an external attachment method of ultrasonic transmitters on Sparidae fishes. In addition, considering the friction between the tagged transmitters and rocks at the bottom of natural waters, which possibly affect the fish behaviors such as swimming, feeding, etc., or lead to tag loss, so drilling on the dorsal fin-spine is preferred for rocky-bottom Sparidae fishes like A. latus as small as 14 cm body length.     

Maximum tag to body size ratios for an endangered coho salmon (<Emphasis Type="Italic">O. kisutch</Emphasis>) stock based on physiology and performance

Many coho salmon stocks (Oncorhynchus kisutch) have been in decline during the past three decades. Canada’s most endangered salmon stock, the Thompson River coho salmon, is being studied extensively as managers attempt to reverse these population declines. Investigators are using acoustic telemetry to track the migratory behaviour and survival of the Thompson River (and other) coho salmon stocks. Coho salmon pre-smolts are relatively small compared with salmonid species that are typically studied using acoustic telemetry; therefore the identification of the appropriate sizes of fish and tags to use is critical. This study tested the effects of surgically implanting the three smallest sizes of acoustic tags currently available on the growth, survival, tag retention, swimming performance and physical condition of coho salmon pre-smolts for 300 days post-surgery. Maximum tag size to body size ratios ranged from 15–17% by fork length and 7–8% by mass for the three tag sizes (11 cm fork length for a 6 × 19 mm tag, 12.5 cm for a 7 × 19 mm tag, and 14 cm for a 9 × 21 mm tag). Based on our results, it is unlikely that coho salmon pre-smolts implanted with acoustic transmitters following these size guidelines would have poor survival in studies of freshwater migratory behaviour as a result of the surgery or the tag.     

Swimming behaviour of upriver migrating sea lamprey assessed by electromyogram telemetry

The main subject of this study was the swimming behaviour of upriver migrating sea lamprey, Petromyzon marinus , with particular focus on identification of their swim strategies to overcome areas of difficult passage. A biotelemetry technique (electromyogram telemetry) was used to register muscle activity of the tagged animals. In the 2005 spawning season, five adult sea lampreys were surgically tagged and released in the field. Before release, electromyogram (EMG) records were calibrated with the P. marinus swimming speed in a swim tunnel. Differences between ground speed and swimming speed in the wild suggest that the calibrated CEMG (coded electromyogram) transmitter output corresponds to an activity index, and cannot be properly related to actual swimming speed. This study notes the need to confirm the laboratory calibration curves, to ascertain their use in determining swimming speed of tagged fish in the wild. In 2006, in order to confirm the field results seven adult sea lampreys were tagged, calibrated in the laboratory and released in a 30-m long experimental outdoor canal. The results were similar: observed swimming speed was generally higher when compared with the swimming speed obtained with the EMG signal. In the river, when swimming through slow-flow stretches, sea lampreys maintained a constant pattern of activity, attaining an average ground speed of 0.76 BL s⁻¹ (2.5 km h⁻¹). When sea lampreys encountered rapid flow reaches they alternated between short movements ( c. 67 s) and periods of rest ( c. 99 s). In each swim bout they progressed approximately 14 m; to overcome more difficult obstacles sea lampreys increased their number of burst movements instead of longer or more violent swimming events. About 43% of the time negotiating difficult passage areas was spent in resting by attaching motionless to the substrate with their oral disk.     

Examination of unidentifiable spined loach individuals found in the overlap zone of two tetraploid species within a single river in Japan

An endangered tetraploid spined loach species, Cobitis takenoi (Cypriniformes: Cobitidae; hereafter called Tango loach) is known to inhabit only a single river in Kyoto Prefecture, Japan. Since Tango loach was discovered recently, in 2010, and only described in 2016, its morphology, ecology, and genetics are not well studied. Another tetraploid spined loach species Cobitis sp. BIWAE type A (hereafter, called Ohshima loach) inhabits the same river. The two loaches are reported as morphologically distinguishable from each other. Although the habitats of the two species in the river are segregated (Ohshima loach and Tango loach inhabit the upper and lower reaches, respectively), they overlap to a small degree in the boundary area. Recently, some individuals with morphological characteristics that are intermediate between the two species were found in the overlap zone. It was suspected that hybrids between the two species were produced since breeding seasons of the two species overlapped. To investigate whether the two species produce hybrids, we performed mitochondrial and nuclear DNA analyses on the unidentifiable individuals. Eight individuals unidentifiable to the species level collected in the river between 2017 and 2018 were examined and compared with the Tango and Ohshima loach species. Using mitochondrial DNA (mtDNA) cytochrome b analysis, we found that six individuals had mtDNA types identical to Tango loach and two individuals had mtDNA types identical to Ohshima loach. Furthermore, sequencing analysis of nuclear recombination activating gene 1 (RAG-1) revealed that each species had species-specific alleles. The phylogenetic analysis indicated that alleles in Tango loach were divided into two clusters and those from Ohshima loach formed a single cluster. There were no discrepancies in the combination between mtDNA and nuclear DNA species types within each specimen. DNA fingerprinting analysis (AFLP) showed that the species-unidentifiable individuals exhibited distinctly segregated genetic groups corresponding with Tango and Ohshima loaches. In summary, no hybrids were detected from among any unidentifiable individual examined in this study. New conventional genetic method for discriminating the two sympatric loach species developed here can be effective tool for the conservation of the Tango loach since there was no strict diagnostic morphological character between them.     

What is “fallback”?: metrics needed to assess telemetry tag effects on anadromous fish behavior

Telemetry has allowed researchers to document the upstream migrations of anadromous fish in freshwater. In many anadromous alosine telemetry studies, researchers use downstream movements (“fallback”) as a behavioral field bioassay for adverse tag effects. However, these downstream movements have not been uniformly reported or interpreted. We quantified movement trajectories of radio-tagged anadromous alewives (Alosa pseudoharengus) in the Ipswich River, Massachusetts (USA) and tested blood chemistry of tagged and untagged fish held 24 h. A diverse repertoire of movements was observed, which could be quantified using (a) direction of initial movements, (b) timing, and (c) characteristics of bouts of coupled upstream and downstream movements (e.g., direction, distance, duration, and speed). Because downstream movements of individual fish were almost always made in combination with upstream movements, these should be examined together. Several of the movement patterns described here could fall under the traditional definition of “fallback” but were not necessarily aberrant. Because superficially similar movements could have quite different interpretations, post-tagging trajectories need more precise definitions. The set of metrics we propose here will help quantify tag effects in the field, and provide the basis for a conceptual framework that helps define the complicated behaviors seen in telemetry studies on alewives and other fish in the field.     

Evaluation of VIE and PIT tagging methods for juvenile cyprinid fishes

Retention and mortality associated with visible implant elastomer (VIE) and passive integrated transponder (PIT) tagged juvenile chub [ Leuciscus cephalus (L.)], dace [ Leuciscus leuciscus (L.)] and roach [ Rutilus rutilus (L.)] were evaluated. PIT tag retention (96.6–100%) was higher than VIE over the 6-month duration of the experiment. VIE retention was significantly better in the head (96.3–98.8%) than in the fins (78.8–90.9%) the first month after tagging, but the opposite was found after 6 months (head = 21.5–57.5%; fins = 77.2–88.8%). Survival was not significantly different from controls for any treatment, except dace tagged with 23-mm PIT (significantly influenced by mass of fish at tagging) and sham PIT tagged dace, because of initial losses. PIT tags are recommended as the most suitable method for tagging individual juvenile chub, dace and roach based on high retention and survival. VIE implantation in the head (studies < 30 days) and fins (studies > 30 days) could provide a cheap, batch-marking alternative, provided retention rates are monitored.     

Spatial and ontogenetic variability in the microhabitat use of stream-dwelling spined loach (Cobitis taenia) and stone loach (Barbatula barbatula)

Ontogenetic and spatial variability in microhabitat use of spined loach Cobitis taenia (Linnaeus), considered as one species for the purposes of this study, and stone loach Barbatula barbatula (Linnaeus) were examined in the River Great Ouse basin, England, using multivariate and habitat suitability methods, including a technique for handling spatial variation in collections of preference curves. Distinct ordinations of spined age classes and stone loach developmental stages, respectively, in canonical correspondence analysis of species × variables × samples relationships suggest that the two species occupy completely different microhabitats; however, young‐of‐the‐year spined loach occurred more often than expected with all developmental stages of stone loach except young larvae. Water velocity and filamentous algae were the most influential microhabitat variables, the latter decreasing in importance with increasing age of both fish species. Preferred water velocities generally decreased with age in spined loach and increased in stone loach, with substratum size generally increasing with fish age in both species. Spatial variation in microhabitat preferences was great in both species but less so in the spined loach, suggesting that limited plasticity in habitat use could account, at least in part, for the latter species’ limited distribution and abundance in the catchment. Preference curves for a species, if generated and verified for all life intervals and all seasons, could be used as a management tool for a given stream or sector of river basin. But preference curves should be generated for each location to ensure that river management decisions with regard habitat and species conservation consider local‐level species requirements. Thus, a multi‐(eco)species and multi‐scale approach is required in habitat suitability assessments.     

鄱阳湖区泥鳅遗传多样性研究

采用同工酶电泳、RAPD引物PCR扩增和线粒体DNA细胞色素b基因全序列3种方法,对鄱阳湖3种斑纹泥鳅的遗传结构进行分析。同工酶电泳显示3种斑纹泥鳅在LDH、MDH和EST这3种同工酶之间存在群体和组织差异;RAPD试验结果显示6条RAPD引物在18尾鄱阳湖泥鳅个体中共扩增出了169条不同分子量的RAPD标记,其中多态性带101条,多态性带的比例为59.56%,平均每个引物产生9.39条带和5.61条多态性带,不同斑纹泥鳅的遗传多样性指数显示3种斑纹泥鳅的遗传水平处于较高水平。以特异性引物进行PCR扩增,获得了1140bp的细胞色素b基因全序列。结果显示,3种不同斑纹泥鳅中检测出了1个共有单倍型和3个特有单倍型。与共有单倍型相比,大花斑泥鳅特有单倍型有91个变异位点,而小花斑泥鳅与无花斑泥鳅特有单倍型的变异位点为20和24个。基于单倍型构建的NJ树和MP树,显示大花斑泥鳅的特有单倍型EU145023处于独立的分支上,这反映出鄱阳湖地区不同斑纹的泥鳅之间在线粒体DNACytb基因中出现了一定距离的分化。       

Circannual vitellogenin levels in Chinese loach <Emphasis Type="Italic">(Misgurnus anguillicaudatus)</Emphasis>

To improve the use of the Chinese loach, Misgurnus anguillicaudatus, as a sentinel species for environmental investigations, normal ranges of plasma vitellogenin (Vtg) was studied. Male and female loaches were collected every 2 months from November 2004 to September 2005, and a specific and sensitive competitive enzyme-linked immunosorbent assay (ELISA) was used to determine plasma Vtg levels. Our data indicated that the average maximum Vtg level of female loaches (757 ± 356 μg mL⁻¹) appeared in March, approximately 1 month before spawning. Female plasma Vtg significantly correlated with gonadosomatic index (GSI) which indicated that female plasma Vtg can be used as an indicator of the reproductive stages of the ovary. Low detectable plasma Vtg levels was detected in a number of male loaches, and the highest average plasma Vtg concentration attained to the level of μg mL⁻¹; after exposure to estrogenic compounds by waterborne, injection or oral food, Vtg can be induced in male fish, so the presence of Vtg in male loaches might be attributed to the ingestion of estrogenic substances in food, the contamination of estrogenic compounds from the living environment, or the estrogen used by the local fish breeders to accelerate the rate of growth during artificial culture. The results indicate that Vtg levels in male and female Chinese loaches will be very helpful in field studies which use Chinese loach as a sentinel species.