Unmarked Fish Research Articles

Development and Evaluation of Methods for Osmotic Induction Marking of Golden Perch Macquaria ambigua with Calcein and Alizarin Red S

AbstractWe conducted a series of osmotic induction procedures for marking golden perch Macquaria ambigua with calcein and alizarin red S (ARS), evaluated the factors that influenced mark quality, and tested for any effects on fish growth and mortality. Three aspects of the marking protocols were considered: immersion time in a 5% salt solution (0, 5, or 10 min), immersion time in the fluorescent dye (5 or 10 min), and concentration of the dye (low or high). Quantitative estimates of mark intensity using photographs of marked fish were made with image analysis software. Although there were some significant interactions between factors, salt immersion was generally the primary determinant of mark intensity, followed by dye concentration and dye immersion time. Fish marked with calcein did not have higher mortality rates than unmarked fish and had significantly higher growth rates. The highest‐exposure ARS treatments resulted in higher mortality and lower growth rates than for unmarked fish. Following this result, a lower‐exposure ARS marking protocol was tested, which resulted in no detectable effects on mortality or growth rates while still producing high‐quality marks. Although further study of the long‐term retention of marks under field conditions is required to understand the limitations of the chemical marking methods examined in this study, our results suggest that the methods would greatly enhance our knowledge of the outcomes of fish stocking.

Dual‐gear approach for calibrating electric fishing capture efficiency and abundance estimates

Abstract Electric fishing depletion systematically underestimates fish abundance in streams. Electric fishing mark‐recapture estimates are unbiased, but only when performed over several days to allow marked fish to recover from electric fishing. A mark‐recapture procedure that can be performed in 1 day and produces unbiased population estimates is described. It involves minnow trapping, marking and releasing juvenile salmonids in a stop‐netted reach, followed by electric fishing the reach 1 h after release of marked fish. Recapture of marked fish during electric fishing can form the basis of a dual‐gear mark‐recapture population estimate, or an unbiased estimate of electric fishing capture efficiency. The marking technique did not affect short‐term catchability of the target species (P = 0.823), and provided unbiased estimates of capture efficiency (0.38–0.40) that were similar to those documented by other researchers. However, local validation to confirm equal catchability of marked and unmarked fish, as described in this study, is recommended.

A video multitracking system for quantification of individual behavior in a large fish shoal: Advantages and limits

The capability of a new multitracking system to track a large number of unmarked fish (up to 100) is evaluated. This system extrapolates a trajectory from each individual and analyzes recorded sequences that are several minutes long. This system is very efficient in statistical individual tracking, where the individual's identity is important for a short period of time in comparison with the duration of the track. Individual identification is typically greater than 99%. Identification is largely efficient (more than 99%) when the fish images do not cross the image of a neighbor fish. When the images of two fish merge (occlusion), we consider that the spot on the screen has a double identity. Consequently, there are no identification errors during occlusions, even though the measurement of the positions of each individual is imprecise. When the images of these two merged fish separate (separation), individual identification errors are more frequent, but their effect is very low in statistical individual tracking. On the other hand, in complete individual tracking, where individual fish identity is important for the entire trajectory, each identification error invalidates the results. In such cases, the experimenter must observe whether the program assigns the correct identification, and, when an error is made, must edit the results. This work is not too costly in time because it is limited to the separation events, accounting for fewer than 0.1% of individual identifications. Consequently, in both statistical and rigorous individual tracking, this system allows the experimenter to gain time by measuring the individual position automatically. It can also analyze the structural and dynamic properties of an animal group with a very large sample, with precision and sampling that are impossible to obtain with manual measures.

Effects of nitrogen gas supersaturation on growth and survival in juvenile Atlantic cod ( Gadus morhua L.)

Gas supersaturation is suggested to be one possible explanation for the extensive mortality that is sometimes experienced during the early life stages in intensive production of cod ( Gadus morhua). In the present study, cod (35 g) were exposed to nitrogen-supersaturated water with first rising levels of total dissolved gas (TDG) for two weeks until the TDG levels reached 103 and 105%, at which the treatment levels were maintained for five weeks. A third group was given vacuum-degassed water (control group, TDG < 100%). Water temperature, TDG, oxygen saturation and other water quality parameters were monitored daily in each tank. Eighty-five out of initially 330 fish in each tank were individually marked with floy tags (biomass was regularly adjusted to 21 kg m 3). Before initiation of treatment and two, four and seven weeks thereafter, all individually marked fish in each tank were measured for total length (TL, cm) and weight ( W, g). The weight of unmarked fish in each tank was measured by bulk weighing. And further, to study stress-related changes in the blood parameters due to supersaturation, a few unmarked fish were randomly sampled from each tank on the same days for blood analysis. Within both treatment groups some fish (1.75%) experienced exophthalmia (“pop eyes”), likely as a chronic effect of gas bubble trauma (GBT). No other effect of exposure to supersaturated water was evident with regard to mortality, growth rate, condition or any of the blood parameters. Juvenile cod are therefore suggested to be relatively tolerant to low to moderate levels of nitrogen gas supersaturated water.

Distinguishing Wild vs. Stocked Lake Trout ( Salvelinus namaycush) in Lake Ontario: Evidence from Carbon and Oxygen Stable Isotope Values of Otoliths

We investigated the potential for using carbon and oxygen isotope values of otolith carbonate as a method to distinguish naturally produced (wild) lake trout (Salvelinus namaycush) from hatchery-reared lake trout in Lake Ontario. We determined δ 13C (CaCO3) and δ 18O (CaCO3) values of otoliths from juvenile fish taken from two hatcheries, and of otoliths from wild yearlings. Clear differences in isotope values were observed between the three groups. Subsequently we examined otoliths from large marked and unmarked fish captured in the lake, determining isotope values for regions of the otolith corresponding to the first year of life. Marked (i.e., stocked) fish showed isotope ratios similar to one of the hatchery groups, whereas unmarked fish, (wild fish or stocked fish that lost the mark) showed isotope ratios similar either to one of the hatchery groups or to the wild group. We interpret these data to suggest that carbon and oxygen isotope values can be used to determine the origin of lake trout in Lake Ontario, if a catalogue of characteristic isotope values from all candidate years and hatcheries is compiled.

Use of genetic tags to identify captive-bred pallid sturgeon (Scaphirhynchus albus) in the wild: improving abundance estimates for an endangered species

The ability to distinguish captive-bred and natural-origin individuals in the wild is critical for evaluating the impact of captive breeding programs on natural populations. Continued persistence of endangered pallid sturgeon (Scaphirhynchus albus) in the Missouri River is largely dependent on captive breeding efforts that spawn natural-origin adults in fish hatcheries and release their progeny into the wild. Prior to release, hatchery-origin individuals are physically marked so they can be distinguished from natural-origin individuals when recaptured. During the years 2004–2006, 24 unmarked juvenile pallid sturgeon tissue samples were collected in the Missouri River downstream of Gavins Point Dam, South Dakota, USA that were presumed natural-origin. However, these individuals were similar in size to hatchery-origin fish released in this area raising concerns that these individuals were actually hatchery-origin fish with lost or malfunctioning tags. We used microsatellite based parentage analysis to determine if the unmarked fish were members of hatchery families that had been released in this area. This retrospective genetic tagging approach revealed that 23 of 24 unmarked fish were indeed hatchery-origin. The origin of the remaining individual remains unknown because genetic samples were not available from all of the families released below the dam and the unassigned fish may have originated from one of these un-sampled families. These results provide important insight into the conservation status of endangered pallid sturgeon as well as provide data important for guiding management decisions. Our results also demonstrate the efficacy of using genetic tags as an alternative or complimentary approach to physically marking individuals.

Comparing the EthoVision 2.3 system and a new computerized multitracking prototype system to measure the swimming behavior in fry fish

Coming from the framework of unmarked fry tracking, we compared the capacities, advantages, and disadvantages of two recent video tracking systems: EthoVision 2.3 and a new prototype of multitracking. The EthoVision system has proved to be impressive for tracking a fry using the detection by gray scaling. Detection by subtraction has given less accurate results. Our video multitracking system is able to detect and track more than 100 unmarked fish by gray scaling technique. It permits an analysis at the group level as well as at the individual level. The multitracking program is able to attribute a number to each fish and to follow each one for the whole duration of the track. Our system permits the analysis of the movement of each individual, even if the trajectories of two fish cross each other. This is possible thanks to t hetheoretical estimation of th e trajectory of each fish, which can becompared with the real trajectory (analysis with feedback). However, the period of the track is limited for our system (about 1 min), whereas EthoVision is able to track for numerous hours. In spite of these limitations, these two systems allow an almost continuous automatic sampling of the movement behaviors during the track.

Age‐Structured Mark–Recapture Analysis: A Virtual‐Population‐Analysis‐Based Model for Analyzing Age‐Structured Capture–Recapture Data

AbstractWe present a new model to estimate capture probabilities, survival, abundance, and recruitment using traditional Jolly–Seber capture–recapture methods within a standard fisheries virtual population analysis framework. This approach compares the numbers of marked and unmarked fish at age captured in each year of sampling with predictions based on estimated vulnerabilities and abundance in a likelihood function. Recruitment to the earliest age at which fish can be tagged is estimated by using a virtual population analysis method to back‐calculate the expected numbers of unmarked fish at risk of capture. By using information from both marked and unmarked animals in a standard fisheries age structure framework, this approach is well suited to the sparse data situations common in long‐term capture–recapture programs with variable sampling effort.

Prevalence and analysis of Renibacterium salmoninarum infection among juvenile Chinook salmon Oncorhynchus tshawytscha in North Puget Sound

Renibacterium salmoninarum causes bacterial kidney disease (BKD), a chronic and sometimes fatal disease of salmon and trout that could lower fitness in populations with high prevalences of infection. Prevalence of R. salmoninarum infection among juvenile Chinook salmon Oncorhynchus tshawytscha inhabiting neritic marine habitats in North Puget Sound, Washington, USA, was assessed in 2002 and 2003. Fish were collected by monthly surface trawl at 32 sites within 4 bays, and kidney infections were detected by a quantitative fluorescent antibody technique (qFAT). The sensitivity of the qFAT was within an order of magnitude of the quantitative real-time PCR (qPCR) sensitivity. Prevalence of infection was classified by fish origin (marked/hatchery vs. unmarked/likely natural spawn), month of capture, capture location and stock origin. The highest percentages of infected fish (63.5 to 63.8%) and the greatest infection severity were observed for fish collected in Bellingham Bay. The lowest percentages were found in Skagit Bay (11.4 to 13.5%); however, there was no difference in prevalence between marked and unmarked fish among the capture locations. The optimal logistic regression model of infection probabilities identified the capture location of Bellingham Bay as the strongest effect, and analysis of coded wire tagged (CWT) fish revealed that prevalence of infection was associated with the capture location and not with the originating stock. These results suggest that infections can occur during the early marine life stages of Chinook salmon that may be due to common reservoirs of infection or horizontal transmission among fish stocks.

A Comparison of the Suitability of Alizarin Red S and Calcein for Inducing a Nonlethally Detectable Mark in Juvenile Guppies

Mark–recapture studies are an important component of fisheries research. A diversity of marks is needed to meet the demands of experimental designs and to overcome species-specific variation in marking success. Suitable marks must not alter the viability of marked individuals, must be easy to detect, and must be retained for an appropriate period of time. I compared the effect of alizarin red S and calcein on the individual growth and mortality rates of guppies Poecilia reticulata via short-term experiments (<14 d) conducted both in environments where alizarin- and calcein-marked fish were allowed to interact with unmarked fish and in environments where fish were segregated by mark. Neither mark affected the growth or mortality of marked individuals. Both marks were easily applied, did not affect the appearance of fish, and could be detected on the skeleton of live, anesthetized fish or ethanol-preserved specimens without the additional preparation (or lethality) involved in detecting marks on otoliths. However, both marks were subject to fading with time and when fish were exposed to high water temperatures or to direct sunlight. Thus, pilot experiments should be conducted under field conditions before marks are used for long-term mark–recapture studies. I also present an inexpensive and portable technique for detecting alizarin that uses a green laser pointer as the excitation source. This alizarin detector performed as well as a portable calcein detector (Leips et al. 2001) and could easily be modified for improved performance. Alizarin red S and calcein fluoresce at different wavelengths, so both marks can be used simultaneously in studies examining multiple treatment groups or cohorts. The use of alizarin red S may be preferred to that of calcein because its red fluorescence is more easily distinguished from the autofluorescence of bone.

A Pipeline Model for Estimating Fishing Mortality in Salmon Mark‐Selective Fisheries

AbstractA model was developed to estimate fishing‐induced mortality and exploitation rates for unmarked salmon Oncorhynchus spp. in mark‐selective fisheries. This model is analogous to a pipeline, and the basic idea is similar to that of the change‐in‐ratio method used for estimating animal abundance. During spawning migration, a unidirectional movement occurs from the ocean to near shore and into freshwater. A series of nonselective and selective fisheries consequently catch these fish on their migration path. The model functions as follows: First, a cohort analysis is completed for the coded‐wire‐tagged fish to obtain their initial abundance and fishery‐specific exploitation rate. Second, fishery‐specific exploitation rates of unmarked fish are derived. Third, the initial abundance of unmarked fish is obtained from the total exploitation rate and escapement and then the ratio between the abundances of unmarked and marked fish is estimated for each fishery. Finally, the fishery‐specific mortality of unmarked fish is estimated. The method assumes that the release mortality rates in selective fisheries are known. Methods for correcting potential bias are suggested. Sensitivity analyses show that the estimated exploitation rates of unmarked fish are less sensitive to bias in the release mortality rate than to bias in the estimated cohort size of marked fish. Bias in release mortality rates results in a diminishing bias of exploitation rates in sequential selective fisheries, but bias in the estimated cohort size results in an increasing bias. An example is given for Sandy River coho salmon O. kisutch in the lower Columbia River. This method does not require double index tagging and can presumably be applied to most fisheries. Some caveats in applying this model to salmon fishery management are given.

USE AND EFFECT OF FREEZE BRANDING ON ROACH (RUTILUS RUTILUS L.)

We tested the effects of freeze branding on growth, survival and mark retention in roach Rutilus rutilus L. (82-268 mm in total length). Markings were applied at two positions on the skin: (1) the depressed area above the anal fin, (2) the muscles above the lateral line and between the caudal and dorsal fins. A control group received no mark. The experiment duration was 30 days, and 120 roach were selected and distributed into three lots. Retention rates were high and ranged between 94% for position 2 and 100% for position 1. Survival rate after 1 month was 87% for freeze branded roach at position 2, 90% for position 1 and 92% for unmarked fish. These differences were not statistically significant. A significant decrease of linear growth was observed for individuals marked at position 2 (3.2 mm.month -1 ), but the implication of the brand itself was unclear. We discuss the short- and long-term properties of freeze branding techniques on roach.

Evaluation of visible implant elastomer for individual marking of small perch and common bully

Visible implant elastomer (VIE) was evaluated as a method for individual marking of small perch Perca fluviatilis and common bully Gobiomorphus cotidianus to use in capture–recapture studies. Growth, survival and mark retention was measured in 25 VIE marked and 15 unmarked fish of each species during a 125 day laboratory experiment. Marking had no effect on growth or survival of either species and mark retention in perch was 100%. Common bully mark retention was high for the initial 30 days but decreased to 72% by the end of the experiment. VIE marking provided an excellent method for individual identification of small perch over periods of at least 125 days, but improvements to common bully mark retention are necessary if VIE is to be used in capture–recapture studies &gt;30 days.

Comparative Effects of Half-Length Coded Wire Tagging and Ventral Fin Removal on Survival and Size of Pink Salmon Fry

Abstract The survival and adult size of pink salmon Oncorhynchus gorbuscha marked as recently emigrating fry with coded wire tags (CWTs) were compared with those of sibling groups that were either unmarked or marked by removing a ventral (pelvic) fin. Prerelease mortality was significantly higher for coded-wire-tagged fish. Survival from fry release to adult return was equal to or less than that of fish with ventral fin clips. Pink salmon marked with CWTs were similar in size at return to pink salmon with ventral fin clips but significantly smaller than unmarked fish. These results indicate that reduced growth after marking contributes to the lower survival reported in other studies of pink salmon marked with CWTs or fin clips. Marking pink salmon as recently emigrating fry with CWTs provides a powerful tool for differentiating between a large number of treatment groups and categories, but doing so will affect survival and size at return and is more detrimental to survival than ventral fin removal.

Efficacy of Minnow Traps for Sampling Mummichogs in Tidal Marshes

We evaluated two types of wire-mesh minnow traps for sampling mummichogs (Fundulus heteroclitus) from intertidal rivulets on the surface of a salt marsh. In field trials, mean catch (no. of fish trap−1) did not differ significantly between trap types nor across soak times ranging from 30 to 240 min. Catch rate (no. of fish trap−1 min−1) was significantly (K-W ANOVA on ranked data, H4df=24.79; p 45 mm TL) of fish were relatively more abundant (Kolmogorov-Smirnov test, p<0.0001) in collections from double-funnel cylindrical traps (volume=10,330 cm3) compared to rectangular traps having about twice the volume and a single funnel cylindrical traps (volume=10,330 cm3) compared to rectangular traps having about twice the volume and a single funnel opening. We estimated entry and escape rates by adding marked fish to traps at initial densities of 30, 60, and 120 trap−1 and measuring changes in the numbers of marked and unmarked fish in each trap type at soak times ranging from 15 to 120 min during the flood stage of the tidal cycle. Escape rate was almost, twice as great from the two-funnel cylindrical traps (0.77 fish min−1) than from the single-funnel rectangular type (0.42 fish min−1) but entry rates did not differ significantly (K-W ANOVA, H4df=0.06; p=0.813) between trap types. Escape rate increased and entry rate decreased as fish density within traps was increased. Escape rates were highest immediately following immersion of the traps, but approached a constant value after 30 min. Trap-specific rates of entry and escape can be affected by a variety of factors including physical characteristics of different trap types, method and timing of trap deployment, and fish behavior. Catch data from minnow traps are unlikely to be useful in measuring relative abundance of mummichogs among habitats unless very short soak times (≤60 min) are used and calibration tests are performed. Use of longer soak times virtually ignores the dynamics involved in determining catch, and is unlikely to provide accurate information on either abundance or size distribution of mummichogs from tidal marsh habitats.

Summer movement and growth of juvenile anadromous salmonids in small western Washington streams

Movements of juvenile coho salmon (Oncorhynchus kisutch), cutthroat trout (Oncorhynchus clarki clarki), and steelhead trout (Oncorhynchus mykiss) were studied by observations and recapture of marked individuals in three western Washington streams to test the hypotheses that few fish would move, downstream movement would predominate, movers would be initially smaller and grow slower after movement than residents, and habitat quality would influence movement. Contrary to predictions, from 28 to 60% of marked fish moved at least one habitat unit, and immigration of unmarked fish also indicated considerable movement. Upstream movement predominated but the stream with the step-pool/cascade channel type had fewer upstream movers and greater distances moved downstream. Coho movers were not smaller than nonmovers, as predicted based on assumptions that movement results from competitive exclusion. Habitat units that coho left were smaller and shallower but lower in density than units where coho remained. Thus, movement is a common phenomenon rather than an aberration, and may reflect habitat choice rather than territorial eviction. Moreover, movers grew faster than nonmovers, so the "mobile fraction" of the population was not composed of competitively inferior fish but rather individuals that thrived. The phenomenon of small-scale habitat- and growth-related movements should be considered when planning and interpreting studies of juvenile salmonid ecology in streams.

Effects of Wood Placement on Movements of Trout and Juvenile Coho Salmon in Natural and Artificial Stream Channels

We monitored the movements of marked juvenile coho salmon Oncorhynchus kisutch, steelhead O. mykiss, and cutthroat trout O. clarki in a stream reach that had been “restored” with placed wood and a reference reach with no wood placement and tracked the growth and movements of individually marked coho salmon among habitats in artificial channels with and without woody debris. Monthly surveys in Shuwah Creek, Washington, indicated that few (0–33%) of the marked trout or coho salmon moved between the restored and reference reaches. However, a rapid decline in both marked and unmarked fish in late fall and the increasing proportion of unmarked fish indicated considerable migration to and from the study reaches. In the artificial channels, fewer fish moved in the simple (with no wood) channel than in the complex (with wood) channel (22% versus 37%), and the mean distance moved was shorter in the complex channel (4.4 versus 6.7 habitat units). In the simple channel, the fish that moved grew faster than those that did not. Movement may facilitate increased growth in stream reaches with little woody debris, and the placement of woody debris may lead to less frequent and shorter movements.

Summer movement and growth of juvenile anadromous salmonids in small western Washington streams

Movements of juvenile coho salmon (Oncorhynchus kisutch), cutthroat trout (Oncorhynchus clarki clarki), and steelhead trout (Oncorhynchus mykiss) were studied by observations and recapture of marked individuals in three western Washington streams to test the hypotheses that few fish would move, downstream movement would predominate, movers would be initially smaller and grow slower after movement than residents, and habitat quality would influence movement. Contrary to predictions, from 28 to 60% of marked fish moved at least one habitat unit, and immigration of unmarked fish also indicated considerable movement. Upstream movement predominated but the stream with the step-pool/cascade channel type had fewer upstream movers and greater distances moved downstream. Coho movers were not smaller than nonmovers, as predicted based on assumptions that movement results from competitive exclusion. Habitat units that coho left were smaller and shallower but lower in density than units where coho remained. Thus, movement is a common phenomenon rather than an aberration, and may reflect habitat choice rather than territorial eviction. Moreover, movers grew faster than nonmovers, so the "mobile fraction" of the population was not composed of competitively inferior fish but rather individuals that thrived. The phenomenon of small-scale habitat- and growth-related movements should be considered when planning and interpreting studies of juvenile salmonid ecology in streams.

Methods for studying spatial behaviour of freshwater fishes in the natural environment

Spatial behaviour of fishes in fresh and brackish water ranges in temporal scales between localized diel movements, often associated with foraging and predator evasion, to seasonal or life‐cycle related events involving movements between freshwater habitats or freshwater and marine biotopes. Recent technological advances have resulted in dramatic improvements in the range of techniques available for the study of spatial behaviour of freshwater fishes in the natural environment, and broadly may be divided into two categories: capture dependent and capture independent. The former incorporates those methods that rely on sampling marked fish (mark–recapture) or unmarked fish (density estimates, catch per unit effort) over defined scales of time and space in order to derive information on distribution and movement. Captured fish may also be tagged with transmitters that radiate energy, enabling the fish to be tracked and/or environmental data to be gathered. Biochemical analysis of samples from fish, requiring non‐destructive sampling (genetic analysis and scale microchemistry) or destructive sampling (otolith microchemistry) may also provide information on migration and ontogenetic processes. Capture independent techniques include visual observation and video techniques, hydroacoustics and automated fish counting. Catch per unit effort and mark–recapture techniques are most efficient where long‐term fishery or monitoring studies are in place and data on crude spatial and temporal scales are acceptable. They also have the advantages of low technical requirements and low equipment costs. Where specific management or ecological questions are pertinent, recapture independent techniques may be more appropriate. Telemetric methods can provide high resolution information at the individual level, while hydroacoustics is increasingly providing information at the population level in large lake and river environments. Biochemical methods are becoming increasingly useful in determining the extent of population segregation, where DNA analysis is used, and in the study of migration and ontogenetic changes in behaviour, where otolith microchemistry and stable isotope analysis is used.

Efficacy of Identifying Stocked Crappies in a Tennessee Reservoir through Oxytetracycline Marking

Oxytetracycline (OTC) immersion was used to identify black-nosed crappies, a morphological variation of black crappie Pomoxis nigromaculatus, stocked into Normandy Reservoir, Tennessee, during fall 1997. The technique effectively marked 97% of the treated fish. Analysis of one otolith per fish by one reader successfully identified 98% of marked and unmarked fish in a blind test. Marks were formed before annulus formation and were not obscured by annulus-related autofluorescence, suggesting that OTC can be effectively used late in the year (Oct and Nov) in Tennessee.