Can ventral pattern be used for individual recognition of the vulnerable Pyrenean brook newt (Calotriton asper)?

Individual recognition of animal species is a prerequisite for capture-mark-recapture (CMR) studies. For amphibians, photoidentification of body pattern is a non-invasive and less expensive alternative than classical marking methods (e.g. passive integrated transponder). However, photo-identification is effective only if the patterns are (i) sufficiently variable between individuals, and (ii) stable over time. This method also depends on the observer’s judgment. In the present study, we assessed the effectiveness of an automatic algorithm (AmphIdent) to recognise ventral colour patterns of the Pyrenean brook newt (Calotrion asper), endemic to the Pyrenees Mountains of France. To assess the performance of the tested method, 113 individuals from two different streams were marked with passive integrated transponders (PIT-tags). We used false rejection rate (FRR), false acceptance rate (FAR) and true acceptance rate (TAR) as metrics to evaluate performances of photoidentification. Mean FRR was 7.3 %, FAR was 5.2 %, and TAR was 92 % across both streams, both sexes and all the observers. FAR was significantly different between sexes, while FRR and TAR were significantly influenced by the interaction between the sex and the stream. Despite these differences, our error rates are among the lowest values found in the literature for both amphibian and non-amphibian computer-assisted photo-identification. We found that poor-quality reference pictures could lead to an increasing difficulty to achieve a correct match when time since first capture rose. Consequently, individual photo-identification using AmphIdent software is a reliable tool to aid in the monitoring the Pyrenean brook newts, provided that pictures are taken with care, reference images are regularly updated and observers are properly trained to use the software and interpret images.

Estimating population parameters for the Critically Endangered Bermuda skink using robust design capture–mark–recapture modelling

Reliably estimating population parameters for highly secretive or rare animals is challenging. We report on the status of the two largest remaining populations of the Critically Endangered Bermuda skink Plestiodon longirostris, using a robust design capture–mark–recapture analysis. Skinks were tagged with passive integrated transponders on two islands and captured on 15 sampling occasions per year over 3 years. The models provided precise estimates of abundance, capture and survival probabilities and temporary emigration. We estimated skink abundance to be 547 ± SE 63.5 on Southampton Island and 277 ± SE 28.4 on Castle Island. The populations do not appear to be stable and fluctuated at both sites over the 3-year period. Although the populations on these two islands appear viable, the Bermuda skink faces population fluctuations and remains threatened by increasing anthropogenic activities, invasive species and habitat loss. We recommend these two populations for continued monitoring and conservation efforts.

A tagging method for very small fish

ABSTRACTThe ability to reliably identify individuals over time and across contexts is essential in numerous areas of science. There are a variety of well-established methods for uniquely marking individuals, such as using paint or dye, visible implant elastomer tags, numbers or barcodes glued to the animal, passive integrated transponders, and more. For some species, life history stages, and/or experiments, however, these existing tagging methods are not sufficient. Here, we describe the method we developed for tagging juveniles of the African cichlid fish, Astatotilapia burtoni, which are too small for the methods used to tag adults. We used fishing line threaded through the needle of an insulin syringe to tie a loop of line through the dorsal muscle of juveniles as small as 10 mm standard length. Unique color patterns on the line can be used to distinguish among individuals. The tag is compatible with normal locomotion and social behavior, discernible to the eye and on camera, durable enough to last at least months, and the juvenile can grow with the tag. For A. burtoni, which is a model system in social neuroscience, the lack of an appropriate tagging method for very small juveniles likely contributes to the relative lack of early-life studies, and the same may be true for other small species. We expect this method to be useful in a variety of species and will facilitate the integration of organismal and behavioral development into more research programs.

Short-Term Mortality and Retention Associated with Tagging Age-0 Walleye Using Passive Integrated Transponders Without Anesthesia

The ability to individually mark juvenile fishes has important implications for fisheries management. For example, marking age-0 Walleye Sander vitreus could provide important information not provided by batch-marking, including individual variation in growth and estimates of length-dependent survival and recruitment. However, the relatively small size of age-0 Walleye in northern temperate lakes has precluded use of many common tagging methods that provide information on individual fish (e.g., various anchor tags, jaw tags). Consequently, we evaluated short-term mortality and retention associated with using 12-mm passive integrated transponders (PITs) to mark age-0 Walleye (total length range = 93–216 mm; mean total length = 157 mm) by conducting 48-h within-lake net-pen trials and 7-d hatchery trials during September–October of 2015 and 2016. We did not anesthetize age-0 Walleye prior to PIT tagging. Our assessment allowed us to determine whether post-tagging mortality and PIT retention varied in relation to implant location (i.e., body cavity or pelvic girdle), fish length, and water temperature. During 2015, mean 48-h mortality rate of age-0 Walleye tagged with PITs in the body cavity was low (mean = 7%; SE = 3%) and did not differ from that of fish marked with only a fin clip (mean = 4%; SE = 2%) and reference fish (mean = 2%; SE = 1%). During 2016, mean mortality rates ranged from 2% (reference fish) to 6% (PIT inserted into pelvic girdle) and did not differ among treatments. During both years, mortality rates for nearly all treatments were highest (> 13%) when water temperatures were ≥ 20°C, but decreased below 5% when water temperatures were ≤ 17°C. During 2016, dead age-0 Walleye in both PIT treatments were smaller than fish that survived. During the 7-d hatchery trials, mean mortality rates were higher for age-0 Walleye with PITs inserted into the body cavity (mean = 13%; SE = 4%) than fish that received a PIT in the pelvic girdle (mean = 4%; SE = 1%) and reference fish (mean = 4%; SE = 2%). Retention of PITs was high (> 96%) during all net-pen and hatchery trials. Collectively, our results suggest that fisheries personnel can use PITs to tag age-0 Walleye without anesthesia with the expectations of high initial retention and low mortality. Mortality rates may be minimized by implanting PITs into the pelvic girdle when water temperatures are ≤ 17°C.

The Entrainment and Screening of Returning and Postspawning Adult Salmonids at Irrigation Canals of the Umatilla River, Oregon

Anadromous salmonids can be vulnerable to entrainment at diversion intake structures on streams, effectively trapping fish in irrigation canals and removing them from a population. Currently little is known about how the differences in timing and direction of movement among adult salmonids contribute to their risk of entrainment and how successful they are at escaping irrigation canals. Potential routes of escape include passing against water currents and through the headgate of an irrigation canal intake or by navigating through screen and bypass infrastructure primarily designed to return juvenile fish to a stream. In this study, passive integrated transponders (PIT tags) were used to track the movement of adult Chinook Salmon Oncorhynchus tshawytscha (n = 573), Coho Salmon Oncorhynchus kisutch (n = 39), and anadromous Rainbow Trout Oncorhynchus mykiss (steelhead, n = 853) as they entered areas of the Umatilla River basin (Oregon) with irrigation canals and as they attempted to escape irrigation canals after entrainment. Although adult steelhead and spring Chinook Salmon often encountered diversions at similar times, the vast majority of entrained adults were steelhead (94%). Between 2% and 8% of adult steelhead observed entering the area were entrained. The entrainment of steelhead was strongly associated with downstream movements and Umatilla River discharge below 40 m3/s. Many downstream-moving steelhead were postspawning fish (kelts). As a result, vulnerability of anadromous adults to entrainment differed by species due to the direction of their movements and how these movements coincide with canal operations and river flows. It is unlikely that the screened irrigation canals acted as an ecological sink; the majority of adult salmonids approached the screen and bypass infrastructure (≥88%) and later river detection confirmed that many had used that infrastructure to return to the river (≥47%). However, half of steelhead appeared to experience bypass delays at fish screens. Adult steelhead that approached the canal headgate after becoming trapped in the canal did not successfully return to the Umatilla River using this route. Unscreened irrigation canals elsewhere may disproportionally trap downstream-moving steelhead, like postspawning kelts, due to their propensity for entrainment and their difficulties escaping through the water intakes of irrigation canals. In streams with anadromous salmonids, fish screen and bypass infrastructure primarily designed to eliminate the permanent entrainment of juvenile fish can also prevent the removal of adult fish that may reproductively contribute to the population.

Bedload transport in a steep alpine stream: Assessment of sediment mobility and virtual velocity using the bedload tracking

The bedload transport is challenging to analyze in field, consequently, several assumptions about it were made basing on laboratory researches or on short-term field studies. During the last decades several monitoring methods were developed to assess the bedload transport in the fluvial systems. The aim of this work is to investigate the transport of the coarse sediment material in a steep alpine stream, using the bedload tracking. The Rio Cordon is a typical alpine channel, located in the northeast of Italy. It is characterized by a rough streambed with a prevalent boulder-cascade and step pool morphology. Since 2011, 250 clasts equipped with Passive Integrated Transponders (PIT) were installed in the main channel, to analyze their mobility along a reach 320 m long. From November 2012 to August 2015, the transport induced by a range of hydraulic forcing between 0.44 m3 s-1 and 2.10 m3 s-1 was assessed by 10 PIT-surveys. First, the mobility expressed by the tracers was analyzed, observing marked differences in terms of travel distance. Then, the average recovery rate achieved during the tracer inventories (Rr > 70%) permitted to define the threshold discharge for each grain size class analyzed and, then, to assess the virtual velocity experienced by the tracers.

The long-term effects and detection ranges of passive integrated transponders in white-clawed crayfish Austropotamobius pallipes

Individual identification of the endangered white-clawed crayfish (Austropotamobius pallipes) can provide valuable information when assessing long-term survival of animals released into the wild; currently the most effective method is the use of passive integrated transponders (PIT) tags. A 360 days ex situ experiment was undertaken on 20-month, captive-born A. pallipes of carapace length (CL): 22–31 mm, to assess growth and survival after PIT-tagging. Thirty crayfish, matched for sex and size, were PIT-tagged, with 30 untagged crayfish as a control. All crayfish survived for the first 60-day post-tagging, indicating that there was no short-term survival effect of the procedure, in controlled conditions. There was no significant difference in survival or growth over the year between tagged and untagged crayfish, indicating that A. pallipes (≥22 mm CL) can be PIT-tagged safely. A second ex situ experiment investigated the detection range of adult, wild-caught, PIT-tagged A. pallipes. Eighteen A. pallipes were tagged with either 8 mm or 12 mm tags and added to different treatments (bare tank, tank with substrate, brick refuge, pipe refuge, pipe refuge plus slate), and the distance to detection was measured. Throughout all treatments the A. pallipes tagged with 12 mm PIT tags were detected significantly further away (35.6 ± 3.8 mm) than the 8 mm PIT-tagged crayfish.

Tagging juvenile European perch (Perca fluviatilis L.) with passive integrated transponders (PIT) – impact on growth, condition, and physiological indexes

The aim of the study was to determine the impact of intramuscular tagging with passive integrated transponders (PIT tags) on the basic condition and hematological and biochemical indexes of the blood plasma of juvenile European perch (initial body weight of approximately 80 g). Throughout the observation period, i.e., for 42 days following PIT implantation, the procedure was not noted to have had a negative impact on fish growth, condition, or feed conversion ratio. The blood plasma biochemical indicators analyzed did not differ statistically significantly between the fish tagged with PIT and the untagged control group. No significant impact from this procedure was noted in the hematological indexes tested. Only with regard to the mean corpuscular hemoglobin (MCH) parameter was the value significantly lower in the fish tagged with PIT than in the control group (P ≤ 0.05). The difference determined was 1.40 pg (28.78 vs. 30.18). The MCH level in the fish tagged with PIT most probably was within the norm for this species. High tag retention (100%) and the lack of any significant impact on condition or hematological and biochemical indexes (with the exception of MCH) permits recommending this tagging method for use in juvenile perch.