Retention of plastic-tipped dart tags in African tigerfish Hydrocynus vittatus

Estimates of tag retention and tagging-related mortality are essential for mark-recapture experiments. Mortality and tag loss were estimated from 15 tigerfish Hydrocynus vittatus marked using Hallmark model PDL plastic-tipped dart tags released into a 1 730 m² pond at Kamutjonga Inland Fisheries Institute, Namibia, and inspected bi-monthly for the presence or absence of tags. No mortality was observed during the experiment. All marked fish had lost their tags after 10 months and 50% tag loss was estimated at 3.9 months. The high tag loss rate indicates that PDL plastic-tipped dart tags are not suitable for long-term studies on this species.     

Effects of double bands on Magellanic Penguins

ABSTRACT Banding penguins is controversial because bands can alter the survival, reproduction, and behavior of marked individuals. The effects of bands are not consistent among band types and, although stainless steel is thought to be better than other materials, tests of the long‐term impact of bands on tag‐loss rates and the reproduction and survival of individuals are needed. We tested three types of external tags on Magellanic Penguins (Spheniscus magellanicus) to measure band effects and tag‐loss rates. In 1993, we double‐tagged 300 penguins with aluminum flipper bands, stainless‐steel flipper bands, or small (2 mm × 10 mm) metal tags attached to foot webbing. We searched for double‐tagged birds for 13 of 15 yrs (1994–2008). Aluminum bands deformed, caused feather wear, injured and killed some penguins, and were lost more often than stainless‐steel bands or web tags. During the first 2 yrs of our study, at least nine penguins lost one aluminum band (N= 71 penguins resighted), but no penguins lost a stainless‐steel band (N= 84) or a web tag (N= 88). During the next 13 yrs, five penguins lost one of their two web tags (N= 89), but none lost a stainless‐steel band (N= 84). Females laid eggs of similar size before they carried a band and in the year following tagging (P= 0.09). The type of tags a female carried did not significantly change egg size (P > 0.22). During the first breeding season after tagging, penguins with aluminum bands had lower reproductive success than penguins with stainless‐steel bands or web‐tags (P= 0.04). The annual survival of females with two stainless‐steel bands was lower (0.79) than that of males with two stainless‐steel bands or males and females with two web‐tags (0.87). Aluminum bands injured Magellanic Penguins, were lost at high rates, and should not be used. Double stainless‐steel bands had no apparent effects on adult male Magellanic Penguins, but reduced survival rates of adult females. A single stainless‐steel band would likely have less impact than two bands, and our results suggest that the impact of a single band would be difficult to measure.     

A Comparison of Floy and Soft VIalpha tags on Hatchery Arctic Charr, with Emphasis on Tag Retention, Growth and Survival

The Floy FTF-69 'fingerling' tag and the soft VIalpha tag are designed to be used on small salmonid fishes (> 100 and > 150mm, respectively). The two tags were compared for 160 days on hatchery-reared Arctic charr, Salvelinus alpinus, (170–209mm). Tag retention and effects on growth rate and survival were analysed. VIalpha-tagged and untagged control fish had similar growth rates and grew significantly faster than Floy-tagged fish during the experiment. Tag retention was significantly higher for Floy tags (94%) than for VIalpha tags (78%). Most VIalpha tag loss (11%) took place within the first 10 days of tagging while there were no Floy tags lost during this period. Survival rates were about equal for all three groups (96–98%), and thus the tags did not seem to affect the survival of charr under hatchery conditions.     

Retention of loop,monel, and passive integrated transponder tags by wild,free‐ranging Lake Sturgeon (Acipenser fulvescens Rafinesque, 1817)

Tagging or marking of fish is instrumental to fisheries biologists and managers seeking to distinguish groups of fish, track movement or migration patterns, and monitor population characteristics. However, tag loss can inhibit the ability of biologists and managers to reach these objectives. The ability of Lake Sturgeon to live for long periods of time and reach large sizes, in combination with their dynamic spawning activity, requires tags to be retained under a variety of environmental and physically demanding conditions. This study evaluated tag retention of loop, monel, and passive integrated transponder (PIT) tags on wild, free‐ranging Lake Sturgeon in Lake Huron and the St. Clair – Detroit River System. Lake Sturgeon in this study were double‐tagged with both a PIT tag under one of the three anterior‐most dorsal scutes and an external tag (loop or monel) at the base of the dorsal fin. Fish were at large for up to 16 years. Overall, tag loss for PIT tags was 1% followed by monel tags at 12% and loop tags at 36%. Tag loss for loop tags was higher when the initial length of Lake Sturgeon tagged was smaller. Tag loss for monel tags increased with time at large but was not related to length at initial tagging. Monel tags left behind abrasion marks when attached to smaller Lake Sturgeon. PIT tag retention was higher than reported in previous studies that tagged other sturgeon species in different body locations. Monel tag retention was higher than other external tag types evaluated in previous studies while loop tags had similar retention rates to external tag types. Most previous studies on tag retention of sturgeon species were of shorter duration and conducted in laboratory settings, therefore loop tags may have performed more favorably during studies under short term laboratory settings. Results of this study suggest that PIT tags inserted below dorsal scutes represent a viable option for long‐term tracking of Lake Sturgeon. Monel tags attached at the base of the dorsal fin also seem to be a viable option relative to other external tag types, but should be limited to larger sturgeon as they can leave behind abrasion marks.     

SURVIVAL RATES FOR THE HAWAIIAN MONK SEAL (MONACHUS SCHAUINSLANDI)

Abstract: Endangered Hawaiian monk seal ( Monachs schauinslandi ) pups at all the major breeding islands in the Northwestern Hawaiian Islands have been tagged since the early 1980s. Pups were double flipper tagged as soon as possible post-weaning. With few exceptions, an extensive tag resighting effort was conducted annually at the same islands. These resighting data were used to estimate seal survival rates from the time of tagging to age one at all locations using the ratio of seals alive in the second year to number of pups tagged. These survival rates among the islands, from weaning to age one, averaged over the years of the study, ranged from 0.80 to 0.90. For young seals over age one, capture-recapture methods were used to calculate survival pooled through several years, and these rates ranged from 0.85 to 0.98. At French Frigate Shoals and Laysan Island, the higher numbers of tagged pups allowed separate estimates of male and female survival to be calculated. These rates suggested that survival of immature females was better than males. Beginning in 1989, survival of immature seals at French Frigate Shoals declined sharply.     

Telemetry tags increase the costs of swimming in northern fur seals,Callorhinus ursinus

Animal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (<1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer‐term impacts on the studied animals.     

Postweaning duration and body composition changes in Southern elephant seal (Mirounga leonina) pups at King George Island.

Weaning mass in southern elephant seals is highly variable, the heaviest pups being three times as heavy as the lightest ones. After weaning, pups undergo an extensive postweaning period in which they draw on their reserves. To quantify the energy expenditure during the postweaning period, changes in mass, body composition, and postweaning duration were measured in southern elephant seals at King George Island, South Shetland Islands, Antarctica. Overall, mean pup weaning mass was 154 +/- 26 kg (n=117) and did not differ between sexes. Mean minimum postweaning duration was 42.5 +/- 7.5 d. Heavier animals at weaning had lower mass-specific mass loss rates than lighter ones, and a faster depletion of body reserves was associated with a shorter postweaning period. The proportion of body mass represented by fat at weaning was 37% +/- 4% (n=47) and did not differ between sexes. Of these pups, 36 were recaptured after a mean period of 36 d after weaning. On average, total mass loss measured in these animals (39 kg) was composed of 39% water, 47% fat, and 12% protein. The composition of mass loss was not significantly different between sexes and was not related to weaning mass or total body energy reserves. However, fatter animals at weaning lost more fat per kilogram lost than thinner ones. Late in the fast, males and females appeared to be in a similar body condition. Nevertheless, the overall proportion of body mass represented by fat at this time was lower than that presented by the same animals at weaning. We estimated that during the postweaning period pups lost, on average, 30% of their mass at weaning. This comprised approximately 35% of the energy and 32% of the fat in the pup's body.     

Improved methods for color‐marking hummingbirds

ABSTRACT Individual color‐marking is an essential tool for studying the behavior of free‐living birds. Hummingbirds represent a particular challenge for traditional avian color‐marking techniques because of their small size and short tarsi. Although several techniques have been successfully used, the retention time of color‐markers and their safety and ease of construction could be improved. I developed two new color‐marking techniques for marking Little Hermits (Phaethornis longuemareus): (1) a plastic back tag constructed by fusing colored beads, and (2) a leg tag attached to a metal band fitted around the tarsus. Both tag designs were visible in field conditions, and neither appeared to adversely affect behavior. Both back and leg tags had high retention rates within seasons, but back tags had a poor retention rate between years. Although these marking techniques were designed for use on one species of hummingbird, they would likely also be useful with other species of hummingbirds.     

Unmarked individuals in mark–recapture studies: Comparisons of marked and unmarked southern elephant seals at Marion Island

The presence of unmarked individuals is common in mark–recapture study populations; however, their origin and significance in terms of population dynamics remain poorly understood. At Marion Island, southern Indian Ocean, where virtually all southern elephant seal Mirounga leonina pups born annually (1983–2008) were marked in a long‐term mark–resight study, large numbers of unmarked seals occur. Unmarked seals originate either from marker (tag) loss or from immigration. We aimed to identify patterns in the occurrence of marked and unmarked individuals that will allude to the possible origin and significance of the untagged component of the population, predicting that tag loss will add untagged seals to mainly adult age categories whereas migrating untagged individuals will be mostly juveniles. We fitted a generalized linear model using the factors month, year and age‐class to explain the relative abundance of untagged seals (tag ratio) from 1997 to 2009. Site usage of untagged seals relative to tagged seals was assessed using a binomial test. Untagged seals, predominantly juveniles, were present in the highest proportions relative to tagged seals during the winter haulout (tagged seals/total seals less than 0.3) and the lowest proportion (approximately 0.5) during the female breeding haulout, increasing in relative abundance from 1997 to 2009. Untagged seals were distributed evenly across suitable haulout sites while tagged seals displayed high local site fidelity and occurred in greater numbers at or near large breeding beaches. Untagged seals are considered to be mostly migrant seals that disperse from other islands within the southern Indian Ocean and haul out at Marion Island during non‐breeding haulouts in particular. Some of these seals immigrate to the breeding population, which can be a key component of the local population dynamics. We emphasize the need for mark–recapture studies to evaluate the role of the unmarked component of a population, thereby inducing a more confident estimation of demographic parameters from the marked sample.     

Semiparametric estimation of tag loss and reporting rates for tag-recovery experiments using exact time-at-liberty data

We present a semiparametric likelihood approach to estimating reporting rates and tag-loss rates from the tags returned from capture-recapture studies. Such studies are commonly used to estimate critical population parameters. Tag loss rates are estimated using double-tagged animals, while reporting rates are estimated using information from high-reward tags. A likelihood function is constructed based on the conditional distribution of the type of tag returned (low or high reward, single or double tag), given that a tag has been returned. This involves many sparse 5 x 1 tag-return contingency tables, and choosing a good functional form for the tag loss rate is difficult with such data. We model tag-loss rates using monotone-smoothing splines, and use these nonparametric estimates to diagnose the parametric form of the tag-loss rate. The nonparametric methods can also be used directly to model tag-loss rates.     

Low Rates of PIT-Tag Loss in an Insectivorous Bat Species

The rate of loss of tags used to mark individuals is an important consideration in wildlife research and monitoring. Passive integrated transponder (PIT) tags (or microchips) generally have high retention rates; however, tag loss rates for small mammals such as insectivorous bats are poorly understood. We double-marked a population of Gould's wattled bats (Chalinolobus gouldii) with forearm bands and PIT tags (with the injection site sealed with surgical adhesive) in January and February 2020 to determine rates of subsequent tag loss over the short- (1–2 months) and medium- (13–14 months) term. Loss of PIT tags occurred in 4 (2.7%) of 146 recaptured individuals, all within 2 months of microchipping. We also recorded 1 occurrence of band loss 11 months after banding. Our study supports assertions that PIT-tag retention rates in small mammals are high, and suggests that rates of tag loss in small bat species are low when surgical adhesive is applied. Quantifying the rate of tag loss enables this variable to be incorporated into mark-recapture models. © 2021 The Wildlife Society.     

Novel Use of PIT Tags in Sea Cucumbers: Promising Results with the Commercial Species Cucumaria frondosa

The lack of a reliable and innocuous mark-recapture method has limited studies that would provide essential information for the management of commercial sea cucumbers. Tagging sea cucumbers is notoriously difficult because of their plastic nature and autolysis capacities. The markers that have so far been tested, mainly on or through the body wall, were either lost rapidly or had major drawbacks (e.g. suitable only for batch identification, requiring complex analysis, causing infections, necrosis, behavioural changes and mortality). The present study explored the efficacy of passive integrated transponder (PIT) tags for individually marking sea cucumbers by assessing retention rates and long-term side effects of tags inserted in previously unstudied tissues/organs. Individuals of the species Cucumaria frondosa were tagged in the body wall, aquapharyngeal bulb and at the base of the oral tentacles. They were monitored closely for evidence of stress, infection, change in feeding and spawning behaviour and tag retention rate. Implanting the tag in an oral tentacle to reach the hydrovascular system of the aquapharyngeal bulb achieved the best retention rates in full-size individuals: from a maximum of 92% after 30 days to 68% at the end of the experimental period (300 days). Efficacy was lower in smaller individuals (84% after 30 d and 42% after 300 d). Following a slight increase in cloacal movements for 15 h post tagging, no side effect was noted in sea cucumbers tagged in the aquapharyngeal bulb via the tentacles. Feeding and spawning behaviours were not affected and no signs of infections or abnormal cell development in the vicinity of the tags were observed. This study indicates that marking sea cucumbers with 8.2 mm long PIT tags implanted via the oral tentacle is an effective technique, yielding relatively high retention rates over long periods without any detectable physiological or behavioural effects.     

REPRODUCTION, SURVIVAL AND TAG LOSS IN CALIFORNIA SEA OTTERS

We observed 40 California sea otters, Enhydra lutris , that were instrumented with implanted radio transmitters and flipper-tagged, and obtained additional data on the reproduction of tagged female otters from the California Department of Fish and Game.
The proportion of instrumented females accompanied by a pup peaked in the spring, with a secondary peak in the fall. Two methods of estimating the annual reproductive rate gave comparable values of 0.90 and 0.94. The average inter-birth interval was 389 d. Two methods of estimating pup survival to weaning gave values of 0.46 and 0.58. Pups either remained with a female less than 80 or more than 120 d. Early mortality of dependent pups appears to be more frequent in California than in Prince William Sound, Alaska.
Two methods of estimation indicated that adult females had the highest survival rates and adult males the lowest. Juvenile females had lower survival rates than adult females but juvenile males had higher survival rates than adult males. The survival rate of juvenile females was lower than that of juvenile males.
The estimated annual loss rate for flipper-tags, based on the instrumented individuals, was 0.26. More individuals lost two tags than would be expected by chance. It is unlikely that accurate estimates of sea otter survival rates can be derived from observations of tagged individuals.     

Weaning mass affects changes in body composition and food intake in harbour seal pups during the first month of independence

In phocid seals, the transition to nutritional independence is abrupt, with females abandoning their offspring after weaning and returning to sea. We hypothesized that body size at weaning may play an important role in the nature of this transition. We studied the changes in body composition and water flux of newly weaning harbour seals over the first 4-6 wk postweaning. Thirty-three pups were dosed with deuterium oxide to estimate total body water (TBW) and a subset of 24 was dosed twice to estimate changes in body composition and water flux. All pups lost body mass over the study period, but TBW increased during the period of mass loss, indicating continued lean tissue growth. Combined data from this and our early study indicated that heavy (>median mass) pups were relatively fatter (41.0% vs. 37.1%) and had significantly greater total body energy at weaning than did light (< or = median mass) pups. Percentage TBW declined linearly over time in light pups but was constant in heavy pups for the first 19 d postweaning and then declined linearly. Both the temporal pattern and composition of mass loss differed between light and heavy pups. Estimated food intake increased in the second 2 wk of study compared to the first 2 wk, in both light and heavy pups, reflecting increased foraging success but at levels still insufficient to meet daily expenditures of most individuals.     

External and internal tags for the green sea urchin

Two internal and three external tags were tested on the green sea urchin. Desirable qualities of a tag were high sea urchin survival, retention for at least a few months, detection on the sea floor by divers, identification of individuals, quick application, and low cost. These objectives were met by an external nylon screw tag visible to divers and two internal aluminum tags detectable with an underwater metal detector. Successful tags were inserted through a hole drilled in the test and were tested in the laboratory and field. All internal tags were retained for the full duration of the 4-month trial and did not retard growth or affect survival. Divers could identify individual urchins with nylon screw tags, but the tag retention rate was lower.     

Suitability of surgically implanted 8-mm passive integrated transponder tags for small-bodied fishes

Innovative tools that benefit conservation are critical as freshwater fishes are lost at unprecedented rates. Mark-recapture methods can characterize population demographics and life-history traits of diverse fishes, but suitable techniques for tagging for individual recognition of small-bodied fishes are rare. Passive integrated transponder (PIT) tag technology may facilitate the tagging of small fishes and early life stages of larger species. However, relatively little research has evaluated the suitability of these small (8.4 × 1.4 mm) tags for many groups of small fishes. Tag loss (retention and survival) and growth of individuals implanted with PIT tags relative to control and sham treatments were compared for eight fishes of differing morphologies. Additionally, the utility of cyanoacrylate to improve tag retention was tested on a subset of taxa. Fish of each species were equally divided and randomly assigned to one of three treatment groups (handled [control], surgical incision [sham], or surgical incision and PIT tag implantation [PIT]). During the 42-d study period, mortalities and expelled tags were counted daily and growth was measured weekly. Researchers can generally expect little tag loss and uncompromised growth rates for a variety of small-bodied fishes; however, initial fish length was related to the magnitude of physiological effects for some taxa (i.e., blacknose dace Rhinichthys atratulus, johnny darter Etheostoma nigrum, juvenile white sucker Catostomus commersonii). Relatively poor survival (<80%) was observed for two benthic species: johnny darter and blacknose dace, often when incision wounds became inflamed before healing. Prevalent tag loss for johnny darter, tadpole madtom Noturus gyrinus, and a dorsal-laterally compressed cyprinid can be reduced by closing the wounds with cyanoacrylate, but with substantially increased mortality rates. This research demonstrates the broad applicability of PIT tagging technology for ecological studies of small-bodied fishes and alleviates many concerns when surgically implanting tags into several fishes.     

Body mass loss of moulting female southern elephant seals,Mirounga leonina,at Macquarie Island

Thirteen female southern elephant seals moulting at Macquarie Island lost an average of 4.46±0.80 kg/day (10.01±1.20g/kg/day). There was no significant difference between this rate of body mass loss and that reported for moulting female southern elephant seals from South Georgia. Moulting female southern elephant seals however exhibited larger mass specific mass loss than either female northern elephant seals or male southern elephant seals, indicating a higher metabolic cost of moult in these animals.     

DIFFERENCES IN FORAGING LOCATION OF MEXICAN AND CALIFORNIA ELEPHANT SEALS: EVIDENCE FROM STABLE ISOTOPES IN PUPS

Female northern elephant seals, Mirounga angustirostris, from Año Nuevo (AN) in central California feed offshore in mid‐latitude waters (40°–55°N). Migratory patterns and foraging locations of seals from Mexico are unknown. Rookeries on San Benitos (SB) islands in Baja California Sur, Mexico, are ～1,170 km south of AN. Although the colonies are similar in size, seals from SB begin breeding earlier and have an earlier breeding birthing peak than seals from AN. To determine if the foraging location of seals from Mexico was similar to that of seals from California, we measured δ¹³C and δ¹⁵N values in the hair of 48 suckling pups at SB and 37 from AN, assuming that their isotopic signatures reflected those of mothers' milk, their exclusive diet. The mean δ¹³C and δ¹⁵N values for SB pups (?16.1‰± 0.9‰ and 17.7‰± 0.9‰, respectively) were significantly higher than those for AN pups (?17.6‰± 0.4‰ and 15.6‰± 1.0‰, respectively). From data on environmental isotope gradients and known behavior of SB and AN populations, we hypothesize that the isotope differences are due to females in the SB colony foraging ～8° south of seals from AN. This hypothesis can be tested by deployment of satellite tags on adult females from the SB colony.     

Grey seal, Halichoerus grypus, energetics: females invest more in male offspring

Grey seal females transfer large amounts of energy to their pups during the brief lactation period. The costs of lactation have been measured using weight changes of mother and pup pairs. Large females come ashore to give birth earlier in the season and lose weight more rapidly than smaller females. The sex ratio of Grey seal pups born is skewed towards males in the early part of the breeding season. Male pups are larger at birth and gain weight more rapidly than female pups, and their mothers show a correspondingly faster rate of weight loss than mothers of female pups. The energy costs of gestation and lactation to a Grey seal mother are 31 GJ for male pups and2–8 GJ for female pups. Males are therefore 10% more costly in energy terms to raise to weaning. Because, on average, large females arrive at breeding sites before smaller animals, biased results on weight changes would be obtained from methods which do not use repeated weighings. We suggest that the high efficiencies of lactation estimated for Harp seals compared with other phocid seals could be accounted for by such a bias.     

Seasonal movements of hooded seals tagged in the Gulf of St. Lawrence,Canada

Hooded seals were tagged as pups (N = 1186) in the Gulf of St. Lawrence between 1975 and 1984. A total of 76 tags have been recovered or resighted. These recoveries indicate a dispersal from the Gulf in the spring to Greenland waters during the summer, and confirm that some seals marked as pups in the Gulf return as adults to this area during the whelping season.