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Following centuries of exploitation, basking sharks (Cetorhinus maximus) are considered by IUCN as Endangered in the Northeast Atlantic, where they have now been substantially protected for over two decades. However, the present size of this population remains unknown. We investigated the use of photo-identification of individuals’ dorsal fins, combined with mark-recapture methodology, to investigate the size of populations of basking shark within the west coast of Scotland. From a total of 921 encounters photographed between 2004 and 2011, 710 sharks were found to be individually identifiable based on dorsal fin damage and natural features. Of these, only 41 individuals were re-sighted, most commonly both within days of, and close to the site of, the initial encounter. A smaller number were re-sighted after longer periods of up to two years. A comparison of the distinguishing features of individuals on first recording and subsequent re-sighting showed that in almost all cases these features remained little changed, suggesting the low re-sighting rate was not due to a loss of distinguishing features. Because of the low number of re-sighting we were not able to produce reliable estimates for the long-term regional population. However, for one 50 km diameter study area between the islands of Mull, Coll and Tiree, we were able to generate closed-population estimates for 6–9 day periods in 2010 of 985 (95% CI = 494–1683), and in 2011 of 201 (95% CI = 143–340). For the same 2011 period an open-population model generated a similar estimate of 213 (95% CI = 111–317). Otherwise the low rate and temporal patterning of re-sightings support the view that such local basking shark populations are temporary, dynamic groupings of individuals drawn from a much larger regional population than previously supposed. The study demonstrated the feasibility and limitations of photo-identification as a non-invasive technique for identifying individual basking sharks. [ABSTRACT FROM AUTHOR]

We estimated sex- and age-specific apparent survival of harbor seals (Phoca vitulina richardii) born at Tugidak Island, Alaska, from 2000 to 2007 using mark-recapture models and photographs of ventral pelage markings to identify individuals. Estimates of annual apparent survival (1 - (mortality + emigration)) of females were from 0.05 to 0.10 higher than those of males and were 0.820 for weaning (~1 month) to 1 year, 0.865 for 1-3 years, and 0.929 at 3-7 years. Annual survival of males was 0.717, 0.782, and 0.879 for the same ages. Highest mortality occurred preweaning, with cumulative mortality to 4 weeks of age of 0.259, indicating this is the most vulnerable period for Tugidak harbor seals. Estimates of survival, not biased by misidentification, required that an individual had at least 2 good-quality, matching photographs in the photograph library. The number of photographs available for matching improved resighting probabilities from 0.43 for seals with 2 photographs to 0.69 for seals with 8 photographs, but this heterogeneity did not affect survival estimates. Survival estimates based on photograph-identification data were nearly identical to those based on resightings of flipper-tagged seals using mark-recapture models with a preliminary double-tag-loss estimate of 2.5% per year. Photograph identification of natural pelage markings provides a viable method for estimating vital rates of harbor seals even at large haul-outs (> 1,000 animals) and may be useful for populations of conservation concern that require low disturbance of animals or where capturing sufficient numbers of seals for artificial marking is not feasible. [ABSTRACT FROM AUTHOR]

The article presents a study which presents population estimates of Irrawaddy dolphins, Orcaella brevirostris, in Chilika Lagoon, India obtained from photo-identification based mark-recapture methods. The study used a Canon digital camera and open and closed population models to estimate the population of Irrawaddy dolphins in the region. Results show that mark-recapture methodology has provided significant information on Irrawaddy dolphins.

The article presents a study which investigated the size of a closed population of bowhead whales in the Bering-Chukchi-Beaufort seas using photo-identification data and Empirical Bayes capture-recapture analysis. The authors estimated the capture probabilities and the abundance of the mammals for populations including unmarked individuals. It is stated that Empirical Bayes approach resulted in smaller or comparable biases for the estimated values of the population compared to the biases observed using the beta prior.

Knowledge of the local and migratory movements of humpback whales (Megaptera novaeangliae) from New Caledonia is very limited. To investigate this topic, we attached satellite-monitored tags to 12 whales off southern New Caledonia. Tag longevity ranged from 1 to 52 days (&#x00AI; = 22.5 days). Tagged whales generally moved to the south or southeast, with several spending time in a previously unknown seamount habitat named Antigonia before resuming movement, generally toward Norfolk Island or New Zealand. However, 1 female with a calf traveled the entire length of the western coast of New Caledonia (~450 km) and then west in the direction of the Chesterfield Reefs, a 19th century American ("Yankee") whaling ground. None of the New Caledonia whales traveled to or toward eastern Australia, which is broadly consistent with the low rate of interchange observed from photo-identification comparisons between these 2 areas. The connections between New Caledonia and New Zealand, together with the relatively low numbers of whales seen in these places generally, support the idea that whales from these 2 areas constitute a single population that remains small and unrecovered. [ABSTRACT FROM AUTHOR]

Bottlenose dolphins (Tursiops truncatus) are consistently observed in the Marlborough Sounds, New Zealand. However, prior to the present study, no research has previously focused on this species within these waters, despite the potential for human impacts. Photo-identification undertaken during boat-based surveys conducted between 2003 and 2005 were used to assess occurrence, abundance, and movement patterns of bottlenose dolphins in the Marlborough Sounds. Longterm site fidelity was evident, with the majority of individuals resighted over multiple years. Lagged identification rates showed consistency over a 4-y period, with some individuals remaining for longer periods, while others frequently interchanged between different areas of the Marlborough Sounds. Migration rates were high, with approximately 25% leaving and entering the 890 km² region annually. Bottlenose dolphins in the Marlborough Sounds appear to form part of a larger, open, coastal population consisting of 385 individuals, with 211 (95% CI = 195 to 232) dolphins utilizing the region per annum. While their occurrence within these waters is frequent, the Marlborough Sounds appear to be only a section of a much larger home range for this bottlenose dolphin population. [ABSTRACT FROM AUTHOR]

The article presents a study which analyzes the survival and abundance of bottlenose dolphin Tursiops truncatus with the use of a photo-identification data gathered from 1999-2004 on the two islands of Azores archipelago. It states that capture-recapture models are developed to increase the knowledge of demographic parameters and to address the problems related to sampling open populations of diversified animals. It mentions the use of open models and Pollock's robust design to approximate population size, survival possibility and the rates of emigration. Results show that adult survival is higher than the sub-adults with higher possibility of emigration.

Identifying individuals through time can provide information on population size, composition, survival and growth rates. Identification using photographs of distinctive physical characteristics has been used in many species to replace conventional marker tagging. We evaluated photographic records over 7 years of Vulnerable whale sharks Rhincodon typus, at an aggregation in the Seychelles, for estimation of population size and structure. We collected 11,681 photographs of which only 1,149 were suitable for comparison using semi-automated matching software (I³S) of individual spot patterns behind the gills. Photo-identification showed that there was considerable loss of marker tags and enabled an estimation of the rate of tag loss. The combination of photo-identification with marker tagging identified a total of 512 individual sharks over 2001-2007. Of these, therewere 115 resightings in subsequent years with two sharks identified in 2001 resighted 5 years later in 2006 and another shark sighted in 2001 resighted in 2007. Estimates of abundance using conventional open mark-recapture models for 2004-2007 were 348-488 sharks (95% confidence interval), with a high level of entry into the population by itinerants. Annual apparent survival probability was 0.343- 0.781 over 2004-2007, with an average annual recapture probability of 0.201. These results are the first to suggest a highly transient population of whale sharks around the Seychelles, indicating that international or at least regionalscale conservation approaches are required. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the movements of southern right whales (Eubalaena australis) between Australian and subantarctic New Zealand populations. Photo-identifications from Australian and subantarctic New Zealand ranges were compared. Three between-population movements, including two instances of females calving in each of two population-specific calving grounds were found. Limited movement is suggested by genetic evidence from analysis of mitochondrial DNA (mtDNA) sequences and haplotype frequencies.

Passive acoustic data are increasingly being used as a tool for helping to define marine mammal populations and stocks. Fin whale (Balaenoptera physalus) songs present a unique opportunity to determine interstock differences. Their highly stereotyped interpulse interval has been shown to vary between geographic areas and to remain stable over time in some areas. In this study the structure of songs recorded at two geographically close feeding aggregations in the Gulf of St. Lawrence (GSL) and Gulf of Maine (GoM) was compared. Recordings were made from September 2005 through February 2006 in the GSL and intermittently between January 2006 and September 2007 at two locations in the GoM. 6257 pulse intervals corresponding to 19 GSL and 29 GoM songs were measured to characterize songs from both areas. Classification trees showed that GSL songs differ significantly from those in the GoM. The results are consistent with those derived from other stock structure assessment methodologies, such as chemical signature and photoidentification analysis, suggesting that fin whales in these areas may form separate management stocks. Song structure analysis could therefore provide a useful and cost-efficient tool for defining conservation units over temporal and geographical scales relevant to management objectives in fin whales. [ABSTRACT FROM AUTHOR]

Western gray whales ( Eschrichtius robustus) are critically endangered and anthropogenic threats, such as entanglement in fishing gear and collisions with vessels, may be acting to limit recovery of the population. Thus, examining the magnitude of such anthropogenic interactions using a scar-based approach is warranted. A multi-year (1995–2005) photo-identification study of western gray whales on their feeding ground off northeastern Sakhalin Island, Russia, has resulted in a large data set of digital and film images of 150 individuals. These images were reviewed and scored for anthropogenic scarring by recording the presence of visible scars resulting from fishing gear entanglement and vessel collisions in 21 defined body regions. In total, 20.0% ( n= 30) of whales identified during the study period had detectable anthropogenic scarring, with 18.7% ( n= 28) determined to have been previously entangled in fishing gear at least once and 2.0% ( n= 3) to have survived at least one vessel collision. These estimates are likely to be conservative given the nature of the photo-identification data set, but indicate that male and female western gray whales are subject to anthropogenic interactions. Future studies designed to systematically estimate the frequency and rates of anthropogenic events are needed and would have direct conservation and management implications. [ABSTRACT FROM AUTHOR]

The article presents a preliminary photo-identification study on the bottlenose dolphin or Tursiops trunactus in Hauraki Gulf, New Zealand. Researchers analysed photographs of individual bottlenose dolphins taken in Hauraki Gulf between 2000 and 2003. The analysis resulted in 162 uniquely identifiable individuals being included in the gulf's bottlenose dolphin photo-identification catalogue. It sighted seventy percent of those catalogued dolphins more than once, with sighting frequency ranging from one to eleven encounters. Comparison of individual photo-identification catalogues between Bay Islands and Hauraki indicated 59% of the individuals catalogued in Hauraki Gulf being confirmed as occupying in both locations.

The article presents a study on abundance and demography of bottlenose dolphins or Tursiops truncatus in Dusky Sound, New Zealand. Researchers estimated that there were 102 bottlenose dolphins in Dusky Sound during the summer of 2007/2008 by conducting a photo-identification census and capture-recapture analyses. Sexes of 79 individuals, of which 98-99% are adults and sub-adults, in Dusky Sound were predicted by employing the use of a sex-prediction model derived from laser-metric photographs of dolphins in Doubtful Sound.

Photo-identification surveys conducted between 2002 and 2005 were used to determine dolphin home ranges and site fidelity within the Indian River Lagoon (IRL), Florida. The IRL was divided into six segments based on hydrodynamics and geographic features for purposes of characterization. Among the 615 dolphins with identifiable dorsal fins, 339 had ≥6 sightings and were used in segment and linear range analyses. The majority (98%) of dolphins were seen in ≤3 consecutive segments (331/339); of these, 44% (144/331) occurred in two segments, and 33% (109/331) in one segment. No dolphins were observed in all six segments. The largest number of dolphins was sighted in segment 1C (North Indian River). However, the highest density of dolphins was found in segment 2 (North-Central Indian River). Re-sighting rates for dolphins with ≥6 sightings ranged from 2.8 to 8.7 times observed. The mean linear home range varied from 22 to 54 km. Distributional analyses indicated that at least three different dolphin communities exist within the IRL: Mosquito Lagoon, and the North and South Indian River. No statistically significant correlations were found between the total number or density per km2 of dolphins and surface water area, salinity, or contaminant loads within segments of the lagoon. These results suggest that dolphins do not selectively avoid areas with relatively unfavorable water quality. IRL dolphins should be studied on smaller spatial scales than currently practiced, and potential anthropogenic impacts should be evaluated based on geographic partitioning. [ABSTRACT FROM AUTHOR]

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