Estimating the abundance of long-lived, migratory animals is challenging but essential for managing populations. We provide the first abundance estimates of endangered humpback whales Megaptera novaeangliae from their breeding grounds in Oceania, South Pacific. Using fluke photo-identification (1999−2004, n = 660 individuals) and microsatellite genotypes (1999−2005, n = 840 individuals), we estimated abundance with open capture-recapture statistical models. Total Oceania abundance and trends were estimated from 4 primary and 5 secondary sampling sites across the region. Sex-specific genotype data enabled us to account for the difference in capturability of males and females, by doubling male-specific estimates of abundance derived from genotypes. Abundance estimates were congruent between primary-and secondaryregion data sets, suggesting that the primary regions are representative of all Oceania. The best estimate of total abundance was 4329 whales (3345−5313) in 2005, from a sex-specific POPAN super-population model, which includes resident whales and those migrating through the surveyed areas. A doubled-male POPAN abundance estimate from 2003 (n = 2941, 95% CI = 1648−4234) was considered the most plausible for the 4 primary survey areas and was similar to the 2003 doubled-male estimate derived from Pradel capture probabilities (n = 2952, 95% CI = 2043−4325). Our results confirm that Oceania is the least abundant humpback whale breeding population in the southern hemisphere. Pradel models showed no significant trend in abundance, which contradicts the recovery seen in most other populations throughout the world. Thus we suggest that the whales in this area warrant continued study and management attention.KEY WORDS: Megaptera novaeangliae · South Pacific · Capture-recapture · Genotyping · Endangered speciesResale or republication not permitted without written consent of the publisher

Understanding the organization and dynamics of social groups of marine mammals through the study of kin relationships is particularly challenging . Here, we studied a stable social group of sperm whales off Mauritius, using underwater observations, individual-specific identification, non-invasive sampling and genetic analyses based on mitochondrial sequencing and microsatellite profiling. Twenty-four sperm whales were sampled between 2017 and 2019. All individuals except one adult female shared the same mitochondrial DNA (mtDNA) haplotype—one that is rare in the western Indian Ocean—thus confirming with near certainty the matrilineality of the group. All probable first- and second-degree kin relationships were depicted in the sperm whale social group: 13 first-degree and 27 second-degree relationships were identified. Notably, we highlight the likely case of an unrelated female having been integrated into a social unit, in that she presented a distinct mtDNA haplotype and no close relationships with any members of the group. Investigating the possible matrilineality of sperm whale cultural units (i.e. vocal clans) is the next step in our research programme to elucidate and better apprehend the complex organization of sperm whale social groups.

After decades of whaling, Oceania humpback whales Megaptera novaeangliae have such a low rate of recovery that a trend is not currently measurable. They are listed as Endangered by the IUCN, and any possible threat to the whales needs to be carefully monitored and mitigated. Whale-watching activities represent an important economic development throughout the South Pacific but also carry a potential risk of impact for these recovering populations. New Caledonia is among the leading countries for humpback whale watching in Oceania. Land-based theodolite observations were conducted between 2005 and 2007 to assess the effect of boats on humpback whale behaviour in New Caledonia. Natural experiments were used to investigate the response of whales to boat approaches, and opportunistic observations were used to assess which variables best described variability in behaviour. Over 80% of whales approached by boats significantly changed their behaviour. Changes in path predictability (directness and deviation index) were most commonly affected and are likely to represent an efficient and low-cost avoidance strategy. Linear models showed that as boats get closer, humpback whales significantly increased the sinuosity of their path. The threshold for such a response corresponded to an approach distance of 335 m. Based on these results and considering the vulnerability of the humpback whale population in New Caledonia, we suggest reinforcing management measures to increase the likelihood that the whale-watching industry is sustainable.

Summary 1.Mark-recapture studies are often used to estimate population size based on a single source of individual identification data such as natural markings or artificial tags. However, with the development of molecular ecology, multiple sources of identification can be obtained for some species and combining them to obtain population size estimates would certainly provide better information about abundance than each survey can provide alone. 2. We propose an extension of the Jolly-Seber model to infer abundance by combining two sources of capture-recapture data. The need to merge both sources of data was motivated by studies of humpback whales in which both photo-identification and DNA from skin biopsy samples are often collected. As whales are not necessarily available by both sampling methods on any given occasion, they can appear twice in the combined data set if no combined sampling ever occurred during the survey, i.e. being photographed and genotyped on the same occasion. Our model thus combines the two sources of information by estimating the possible overlap. Monte Carlo simulations are used to assess the properties of the present estimator that is then used to estimate the size of the humpback whale population in New Caledonia. The new openpopulation estimator is also compared with classic closed-population estimators incorporating either temporal and ⁄ or individual heterogeneity in the capture probability: the purpose was to evaluate which approach (closed or open population) was the least biased for an open population with individual heterogeneous capture probabilities. 3. When all assumptions are met, the estimator is unbiased as long as the probability of being double-tagged (e.g. photographed and biopsied on the same occasion) on every occasion is above 0AE2. 4. The humpback whale case study in New Caledonia shows that our two-source Jolly-Seber (TSJS) estimator could be more efficient in estimating population size than models based only on one type of data. For monitoring purposes, the proposed method provides an efficient alternative to the existing approaches and a productive direction for future work to deal with multiple sources of data to estimate abundance. 5. R-codes formatting the data and implementing the TSJS model are provided in Resource S5.

The coastal waters of Baja California Sur, Mexico, include some of the most important foraging grounds of the East Pacific green turtle Chelonia mydas. However, they are also important fishing grounds for artisanal fleets, leading potentially to high levels of bycatch mortality. We studied the impact of a small-scale gill-net fishery at San Ignacio lagoon, north-west Mexico, an important green turtle feeding ground. We conducted mortality censuses and interviewed local fishers to estimate total bycatch mortality at the lagoon. We also used marked drifters and carcasses to estimate stranding probabilities of turtles taken as bycatch. During 2006-2009 we found 262 dead turtles; 96% of the mortality occurred in May-August corresponding to the fishing season for halibut Paralichthys californicus and guitar-fish (Rhinobatus sp.). Stranding probability estimated from drifters was 0.062 (95% confidence interval, CI, 0.035-0.094), yielding a minimum mortality of 3,516 turtles during 2006-2008 (95% CI 2,364-6,057) or 1,172 animals per year. This is probably an underestimate of real mortality as the drifters have higher stranding probabilities than carcasses and most of the nets were set in the lower lagoon where carcasses rarely strand. Interviews with local fishers yielded a similar estimate of 1,087 (95% CI 901-1,286) dead turtles per year. This study is emblematic of the impact of artisanal fleets on marine turtles caused by overlap of fishing and turtle feeding areas. In 2009 strandings declined by . 97%, resulting from a change in fishing practices because of increased vigilance by enforcement authorities, underscoring the importance of law enforcement to protect threatened species.