Jeremy Kiszka

Population structure of humpback whales from their breeding grounds in the South Atlantic and Indian oceans

Although humpback whales are among the best-studied of the large whales, population boundaries in the Southern Hemisphere (SH) have remained largely untested. We assess population structure of SH humpback whales using 1,527 samples collected from whales at fourteen sampling sites within the Southwestern and Southeastern Atlantic, the Southwestern Indian Ocean, and Northern Indian Ocean (Breeding Stocks A, B, C and X, respectively). Evaluation of mtDNA population structure and migration rates was carried out under different statistical frameworks. Using all genetic evidence, the results suggest significant degrees of population structure between all ocean basins, with the Southwestern and Northern Indian Ocean most differentiated from each other. Effective migration rates were highest between the Southeastern Atlantic and the Southwestern Indian Ocean, followed by rates within the Southeastern Atlantic, and the lowest between the Southwestern and Northern Indian Ocean. At finer scales, very low gene flow was detected between the two neighbouring sub-regions in the Southeastern Atlantic, compared to high gene flow for whales within the Southwestern Indian Ocean. Our genetic results support the current management designations proposed by the International Whaling Commission of Breeding Stocks A, B, C, and X as four strongly structured populations. The population structure patterns found in this study are likely to have been influenced by a combination of long-term maternally directed fidelity of migratory destinations, along with other ecological and oceanographic features in the region.

Lobomycosis-like disease and other skin conditions in Indo-Pacific bottlenose dolphins Tursiops aduncus from the Indian Ocean

Lobomycosis is a chronic mycotic disease of the skin and subdermal tissues caused by the yeast-like organism Lacazia loboi, which affects humans and Delphinidae. Cases of lobomycosis and lobomycosis-like disease (LLD), a disease very similar to lobomycosis but for which a histological diagnostic is missing, have been reported in small cetaceans from the Americas and Europe. Here we report on LLD in Indo-Pacific bottlenose dolphins Tursiops aduncus from the tropical lagoon of Mayotte, between Mozambique and Madagascar. From July 2004 to June 2008, boat surveys were conducted in Mayotte waters. At least 71 adult dolphins were photo-identified. Six (5 males, 1 female) had multiple raised, greyish nodules on the dorsal fin, head, flanks, belly, back and tailstock that suggested LLD. The lesions were extensive in some cases. The calf of the positive female was also affected. LLD has been present in this community since at least 1999. As sampling was not possible, the aetiology of the disease could not be explored. The emergence of LLD in Mayotte may be related to degradation of the coastal environment associated with rapid urbanization, expanding agriculture and increased release of untreated freshwater runoffs. Other skin lesions included scars, healing wounds, whitish lesions and lumps.

Structure of a toothed cetacean community around a tropical island (Mayotte, Mozambique Channel)

We describe the structure of a toothed cetacean community around the island of Mayotte (South-West Indian Ocean, 45°10′ E, 12°50′ S), using data collected from small boat-based surveys conducted between July 2004 and June 2006. In all, 16 odontocete species were recorded. Diversity (Shannon-Weaver index) was particularly high along the outer slope of the barrier reef. Patterns of spatial distribution underscore the existence of three main cetacean habitat types: the inner lagoon (Indo-Pacific bottlenosed dolphin Tursiops aduncus and humpback dolphin Sousa chinensis), the outer-reef slope (spinner dolphin Stenella longirostris, pantropical spotted dolphin S. attenuate and melon-headed whale Peponocephala electra) and oceanic waters deeper than 500 m (e.g. Blainvilles beaked whale Mesoplodon densirostris). Group characteristics were highly variable among species, with oceanic small delphinids characterised by larger group sizes than strictly coastal and non-delphinid oceanic species. The outer slope of the barrier reef appears to be of primary importance in terms of density and diversity of odontocetes around Mayotte. Results support the hypothesis that a number of cetacean species, particularly several delphinid species, are dependent on coral reef complexes.

Cetacean research in the southern African subregion: a review of previous studies and current knowledge

Cetacean research, in terms of the number of papers, and areas for which data are available, has expanded considerably in the southern African subregion in the past decade, especially in the South-West Indian Ocean. We review cetacean research within this subregion from the 1800s to the present to provide an overview of findings, investigate trends and identify knowledge gaps. Data are presented separately for large whales (those subject to commercial whaling) and smaller cetaceans, and are separated by era and ocean basin. Over 550 peer-reviewed papers and books were identified relating to research on cetaceans within the subregion. More than half (284) have been produced since 1990 and 193 relate specifically to South African waters. The most-studied species are those that are most accessible due to their coastal distributions (southern right whale Eubalaena australis: 45 papers, humpback whale Megaptera novaeangliae: 31 papers, killer whales Orcinus orca: 27 papers, Indo-Pacific bottlenose dolphin Tursiops aduncus: 30 papers, Indo-Pacific humpback dolphin Sousa chinensis (plumbea form): 25 papers) and/or were hunted commercially (sperm whale Physeter macrocephalus: 25 papers). Identified conservation concerns vary throughout the subregion, but include bycatch and directed hunts, oil and gas development, ecotourism activities, shifts in prey resources, and noise and chemical pollution. The inshore stocks of Brydes whales Balaenoptera edeni, the Indo-Pacific humpback dolphin and the Atlantic humpback dolphin S. teuszii were identified as the populations of highest conservation concern, although there are considerable knowledge gaps relating to deep-water species and almost no data (even on species occurrence) are available for several areas and countries.

Preliminary account of cetacean diversity and humpback whale (Megaptera novaeangliae) group characteristics around the Union of the Comoros (Mozambique Channel)

Abstract Cetacean diversity and occurrence has never been investigated in the Union of the Comoros, located in the northern Mozambique Channel. Small boat-based surveys were conducted during the austral winter of 2002, primarily to assess the occurrence of humpback whales (Megaptera novaeangliae) and whether the area represents a wintering ground where the species reproduce. All other cetacean species were also recorded. Opportunistic sighting records were used to provide information on the diversity of cetaceans occurring in the area. Between 2000 and 2003, 12 cetacean species were recorded around the Comoros, including: Megaptera novaeangliae, Stenella longirostris, Peponocephala electra, Stenella attenuata, Tursiops truncatus, Globicephala macrorhynchus, Mesoplodon densirostris, Physeter macrocephalus, Lagenodelphis hosei, Grampus griseus, Mesoplodon pacificus and possibly Tursiops aduncus. During the dedicated surveys, the humpback whale was the most commonly encountered species (72% of sightings) followed by the spinner dolphin (15%). Humpback whale group composition was heterogeneous, but mother-calf pairs were the most commonly sighted (49%). This study demonstrates that the Union of the Comoros is an important site for migrating humpback whales in the southwest Indian Ocean and for a wide variety of toothed cetacean species.

Observations of Longman's Beaked Whale ( Indopacetus pacificus ) in the Western Indian Ocean

Seventeen new sightings, and a total of 32 records, of the little-known Longman’s beaked whale, (Indopacetus pacificus) (also called tropical bottlenose whale or Indo-pacific beaked whale) are reported from the western Indian Ocean. Field identification features are reviewed, and the possibilities of confusion with other beaked whales are noted. Mean group size for the western Indian Ocean sightings was 7.2 individuals (n = 22, SD = 10.9, range = 1 to 40). This is smaller than previously published estimates from the Pacific, reflecting a relatively large number of new sightings of individuals and small groups, which, in turn, reflect the recent description of the external appearance of this species. Recorded dive times were either short (mean = 14 min, range = 11 to 18 min, n = 5) or long (mean = 26 min, range = 20 to 33 min, n = 19). Longman’s beaked whales appear to be widely distributed in the warmer (> 27o C) waters of the western Indian Ocean, but most sightings were over or adjacent to deep slopes (depths 250 to 2,000+ m). Mean sighting rates were much higher in the western Indian Ocean (1 sighting per 31 sea days for visual surveys) and particularly around the Maldives (1 sighting per 21 sea days) than have been reported from the Pacific (1 sighting per 200 sea days). Longman’s beaked whales may therefore be more common in the western Indian Ocean than in the Pacific, although survey methodologies used in the two oceans were not identical. Widespread gillnet fisheries may pose a potential threat to this species in the Indian Ocean.

Mother–embryo isotope (δ15N, δ13C) fractionation and mercury (Hg) transfer in aplacental deep‐sea sharks

Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic values and total mercury (Hg) concentrations were analysed in muscle and liver of mothers and embryos of two aplacental shark species, Squalus megalops and Centrophorus moluccensis. Embryos of the two species had similar or lower isotopic values than their respective mothers, the only exception being for δ¹³C, which was higher in the liver of C. moluccensis embryos than in their mothers. Hg concentrations were systematically lower in embryos compared with their mothers suggesting a low transfer of this element in muscle and liver.

Contrasted accumulation patterns of persistent organic pollutants and mercury in sympatric tropical dolphins from the south-western Indian Ocean

Due to their high trophic position and long life span, small cetaceans are considered as suitable bioindicators to monitor the presence of contaminants in marine ecosystems. Here, we document the contamination with persistent organic pollutants (POPs) and total mercury (T-Hg) of spinner (Stenella longirostris, n =21) and Indo-Pacific bottlenose dolphins (Tursiops aduncus, n=32) sampled from the coastal waters of La Réunion (south-western Indian Ocean). In addition, seven co-occurring teleost fish species were sampled and analyzed as well. Blubber samples from living dolphins and muscle from teleosts were analyzed for polychlorinated biphenyls (PCBs), DDT and metabolites (DDTs), chlordanes (CHLs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and polybrominated diphenyl ethers (PBDEs). Methoxylated PBDEs (MeO-PBDEs), reported as having a natural origin, were also analyzed. T-Hg levels were measured in blubber and skin biopsies of the two dolphin species. Stable isotopes δ(13)C and δ(15)N values were determined in skin of the dolphins and in the muscle of teleosts. For PCBs, HCHs and T-Hg, concentrations were significantly higher in T. aduncus than in S. longirostris. For other POP levels, intra-species variability was high. MeO-PBDEs were the dominant compounds (55% of the total POPs) in S. longirostris, while PCBs dominated (50% contribution) in T. aduncus. Other contaminants showed similar profiles between the two species. Given the different patterns of POPs and T-Hg contamination and the δ(15)N values observed among analyzed teleosts, dietary and foraging habitat preferences most likely explain the contrasted contaminant profiles observed in the two dolphin species. Levels of each class of contaminants were significantly higher in males than females. Despite their spatial and temporal overlap in the waters of La Réunion, S. longirostris and T. aduncus are differently exposed to contaminant accumulation.

What drives island-associated tropical dolphins to form mixed-species associations in the southwest Indian Ocean?

Abstract Mixed-species associations are temporary aggregations of individuals of different species involved in similar activities. Such associations form for foraging, protection against predators, and social advantage. Mixed-species groups in delphinids are frequent in the wild. We aimed to understand the ecological significance of mixed-species group formation by 2 tropical delphinids, the spinner dolphin (Stenella longirostris) and the pantropical spotted dolphin (Stenella attenuata), in waters surrounding the island of Mayotte in the southwestern Indian Ocean. We used sighting data collected year-round from 2004 to 2009. We encountered a total of 67 mixed-species groups (comprising 21% of all groups observed) of spinner and pantropical spotted dolphins around Mayotte. No daily or seasonal variability in the occurrence of associations was detected. Behavioral activities of single- and mixed-species groups differed significantly. Foraging was observed only in single-species groups of pantropical spotted dolphins. Mixed-species groups were larger than single-species groups. When in association, spinner dolphins used deeper waters than while in single-species groups. No evidence of association for social advantage was observed. We suggest that spinner dolphins associate with spotted dolphins for protection against predators when transiting between resting areas.

Epidemiology of lobomycosis-like disease in bottlenose dolphins Tursiops spp. from South America and southern Africa

We report on the epidemiology of lobomycosis-like disease (LLD), a cutaneous disorder evoking lobomycosis, in 658 common bottlenose dolphins Tursiops truncatus from South America and 94 Indo-Pacific bottlenose dolphins T. aduncus from southern Africa. Photographs and stranding records of 387 inshore residents, 60 inshore non-residents and 305 specimens of undetermined origin (inshore and offshore) were examined for the presence of LLD lesions from 2004 to 2015. Seventeen residents, 3 non-residents and 1 inshore dolphin of unknown residence status were positive. LLD lesions appeared as single or multiple, light grey to whitish nodules and plaques that may ulcerate and increase in size over time. Among resident dolphins, prevalence varied significantly among 4 communities, being low in Posorja (2.35%, n = 85), Ecuador, and high in Salinas, Ecuador (16.7%, n = 18), and Laguna, Brazil (14.3%, n = 42). LLD prevalence increased in 36 T. truncatus from Laguna from 5.6% in 2007-2009 to 13.9% in 2013-2014, albeit not significantly. The disease has persisted for years in dolphins from Mayotte, Laguna, Salinas, the Sanquianga National Park and Bahía Málaga (Colombia) but vanished from the Tramandaí Estuary and the Mampituba River (Brazil). The geographical range of LLD has expanded in Brazil, South Africa and Ecuador, in areas that have been regularly surveyed for 10 to 35 yr. Two of the 21 LLD-affected dolphins were found dead with extensive lesions in southern Brazil, and 2 others disappeared, and presumably died, in Ecuador. These observations stress the need for targeted epidemiological, histological and molecular studies of LLD in dolphins, especially in the Southern Hemisphere.