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The increase and diversification of vessel traffic worldwide has resulted in a variety of known disturbances to dolphins. As a remote island chain, the Hawaiian Islands rely heavily on the marine environment for transportation, recreation, and fishing that aggregates into significant levels of vessel traffic. Given the known presence of dolphins in this region, there is a gap in knowledge regarding the relative exposure risk that vessel traffic poses to island-associated dolphin populations in Hawai'i. This research identified the spatial distribution of pantropical spotted dolphins (Stenella attenuata) and common bottlenose dolphins (Tursiops trun-catus) and determined the extent of their overlap with various categories of vessel traffic in Maui Nui, Hawai'i. Species distribution was determined using kernel density estimates based on sighting data from 50 spotted dolphin sightings and 75 bottlenose dolphin sightings collected from 2013 to 2018. A combination of vessel GPS and Automatic Identification Systems (AIS) vessel tracks were used to quantify vessel traffic within the study area, resulting in 22,464 vessel tracks that were subsequently compiled into categories for analysis from 2014 to 2017. Risk of vessel exposure between vessels and dolphins, or co-occurrence, was determined by calculating the product of predicted dolphin density and predicted vessel density. Both species were exposed to vessel traffic risk over 100% of their distribution, but their highest exposure risk varied spatially, with high risk defined as > 0.25 on a normalized scale of low (0) to high (1) risk. The highest vessel exposure risk for spotted dolphins occurred in deeper, offshore waters, while the highest risk for bottlenose dolphins was in shallow, coastal waters. The vessel categories with the largest area of high risk to spotted dolphins were tour vessel and commercial fishing vessel traffic, while commercial transportation traffic had the highest exposure risk for bottlenose dolphins. This article provides baseline information for understanding the vulnerability of two island-associated dolphin populations to the threat of vessel traffic and highlights the differences in relative exposure risk based on species and vessel categories. [ABSTRACT FROM AUTHOR]

In Maui Nui, Hawai'i, limited information is available regarding the impact of fisheries interactions on two island-associated populations of common bottlenose (Tursiops truncatus) and pantropical spotted (Stenella attenuata) dolphins. To quantify the number of individuals with evidence of fisheries interactions, this study examined images of bottlenose and spotted dolphins' dorsal fins, mouthlines, and bodies that were photographically identified during survey efforts from 1996 to 2020. Our results reveal that 27% of the 255 identified bottlenose dolphins and 13% of the 374 identified spotted dolphins displayed one or more fishery gear-related scars. These data suggest that fisheries interactions may pose a serious threat to the population of bottlenose dolphins and is a concern for spotted dolphins in Maui Nui, Hawai'i. Our methodology of reviewing above- and underwater footage for mouthline and body images increased scar-detection rates by 51 and 40% for bottlenose and spotted dolphins, respectively. We recommend that future surveys expand dorsal fin photo-identification efforts to collect additional above- and underwater images of animals' mouthlines and bodies when in the field. In conjunction with the apparent decline in the Maui Nui bottlenose dolphin population, our findings highlight the need for further investigation regarding the level of impact fisheries interactions have on the status of these populations. [ABSTRACT FROM AUTHOR]

Very little is known about the foraging ecology of killer whales (Orcinus orca) in tropical oceans and on how these large apex predators affect prey communities. In most tropical waters, the presence of killer whales is unpredictable, and most information on their ecology is inferred from opportunistic records. This is particularly the case in the Indian Ocean where limited information is available. Between 2002 and 2017, killer whales were opportunistically encountered around the Mozambique Channel island of Mayotte in the eastern Comoros Archipelago (southwest Indian Ocean). A total of 15 killer whale sightings collected by various local experts were compiled and used to describe observed feeding events. Twenty-seven distinct individuals from four separate groups were identified by photo-identification, highlighting short-term site fidelity (minimum 7 days) to this area. Feeding was observed on seven occasions, and recorded prey included two species of elasmobranchs (Centroscymnus coelolepi and Mobula spp.) and two species of cetaceans: a humpback whale (Megaptera novaeangliae) calf and a pantropical spotted dolphin (Stenella attenuata). This study represents the first account of killer whales foraging on a combination of marine mammals and elasmobranchs in tropical waters, and describes the first presumed predation on a humpback whale calf in the southwest Indian Ocean. [ABSTRACT FROM AUTHOR]

We examined the incidence of bent or collapsed dorsal fins of eight species of odontocetes observed in the nearshore waters of Maui Nui, Hawaii. Between 1995 and 2017, 1,312 distinctive individual odontocetes were photographically documented. Our photo-identification catalogs include 583 spinner dolphins (Stenella longirostris longirostris), 164 bottlenose dolphins (Tursiops truncatus), 132 short-finned pilot whales (Globicephala macrorhynchus), 253 pantropical spotted dolphins (Stenella attenuata), 82 false killer whales (Pseudorca crassidens), 70 melon-headed whales (Peponocephala electra), 15 pygmy killer whales (Feresa attenuata), and 13 rough-toothed dolphins (Steno bredanensis). Of these, two false killer whales (2.44% of catalog), two spinner dolphins (0.34% of catalog), and three pantropical spotted dolphins (1.19% of catalog) displayed major dorsal fin disfigurements. Both spinner dolphins and two of the spotted dolphins had multiple resights spanning several years, with one spotted dolphin having a 16-year span between resights. The two false killer whales with bent dorsal fins did not have any resights and were only sighted once throughout the study period. We also present the first progression of dorsal fin collapse after a significant injury to the leading edge of a spinner dolphin. Results from this research expand our knowledge on injuries to marine mammals and the survivorship of wild dolphins with dorsal fin injuries and contribute to the management of odontocetes in Hawaii, where interactions with fishing gear are a significant conservation issue. [ABSTRACT FROM AUTHOR]

The embryology of cetaceans documents features that elucidate the interaction between form and function in modern species, as well as their evolution from extinct ones. Prenatal specimens of the dolphin Stenella attenuata demonstrate critical aspects of the embryonic and fetal development of cetaceans, the pharyngeal arches, ear ossicles, nasal opening, teeth, fore limb, hind limb, and flukes. In addition, specimens of the bowhead whale (Balaena mysticetus) illustrate the development of baleen and hair. [ABSTRACT FROM AUTHOR]

The article presents the first report of sperm whale (Physeter macrocephalus) attacks by killer whales (Orcinus orca) in the Gulf of Mexico. It states that an interaction between sperm whales and killer whales was observed using a vessel doing mid-water trawling operations in the gulf. It also says that killer whales have been observed attacking other marine mammals including pantropical spotted dolphins (Stenella attenuata).

The distribution and abundance of marine mammals along the United States coast of the Gulf of Mexico are well-documented, but similar studies for the Mexican coast of the Gulf of Mexico are lacking. Furthermore, these animals are important indicators of the marine ecosystem health, and scientific research is needed to develop appropriate conservation strategies. Thus, the objective of this study was to determine the diversity, distribution, and relative abundance of marine mammals in the northern coasts of Veracruz, Mexico. Boat-based surveys and aerial surveys were carried out from March 2005 to August 2006. The following species were observed: bottlenose dolphins (Tursiops truncatus), spotted dolphin (Stenella attenuata), spinner dolphin (S. longirostris), roughtoothed dolphin (Steno bredanensis), pilot whale (Globicephala macrorhynchus), and an unidentified species of a dolphin. Also, the remains of a sperm whale (Physeter macrocephalus) and a humpback whale (Megaptera novaeangliae) were observed. The Margalef Diversity Index showed a value of 1.82 for the entire study area. There were differences in the species sightings across seasons. The abundance for the entire study area was 10,824 (%CV 25.05); the density was 1.45 cetaceans/km2 (%CV 25.05), and the cluster density was 0.71 cetaceans/km2 (%CV 15.25). The dry season showed a relative abundance of 1.98 cetaceans/h; the rainy season, 1.07 cetaceans/h; and the cold front season, 1.28 cetaceans/h. This is a first glimpse of cetacean population sizes in Mexico. Mexican authorities consider all marine mammal species to be under some conservation status, but they do not have population estimates. Supplementary studies will extend the information presented here for further refinement of cetacean diversity and distribution in Mexican waters of the Gulf of Mexico. Special effort is needed in deeper waters of the Mexican part of the Gulf of Mexico since there is no information about diversity and abundance of marine mammals for those areas. [ABSTRACT FROM AUTHOR]