Luksenburg, J.A.

Abstract:

Aruba, located close to the coasts of Colombia and Venezuela, is one of the most densely populated islands in the Caribbean and supports a wide range of marine-related socio-economic activities. However, little is known about the impacts of human activities on the marine environment. Injuries in marine mammals can be used to examine interactions with human activities and identify potential threats to the survival of populations. The prevalence of external injuries and tooth rake marks were examined in Atlantic spotted dolphin (Stenella frontalis) (n=179), bottlenose dolphin (Tursiops truncatus) (n=76) and false killer whale (Pseudorca crassidens) (n=71) in Aruban waters using photo identification techniques. Eleven injury categories were defined and linked to either human-related activities or natural causes. All injury categories were observed. In total, 18.7% of all individuals had at least one injury. Almost half (41.7%) of the injuries could be attributed to human interactions, of which fishing gear was the most common cause (53.3%) followed by propeller hits (13.3%). Major disfigurements were observed in all three species and could be attributed to interactions with fishing gear. The results of this study indicate that fishing gear and propeller hits may pose threats to small and medium-sized cetaceans in Aruban waters. Thus, long-term monitoring of population trends is warranted. Shark-inflicted bite wounds were observed in Atlantic spotted dolphin and bottlenose dolphin. Bite wounds of cookie cutter sharks (Isistius sp.) were recorded in all three species, and include the first documented record of a cookie cutter shark bite in Atlantic spotted dolphin. This is one of the few studies which investigates the prevalence of injuries in cetaceans in the Caribbean. Further study is necessary to determine to which extent the injuries observed in Aruba affect the health and survival of local populations. 

Abstract:

1. Killer whales Orcinus orca are found in all oceans of the world, but most of our knowledge on the species comes from studies conducted at higher latitudes. Studies on killer whales in the Caribbean have been scarce.

2. We compiled 176 records of killer whales from the Caribbean, including 95 previously unreported records and 81 records recovered from the literature, consisting of 27 capture or kill records, 4 stranding records and 145 sighting records.

3. Our results indicate that killer whales are widespread in the Caribbean Sea and can be found year-round in the region. Mean group size was 3.7 animals. A diversity of prey items was recorded, including sea turtles and marine mammals and possibly fish. We cannot exclude ecotype or morphotype-specific dietary specialization in the Caribbean population. A preliminary morphological analysis of 10 characters in 52 individuals from 21 different groups suggests that Caribbean killer whales do not represent any of the four Antarctic and subantarctic types, type 1 from the northwest Atlantic, or ‘resident’ and ‘transient’ killer whales from the northwest Pacific. Some Caribbean killer whales share a combination of characters typical of type 2 in the North Atlantic, whereas others share those typical of ‘offshore’ killer whales in the northwest Pacific. The significance of this is unclear. Comparison of Caribbean killer whales to previously described morphotypes and ecotypes is hampered by the lack of detailed, quantitative data on variation within other types, as well as by the lack of comparisons of genetic diversity.

4. Our study adds to the growing knowledge of the diversity of killer whales worldwide but underscores that additional research is warranted in the tropics. 

Abstract:

Aruba is one of the most densely populated islands in the Caribbean. However, very little is known about its cetaceans. In 2010 and 2011, a total of 19721 km (1686 h) boat-based surveys over nearshore transects resulted in 117 positively-identified sightings comprising eight species. New records are also added for one of three previously-documented species. Five additional species were documented from strandings or reports by others. This brings the total number of cetacean species identified in Aruban waters to 16, of which nine are authenticated here for the first time. Atlantic spotted dolphin (Stenella frontalis (N 1⁄4 59) and bottlenose dolphin (Tursiops truncatus) (N 1⁄4 33) were the most frequently observed species, with sightings of both year-round, followed by spinner dolphin (S. longirostris) and false killer whale (Pseudorca crassidens). Additional species recorded are pantropical spotted dolphin (S. attenuata), striped dolphin (S. coeruleoalba), common dolphin (Delphinus capensis), rough-toothed dolphin (Steno bredanensis), short-finned pilot whale (Globicephala macrorhynchus), killer whale (Orcinus orca), Risso’s dolphin (Grampus griseus), humpback whale (Megaptera novaeangliae), Bryde’s/Eden’s whale (Balaenoptera brydei/edeni), sperm whale (Physeter macrocephalus) and an unidentified beaked whale (Mesoplodon sp.). All cetaceans were sighted within 22 km of the coast in relatively shallow waters. Sighting rate was low (0.69 cetacean sightings per 100 km). Sightings of calves and neonates indicate that Aruba may be a nursing or breeding area for some species. The presence of several species of cetaceans in Aruba’s coastal waters year-round indicates that status and threat assessments are needed to protect them. 

Abstract:

Very little information exists about the cetaceans of Aruba, Curaçao and Bonaire (ABC Islands), in the southern Caribbean. During the first dedicated cetacean surveys for the coastal waters of Aruba, photographic evidence for the occurrence of false killer whales (Pseudorca crassidens), Atlantic spotted dolphins (Stenella frontalis) and spinner dolphins (Stenella longirostris) was obtained. These represent the first confirmed records of P. crassidens and S. frontalis for the ABC Islands and of S. longirostris for Aruba. 

1. Effective conservation management requires a solid understanding of social and economic factors, in addition to biological factors affecting what is to be conserved. Aruba is one of the most densely populated islands in the Caribbean and its already high number of tourists is still increasing. No commercial whale-watching operations are offered yet on the island. This provides a rare opportunity to document knowledge of and values concerning marine mammals before the introduction of whale-watching operations.

2. In 2010, a survey was conducted to investigate the awareness and attitudes of resident Arubans (n = 204) and tourists (n = 198) towards marine mammals and their conservation on Aruba. Knowledge of the local marine mammal community was low for both groups. Most participants would support more stringent legislation for protecting marine mammals in Aruba. Overall concern regarding threats to marine mammals was high and oil spills, chemical pollution, litter and sewage were identified as the most serious threats. A large proportion of residents (84.2%) and tourists (83.6%) were interested in, and willing to pay for, viewing marine mammals. Both groups preferred to see marine mammals in the wild rather than in captivity.

3. This is the first study that investigates the attitudes of people towards marine mammals and their conservation in a country that does not have marine mammal related tourism yet. This study suggests that strong support for marine mammal conservation issues does not critically depend on detailed knowledge of the local marine mammal community, or on the availability of whale-watching operations.