Dolphin Watching and Compliance to Guidelines Affect Spinner Dolphins’ (Stenella longirostris) Behaviour in Reunion Island

Marine wildlife tourism has rapidly developed in Reunion Island, due to a large demand for interactions with a resident population of spinner dolphins (Stenella longirostris). The presence of dolphin-watching vessels close to dolphin groups can cause short-term impacts on their behaviour; cumulative incidences likely result in deleterious long-term impacts on the population. Using scan sampling, we collected behavioural data on spinner dolphins to evaluate the short-term effects of dolphin watching on their behaviour. The dolphins were less likely to begin socialising or diving while travelling and more likely to stay travelling and milling in the presence of vessels. Additionally, activity budgets for resting and socialising decreased simultaneously with increased travelling and milling. Avoidance responses significantly increased with an increase in the number of vessels and non-compliance with the local dolphin-watching guidelines. These behavioural responses are likely to have energetic costs for the dolphins, which may lead to decreased survival and reproductive success at individual and population levels. More restrictive regulations, increased surveillance and animal-based measures are key tools to adapt the conservation efforts in Reunion Island. Further studies on the island’s resident dolphin populations are necessary to ensure the continuity of dolphin-watching activities in a sustainable manner.

Investigating Spinner Dolphin (Stenella longirostris) Occurrence and Acoustic Activity in the Maui Nui Region

Hawaiian spinner dolphins (Stenella longirostris) rest during the day in the islands’ coastal waters where they are susceptible to human disturbance. Due to concerns over the negative impacts of human activity, the Pacific Islands Regional Office of the National Oceanic and Atmospheric Administration (NOAA) has proposed a 50-yard approach rule for spinner dolphins and is also considering time-area closures of certain important spinner dolphin resting areas. However, gaps still persist in the understanding of how spinner dolphin populations on different Hawaiian Islands use coastal waters, raising questions about the efficacy of the proposed rules. To better understand how spinner dolphins use the waters in the Maui Nui region (Maui, Moloka‘i, Lāna‘i, and the ‘Au‘au channel), a study was conducted using a combination of passive acoustic monitoring and vessel surveys to document spinner dolphin occurrence and movements. Bottom-moored acoustic recorders were deployed at eight locations in Maui Nui, and at one previously established resting bay off west O‘ahu for comparison. The amount of whistles, clicks, and burst pulses at each location was quantified and averaged by the hour of the day. Acoustic activity was greater at the O‘ahu site than at any of the Maui Nui sites, and was greatest between sunrise and noon. Acoustic activity and vessel surveys both reveal that spinner dolphins occur and exhibit resting behaviors in the ‘Au‘au channel between Maui and Lāna‘i, and also along west Maui and southeast Lāna‘i. Spinner dolphins resting in a channel between islands appears to be unique to Maui Nui and differs from resting patterns described along Hawai‘i Island and O‘ahu. Because spinner dolphins appear to use both the coastlines and the channel to rest in Maui Nui, the 50-yard approach rule appears to be a more suitable management option for the region than time-area closures.

Listado anotado de los mamíferos marinos de El Salvador

Se registra la presencia de cinco especies de la familia Otariidae, tres especies de la familia Balaenopteridae, una especie de la familia Eschiteridae, doce especies de la familia Delphinidae, una especie de la familia Kogiidae, una especie de la familia Physeteridae y tres especies de la familia Ziphidae: un total de 26 especies de mamíferos marinos. La mayoría de especies se conocen por varamientos; otras, se basan sobre prospecciones de investigación. Seis especies son accidentales, ya que no ocurren de manera natural en aguas de Centroamérica. Ocho especies son migratorias y 12 especies son residentes y ocurrentes normales en aguas pelágicas. Cuatro especies, se considera, ocurren frecuentemente en las aguas costeras: la Ballena jorobada (Megaptera novaeangliae), el Delfín manchado (Stenella attenuata), el Delfín tornillo (Stenella longirostris) y el Delfín nariz de botella (Tursiops truncatus). Cinco especies están incluidas bajo amenaza o en peligro a nivel mundial.

Better educational signage could reduce disturbance of resting dolphins

Spinner dolphins on Hawai‘i Island’s west coast (Stenella longirostris longirostris) rest by day in protected bays that are increasingly popular for recreation. Because more frequent interactions of people with these dolphins is likely to reduce rest for dolphins and to explain recent decline in dolphin abundance, the National Oceanic and Atmospheric Administration (NOAA) proposed stricter rules regarding interactions with spinner dolphins near the main Hawaiian Islands and plans to increase enforcement. Simultaneous investment in public education about both interaction rules and their biological rationale has been and is likely to be relatively low. To test the hypothesis that more educational signage will reduce human-generated disturbance of dolphins, a paper questionnaire was distributed to 351 land-based, mostly unguided visitors at three dolphin resting bays on Hawai‘i Island’s west coast. Responses indicated that visitors wanted to see dolphins, were ignorant of interaction rules, were likely to read signs explaining rules and their biological rationales, and were likely to follow known rules. Therefore, investment in effective educational signage at dolphin resting bays is recommended as one way to support conservation of spinner dolphins on Hawai‘i Island’s west coast and similar sites in the Hawaiian archipelago.

Uso de assobios na identificação de delfinídeos (Odontoceti: Delphinidae) para o oceano Atlântico Sul ocidental

O grupo dos Cetáceos, formado basicamente por baleias, botos e golfinhos evoluiu em um ambiente que propiciou o desenvolvimento de sistemas complexos de comunicação acústica. Devido às suas propriedades físicas, o som viaja cerca de cinco vezes mais rápido na água do que no ar, sendo uma das energias mais eficientes no meio aquático. Sendo assim, os cetáceos são animais vocalmente ativos. Golfinhos da família Delphinidae destacam-se por apresentarem um complexo comportamento vocal, formado por assobios, cliques de ecolocalização e pulsos explosivos. Esses sons são utilizados na realização de diversas tarefas, tais como socialização, caça, navegação e discriminação de objetos. Além de características morfológicas, como posição da nadadeira dorsal, presença de manchas ou padrões de coloração, os sinais acústicos produzidos por esses animais podem ser utilizados na identificação ao nível de espécie. Bioacústica é a ciência responsável por estudar os mecanismos e forças envolvidas na produção, recepção e propagação do som. Essa área do conhecimento tem crescido nos últimos anos para o estudo de cetáceos devido às dificuldades em estudar esses animais em seu habitat natural, que permanecem submersos por longos minutos e apresentam um comportamento que dificulta a aproximação de pesquisadores para identificação da espécie. Algoritmos de classificação acústica têm sido desenvolvidos e aprimorados por se mostrarem extremamente úteis em situações que impossibilitam ou dificultam a observação de delfinídeos. Condições meteorológicas adversas como ventos, chuvas, estado do mar alto, períodos noturnos e de baixa visibilidade podem comprometer a identificação visual e o estudo com esses mamíferos. Com base nisso, este trabalho buscou classificar espécies de delfinídeos com base apenas em seu repertório acústico para o oceano Atlântico Sul ocidental. Foi possível identificar acusticamente três espécies: Delphinus delphis, Stenella frontalis e Stenella longirostris. Essas espécies foram frequentemente avistadas durante o Projeto Talude, uma pesquisa realizada entre 2013 a 2015 nos taludes sul e sudeste do Brasil. Provavelmente essas espécies também estavam acusticamente disponíveis quando condições meteorológicas não propícias não permitiram a identificação visual pelos observadores de bordo. Trabalhos como esse podem contribuir com a conservação dos cetáceos, que sofrem constantemente com os impactos causados por humanos em seu ambiente.

Identifying spinner dolphin Stenella longirostris longirostris movement and behavioral patterns to inform conservation strategies in Maui Nui, Hawai‘i

Spinner dolphins Stenella longirostris longirostris in Hawai‘i exhibit a predictable diurnal behavioral pattern which makes them vulnerable to human disturbance: feeding at night in offshore waters and resting during daytime in bays. There is concern that human activity, such as swimming with and viewing wild dolphins from vessels, is altering their natural behavioral patterns and preventing them from having adequate rest. In light of this, state and federal management agencies are proposing enhanced protection measures. Research on spinner dolphins has largely focused off Hawai‘i Island and there are insufficient data from Maui Nui (Maui, Lāna‘i, Kaho‘olawe, and Moloka‘i) to inform appropriate management measures for the genetically distinct stock that resides around these islands. Using location data from 316 encounters between 1996 and 2019, we identified 2 hotspots for spinner dolphins within the region, located along west Maui and south Lāna‘i. The predominant behavior observed was traveling, and there was little resting behavior documented throughout the study period, with no resting behavior observed along the coastline of Maui. Our findings revealed that spinner dolphins use a wide variety of available habitat in Maui Nui and were observed resting both near the shore of Lāna‘i and in the channels between islands. Based upon these findings, the proposed lone area for closure in south Maui is inadequate for providing protection to spinner dolphins during resting hours, and we propose that the identified hotspots be considered as additional sites for closures, in addition to an approach limit for vessels transiting Maui Nui.