For more than a decade, interactions between humans and Hawaiian spinner dolphins in their resting bays have been a concern for members of the general public, managers, scientists, policymakers, and ...tour operators. Hawaiian spinner dolphins are the target of a large wildlife tourism industry due to their predictable daytime resting behavior and presence in coastal areas. Using results from passive acoustic monitoring between January 2011 and March 2013 on the Kona coast of Hawai‛i Island, USA, the relative importance of four known Hawaiian spinner dolphin resting bays, the contribution of anthropogenic noise including vessel noise to the four bay soundscapes, and the dolphins' response to human activities were assessed. Here the findings are summarized and visualized and recommendations are provided for action to regulate directed dolphin watching and ensuing unauthorized takes under the Marine Mammal Protection Act of 1972. These findings and recommendations have implications for the federal government's ongoing efforts to implement rules that protect Hawaiian spinner dolphins in their resting bays.
As with other nature-based tourism ventures, whale shark tourism is expanding rapidly worldwide, which highlights the need to understand more about the nature of these activities. Records of ...interactions between tour operators and whale sharks at Ningaloo Reef, Western Australia (22.5°S, 113.5°E) were obtained from the Western Australian Department of Parks and Wildlife from 2006 to 2010 and evaluated to determine the scale of the tourism operations and the spatial and temporal distribution of interactions. The number of whale shark tours at Ningaloo increased by approx. 70% (520–886 tours per year) and the number of interactions with whale sharks by 370% between 2006 (694) and 2010 (3254). The locations of whale shark interactions recorded in logbooks (2006–2009) and electronic monitoring systems (2009 and 2010) were used to plot the smoothed densities of tour operator interactions with whale sharks. Generalised linear models were used to investigate how the presence/absence and number of whale shark interactions at North and South Ningaloo were influenced by the distance to the reef crest, the distance to passages and their interaction terms for the aggregated five-year data set. Over the five years, distance to the reef crest was the best predictor of the presence/absence of whale shark interactions at both North (interactions concentrated within 3 km of the reef crest) and South Ningaloo (interactions within 6 km of the reef crest) followed by distance to passages. The reef passages are very significant areas for tourism interactions with whale sharks at Ningaloo. The distribution of interactions at North and South Ningaloo varied from year to year, particularly in the strong La Niña year of 2010, when average sea surface temperatures remained above 24 °C and whale sharks were observed much later in the year than previously (late August). This study demonstrates the value of the data collected by the tour operators at Ningaloo Reef and managed by a government agency for the conservation of whale sharks and sustainable whale shark tourism.
In Shark Bay, Western Australia, bottlenose dolphins Tursiops sp. carry conical sponges Echinodictyum mesenterinum on their rostra in the only documented cetacean foraging behaviour using a tool ...('sponging'). In this study, we examined the influence of various ecological factors on live sponge distribution and the occurrence of sponging in parts of the western gulf of Shark Bay. We assessed sponge distribution and seagrass cover along 12 transects of approximately 11 km length, by recording sponges and seagrass in a total of 1380 quadrats (1 x 1 m), of which 56 quadrats contained conical sponges. The occurrence of sponging dolphins ('spongers') was documented along 10 of these 12 transects. The distribution of conical sponges was negatively correlated with the distribution of seagrass: no conical sponges were observed in water depths of 12 m. A digital elevation model, created from the sample depth data, identified channels in the region. Binary logistic and Poisson log-linear generalised linear models showed that water depth and bathymetric features including channel, substrate and slope were significant in predicting the occurrence and the mean number of conical sponges, as well as that of seagrass. Conical sponge distribution was positively correlated with the distribution of sponging, indicating that ecological factors influence where sponging occurs. The greater number of spongers found in this region may be explained by the larger area of habitat suitable for conical sponges in the western than the eastern gulf of Shark Bay.
Hawaiian spinner dolphins display predictable daily behavior, using shallow bays to rest during the daytime, bays that are also frequented by humans. All previous research on the potential response ...of Hawaiian spinner dolphins to human activity has been conducted visually, at the surface. In this study we take a different approach by using passive acoustic monitoring to analyze dolphin behavior and assess whether human activity affects the behavior of the animals. We used days (n=99) and hours (n=641) when dolphins were confirmed present in visual surveys between January 9, 2011 and August 15, 2012 and metrics generated from concomitant 30-second sound recordings (n=9615). Previous research found that the dolphins were predictably silent during rest and that acoustic activity matched general activity of the dolphins with higher acoustic activity before and after rest, and silence during rest. The daily pattern of dolphin whistle activity in Bay 2 and 4 (Kealakekua and Kauhako) matched what would be expected from this earlier work. However, in Bay 1 and 3 (Makako and Honaunau) there was no drop in dolphin whistle activity during rest. After assessing the relationship between time of day and dolphin acoustic activity, data on human presence were used to determine how variability in the dolphins’ acoustic activity might be explained by human activity (i.e. the number of vessels, kayaks and swimmer snorkelers present). Bay 2, the bay with the most human activity, showed no relationship between dolphin whistle activity and human presence (either vessels, kayaks, or swimmer/snorkelers). Although the relationships were weak, Bay 1 displayed a positive relationship between dolphin whistle activity and the number of vessels and swimmer/snorkelers present in the bay. Bay 4 also showed a positive relationship between dolphin whistle activity and the number of swimmer snorkelers. We also documented less sound being added to the soundscape with each additional vessel in Bay 2 when compared to Bay 1, a bay with dolphin-focused activities. We hypothesize it is not the magnitude of the activity but the focus of the activity that matters and suggest that the effect of human activity on spinner dolphin acoustic behavior should be explored in future studies. These results have implications for designing future studies as well as for ongoing efforts to protect Hawaiian spinner dolphins in their resting bays.
The expansion of the world's merchant fleet poses a great threat to the ocean's biodiversity. Collisions between ships and marine megafauna can have population-level consequences for vulnerable ...species. The Endangered whale shark (Rhincodon typus) shares a circumglobal distribution with this expanding fleet and tracking of movement pathways has shown that large vessel collisions pose a major threat to the species. However, it is not yet known whether they are also at risk within aggregation sites, where up to 400 individuals can gather to feed on seasonal bursts of planktonic productivity. These “constellation” sites are of significant ecological, socio-economic and cultural value. Here, through expert elicitation, we gathered information from most known constellation sites for this species across the world (>50 constellations and >13,000 individual whale sharks). We defined the spatial boundaries of these sites and their overlap with shipping traffic. Sites were then ranked based on relative levels of potential collision danger posed to whale sharks in the area. Our results showed that researchers and resource managers may underestimate the threat posed by large ship collisions due to a lack of direct evidence, such as injuries or witness accounts, which are available for other, sub-lethal threat categories. We found that constellations in the Arabian Sea and adjacent waters, the Gulf of Mexico, the Gulf of California, and Southeast and East Asia, had the greatest level of collision threat. We also identified 39 sites where peaks in shipping activity coincided with peak seasonal occurrences of whale sharks, sometimes across several months. Simulated collision mitigation options estimated potentially minimal impact to industry, as most whale shark core habitat areas were small. Given the threat posed by vessel collisions, a coordinated, multi-national approach to mitigation is needed within priority whale shark habitats to ensure collision protection for the species.
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•The marine biosphere is at risk from expanding maritime human activities.•Collisions between large ships and marine megafauna are in need of management attention.•Shipping was measured in over 50 global whale shark aggregation sites.•Peaks in shipping activity often coincided with peak seasonal occurrences of whale sharks.•Changes to ship speed or transiting routes can be targeted in small, localised zones.
In Shark Bay, Western Australia, bottlenose dolphinsTursiopssp. carry conical spongesEchinodictyum mesenterinumon their rostra in the only documented cetacean foraging behaviour using a tool ...(‘sponging’). In this study, we examined the influence of various ecological factors on live sponge distribution and the occurrence of sponging in parts of the western gulf of Shark Bay. We assessed sponge distribution and seagrass cover along 12 transects of approximately 11 km length, by recording sponges and seagrass in a total of 1380 quadrats (1 × 1 m), of which 56 quadrats contained conical sponges. The occurrence of sponging dolphins (‘spongers’) was documented along 10 of these 12 transects. The distribution of conical sponges was negatively correlated with the distribution of seagrass: no conical sponges were observed in water depths of <10 m and no seagrasses were found at depths of >12 m. A digital elevation model, created from the sample depth data, identified channels in the region. Binary logistic and Poisson log-linear generalised linear models showed that water depth and bathymetric features including channel, substrate and slope were significant in predicting the occurrence and the mean number of conical sponges, as well as that of seagrass. Conical sponge distribution was positively correlated with the distribution of sponging, indicating that ecological factors influence where sponging occurs. The greater number of spongers found in this region may be explained by the larger area of habitat suitable for conical sponges in the western than the eastern gulf of Shark Bay.
Hawaiian spinner dolphins display predictable daily behavior, using shallow bays to rest during the daytime. The frequency and intensity of the interactions between humans and dolphins in these bays ...has prompted concern for the animals. All previous research on the dolphins’ response to human activity has been conducted visually. In contrast, here we evaluate whether dolphins acoustically respond to human activity. Previous research found that the dolphins were silent during rest and that acoustic activity matched general behavioral state. Therefore, we expected to see higher dolphin whistle activity before and after peak resting time and low activity to indicate rest. The daily pattern of dolphin whistle activity in two of the four bays matched what we expected. However, in two bays we did not find a drop in dolphin whistle activity. With regards to the acoustic response of the animals to human activity, we found relationships between the number of vessels and dolphin acoustic activity in a bay with dolphin-focused activities but not in the bay with the most activity. Our results suggest that the key factor is not the sheer presence or magnitude of human activities but rather the directed interactions and dolphin focused activities that elicit a response.
Reliable population estimates are critical to implement effective management strategies. The Hawai'i Island spinner dolphin (Stenella longirostris) is a genetically distinct stock that displays a ...rigid daily behavioural pattern, foraging offshore at night and resting in sheltered bays during the day. Consequently, they are exposed to frequent human interactions and disturbance. We estimated population parameters of this spinner dolphin stock using a systematic sampling design and capture-recapture models. From September 2010 to August 2011, boat-based photo-identification surveys were undertaken monthly over 132 days (>1,150 hours of effort; >100,000 dorsal fin images) in the four main resting bays along the Kona Coast, Hawai'i Island. All images were graded according to photographic quality and distinctiveness. Over 32,000 images were included in the analyses, from which 607 distinctive individuals were catalogued and 214 were highly distinctive. Two independent estimates of the proportion of highly distinctive individuals in the population were not significantly different (p = 0.68). Individual heterogeneity and time variation in capture probabilities were strongly indicated for these data; therefore capture-recapture models allowing for these variations were used. The estimated annual apparent survival rate (product of true survival and permanent emigration) was 0.97 SE plus or minus 0.05. Open and closed capture-recapture models for the highly distinctive individuals photographed at least once each month produced similar abundance estimates. An estimate of 221 plus or minus 4.3 SE highly distinctive spinner dolphins, resulted in a total abundance of 631 plus or minus 60.1 SE, (95% CI 524-761) spinner dolphins in the Hawai'i Island stock, which is lower than previous estimates. When this abundance estimate is considered alongside the rigid daily behavioural pattern, genetic distinctiveness, and the ease of human access to spinner dolphins in their preferred resting habitats, this Hawai'i Island stock is likely more vulnerable to negative impacts from human disturbance than previously believed.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The bycatch of small cetaceans in commercial fisheries is a global wildlife management problem. We used data from skippers' logbooks and independent observers to assess common bottlenose dolphin ...(Tursiops truncatus) bycatch patterns between 2003 and 2009 in the Pilbara Trawl Fishery, Western Australia. Both datasets indicated that dolphins were caught in all fishery areas, across all depths and throughout the year. Over the entire datasets, observer reported bycatch rates (n = 52 dolphins in 4,124 trawls, or 12.6 dolphins/1,000 trawls) were ca. double those reported by skippers (n = 180 dolphins in 27,904 trawls, or 6.5 dolphins/1,000 trawls). Generalised Linear Models based on observer data, which better explained the variation in dolphin bycatch, indicated that the most significant predictors of dolphin catch were: (1) vessel - one trawl vessel caught significantly more dolphins than three others assessed; (2) time of day - the lowest dolphin bycatch rates were between 00:00 and 05:59; and (3) whether nets included bycatch reduction devices (BRDs) - the rate was reduced by ca. 45%, from 18.8 to 10.3 dolphins/1,000 trawls, after their introduction. These results indicated that differences among vessels (or skippers' trawling techniques) and dolphin behavior (a diurnal pattern) influenced the rates of dolphin capture; and that spatial or seasonal adjustments to trawling effort would be unlikely to significantly reduce dolphin bycatch. Recent skipper's logbook data show that dolphin bycatch rates have not declined since those reported in 2006, when BRDs were introduced across the fishery. Modified BRDs, with top-opening escape hatches from which dolphins might escape to the surface, may be a more effective means of further reducing dolphin bycatch. The vulnerability of this dolphin population to trawling-related mortality cannot be assessed in the absence of an ongoing observer program and without information on trawler-associated dolphin community size, broader dolphin population size and connectivity with adjacent populations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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