Boat Strikes Research Articles

Offshore Earthquakes Do Not Influence Marine Mammal Stranding Risk on the Washington and Oregon Coasts.

Simple SummaryMarine mammals stranding on coastal beaches is not unusual. However, there appears to be no single cause for this, with several causes being probable, such as starvation, contact with humans (for example boat strike or entanglement with fishing gear), disease, and parasitism. We evaluated marine mammal stranding off the Washington and Oregon coasts and looked at offshore earthquakes as a possible contributing factor. Our analysis showed that offshore earthquakes did not make marine mammals more likely to strand. We also analysed a subset of data from the north of Washington State and found that non-adult animals made up a large proportion of stranded animals, and for dead animals the commonest cause of death was disease, traumatic injury, or starvation.The causes of marine mammals stranding on coastal beaches are not well understood, but may relate to topography, currents, wind, water temperature, disease, toxic algal blooms, and anthropogenic activity. Offshore earthquakes are a source of intense sound and disturbance and could be a contributing factor to stranding probability. We tested the hypothesis that the probability of marine mammal stranding events on the coasts of Washington and Oregon, USA is increased by the occurrence of offshore earthquakes in the nearby Cascadia subduction zone. The analysis carried out here indicated that earthquakes are at most, a very minor predictor of either single, or large (six or more animals) stranding events, at least for the study period and location. We also tested whether earthquakes inhibit stranding and again, there was no link. Although we did not find a substantial association of earthquakes with strandings in this study, it is likely that there are many factors influencing stranding of marine mammals and a single cause is unlikely to be responsible. Analysis of a subset of data for which detailed descriptions were available showed that most live stranded animals were pups, calves, or juveniles, and in the case of dead stranded mammals, the commonest cause of death was trauma, disease, and emaciation.

Supplemental feeding and other anthropogenic threats to green turtles (Chelonia mydas) in the Canary Islands

Green turtles are found in the waters of the Canary Islands but little is known about the ecology and anthropogenic pressures that threaten them. Our results have revealed that juvenile green turtles, ranging in curve carapace length from 26.9–81.0cm, are regularly found in the archipelago and originate from rookeries in both the eastern and western Atlantic. Photo-identification and satellite tracking showed high levels of site fidelity to coastal foraging grounds associated with seagrass meadows, but stable isotope analysis indicated animal-based omnivorous diets after settlement on the continental shelf, with no increase in the consumption of macrophytes as the turtles grew. Most turtles exhibited high levels of some blood biochemical markers associated with a high consumption of proteins and fat. In addition, we determined levels of some organic and inorganic pollutants. Supplemental feeding may also contribute to explain the high prevalence of hooking and boat strikes in the green turtles brought to wildlife rescue centers as compared with loggerhead turtles. Regulatory measures and surveillance should be urgently implemented in order to improve the status of the species in the archipelago.

Stranding Events of Kogia Whales along the Brazilian Coast.

The genus Kogia, which comprises only two extant species, Kogia sima and Kogia breviceps, represents one of the least known groups of cetaceans in the global ocean. In some coastal regions, however, stranding events of these species have been relatively common over the last decades. Stranding provides the opportunity to investigate the biology of these cetaceans and to explore the epidemiological aspects associated with the mortality of the organisms found on the beach. A number of disturbances (including pelagic fisheries, chemical pollution, boat strikes, and noise pollution) have been confirmed to pose a particular threat to the Kogia species. However, no study has yet investigated potential relationships between environmental conditions and stranding events. Here we analyse how a collection of environmental, physical, and biological variables, such as wind, sea surface temperature (SST), water depth, and chlorophyll-a, correlate to Kogia stranding events along the Brazilian coast. The results of our statistical analyses suggest that K. sima is more likely found in warm tropical waters, which provide an explanation for the high frequency of stranding in northeastern Brazilian coast. In contrast, K. breviceps appears to have a preference for temperate and productive waters. Wind speed results to be also an important factor for predicting Kogia strandings in Brazilian coast. Additionally, literature information in combination with our own data and analyses of stomach contents confirms that oceanic cephalopods constitute the primary nutritional source of both Kogia species. By using the available information as a qualitative proxy for habitat preference and feeding ecology, our study provides a novel and comprehensive assessment of Kogia stranding data in relation to environmental conditions along the Brazilian coast.

Endangered Florida panther population size determined from public reports of motor vehicle collision mortalities

Summary Reliably estimating the abundance of rare or elusive animals is notoriously difficult. An archetypical example is the endangered Florida panther, whose conservation status is intrinsically linked to population size, but for which reliable abundance information is lacking across its range. This is due not only to the inherent difficulty of sampling a rare and elusive species over a large geographic area, but also because of restricted scientific access to private land. Human interactions with wildlife are a regular occurrence, and interactions with non‐scientists constitute an important and underutilized source of information about species distribution and abundance. For example, motor vehicle collisions with Florida panthers are recurrent on the vast network of roads within the public and private lands comprising its range in southern Florida, USA. Capitalizing on a tendency for the public to report collisions with species of concern to wildlife officials, we describe a novel methodology using public reports along with routine telemetry monitoring data to produce the first statistically defensible population estimates for the Florida panther across its entire breeding range. In essence, our approach uses traffic volume and road density to estimate the probability of motor vehicle collision mortality from telemetered animals and models counts reported by the public accordingly. Despite low motor vehicle collision mortality probabilities, our methodology achieved abundance estimates of reasonable precision (29% CV) that was similar to that of previous panther studies using conventional approaches on much smaller study areas. While recovery criteria require establishment of three distinct populations of 240 Florida panthers, we found this single population may never have exceeded 150 individuals from 2000 to 2012. Synthesis and applications. By extracting critical demographic information from underutilized aspects of human–wildlife ecology, our citizen‐based approach can cost less than conventional alternatives and could conceivably be used for long‐term population monitoring of other species over broad geographic areas, for example from reports of avian wind farm collisions, beached whales or marine mammal boat strikes. An additional benefit is that it can be applied to historical data sets of carcass recovery programmes, in our case permitting abundance estimation over a 13‐year period.

Mass mortality of Northern Map Turtles (<em>Graptemys geographica</em>)

We report a mass mortality of Northern Map Turtles (Graptemys geographica [LeSueur, 1817]) on the north shore of Lake Erie, Ontario, Canada. Thirty-five dead adult females were recovered from a nesting area over a period of four weeks. Predation and boat strikes were both excluded as potential cause of death, but the actual cause could not be determined because of the poor condition of the carcasses. Other possible explanations for the mortality include poisoning, drowning, and infection with an unidentified pathogen. Mass mortality in long-lived species, such as turtles, can have long-term effects on population growth and is a cause for concern in a species at risk.

Marine turtle mortalities along the Tamil Nadu coast of India and the need for turtle-friendly fisheries

In the past two decades, sea turtle mortality has increased due to a variety of anthropogenic activities along the Nagapattinam and Chennai coast region in Tamil Nadu, South India. Weekly field surveys were conducted over an eight-month period from December 2013 to July 2014 to monitor the mortality of turtles in these coastal areas, revealing a notable disruption in the nesting activity of the turtles during January–March; the worst affected were mature individuals. Anthropogenic activities like boat strikes and fishing activity were recorded as the major causes of turtle death within this region. This paper highlights the need for better turtle monitoring systems within this part of South India, particularly for endangered species like the olive ridley turtle (Lepidochelys olivacea), whilst also suggesting suitable conservation measures to protect them.

Applying marketing to conservation: A case study on encouraging boater reporting of watercraft collisions with Florida manatees

We illustrate how the application of a traditional marketing approach can be used to address conservation problems. The conservation challenge at hand relates to the low number of reported boat strikes of the Florida manatee (Trichechuslatirostris), an endangered marine mammal that inhabits coastal Florida. Our objective was to assess why boaters do or do not call the authorities after their boat strikes a manatee and what can be done to increase the rate of reporting. Results of our online survey indicated that over 90% of subjects expressed a willingness to call the authorities if they strike a manatee with their boat. However, this self-reported sentiment has not resulted in frequent calls to the authorities by boaters involved in a collision with a manatee since records have been kept. The outcome of subsequent personal in-depth interviews suggested that most boaters do not know who to call or do not have the proper contact number. Based on our findings, we suggest the implementation of a decal to be positioned in a vessel's cockpit displaying the proper number to call to report a manatee incident. We also recommend including numbers for other marine emergencies on the decal. We discuss barriers to success that need to be considered and caution as to potential market failures.

What Caused the UK's Largest Common Dolphin (Delphinus delphis) Mass Stranding Event?

On 9 June 2008, the UK's largest mass stranding event (MSE) of short-beaked common dolphins (Delphinus delphis) occurred in Falmouth Bay, Cornwall. At least 26 dolphins died, and a similar number was refloated/herded back to sea. On necropsy, all dolphins were in good nutritive status with empty stomachs and no evidence of known infectious disease or acute physical injury. Auditory tissues were grossly normal (26/26) but had microscopic haemorrhages (5/5) and mild otitis media (1/5) in the freshest cases. Five lactating adult dolphins, one immature male, and one immature female tested were free of harmful algal toxins and had low chemical pollutant levels. Pathological evidence of mud/seawater inhalation (11/26), local tide cycle, and the relative lack of renal myoglobinuria (26/26) suggested MSE onset on a rising tide between 06∶30 and 08∶21 hrs (9 June). Potential causes excluded or considered highly unlikely included infectious disease, gas/fat embolism, boat strike, by-catch, predator attack, foraging unusually close to shore, chemical or algal toxin exposure, abnormal weather/climatic conditions, and high-intensity acoustic inputs from seismic airgun arrays or natural sources (e.g., earthquakes). International naval exercises did occur in close proximity to the MSE with the most intense part of the exercises (including mid-frequency sonars) occurring four days before the MSE and resuming with helicopter exercises on the morning of the MSE. The MSE may therefore have been a “two-stage process” where a group of normally pelagic dolphins entered Falmouth Bay and, after 3–4 days in/around the Bay, a second acoustic/disturbance event occurred causing them to strand en masse. This spatial and temporal association with the MSE, previous associations between naval activities and cetacean MSEs, and an absence of other identifiable factors known to cause cetacean MSEs, indicates naval activity to be the most probable cause of the Falmouth Bay MSE.

Are boat strikes a threat to sea turtles in the Galapagos Marine Reserve?

Impacts on sea turtle populations from fisheries bycatch, climate change, habitat destruction and poaching have been widely discussed, but little is known about boat strikes as a potential threat to sea turtles. Here we present data on Pacific green turtles (Chelonia mydas) that suffered boat strikes in the Galapagos Marine Reserve at nesting beaches at Isabela Island and from foraging sites at San Cristobal Island from 2008 to 2011. Tourism in Galapagos has increased to more than 180,000 visitors a year and the boat traffic within the Marine Reserve poses a significant risk to sea turtles. Boat strikes were most frequent at foraging sites close to Puerto Baquerizo Moreno, a commercial and tourism port, where incidence varied between 16 and 20%. Incidence at nesting beaches was much lower with 3.7% of 4198 turtles showing injuries resulting from boat strikes. However, at the nesting beaches most of the impacts (59%) had occurred during the same nesting season while only 5% of the sea turtles observed at the foraging sites suffered their injuries during the study period. No data on survival rates from boat strike exist, however it is clear that many turtles die from the trauma caused by the impact. This report focuses on only the survivors; therefore the results represent a minimum estimate. Our study clearly shows that the overall threat from boat strikes has an important effect on the Galapagos green turtle population. Conservation management including speed limits in key turtle habitats are needed to improve their survival in the Galapagos Marine Reserve.

Puerto Rico and Florida manatees represent genetically distinct groups

The West Indian manatee (Trichechus manatus) populations in Florida (T. m. latirostris) and Puerto Rico (T. m. manatus) are considered distinct subspecies and are listed together as endangered under the United States Endangered Species Act. Sustained management and conservation efforts for the Florida subspecies have led to the suggested reclassification of the species to a threatened or delisted status. However, the two populations are geographically distant, morphologically distinct, and habitat degradation and boat strikes continue to threaten the Puerto Rico population. Here, 15 microsatellite markers and mitochondrial control region sequences were used to determine the relatedness of the two populations and investigate the genetic diversity and phylogeographic organization of the Puerto Rico population. Highly divergent allele frequencies were identified between Florida and Puerto Rico using microsatellite (F ST = 0.16; R ST = 0.12 (P < 0.001)) and mitochondrial (F ST = 0.66; Ф ST = 0.50 (P < 0.001)) DNA. Microsatellite Bayesian cluster analyses detected two populations (K = 2) and no admixture or recent migrants between Florida (q = 0.99) and Puerto Rico (q = 0.98). The microsatellite genetic diversity values in Puerto Rico (HE = 0.45; NA = 3.9), were similar, but lower than those previously identified in Florida (HE = 0.48, NA = 4.8). Within Puerto Rico, the mitochondrial genetic diversity values (π = 0.001; h = 0.49) were slightly lower than those previously reported (π = 0.002; h = 0.54) and strong phylogeographic structure was identified (F ST global = 0.82; Ф ST global = 0.78 (P < 0.001)). The genetic division with Florida, low diversity, small population size (N = 250), and distinct threats and habitat emphasize the need for separate protections in Puerto Rico. Conservation efforts including threat mitigation, migration corridors, and protection of subpopulations could lead to improved genetic variation in the endangered Puerto Rico manatee population.

Serum Amyloid A (SAA) as a Biomarker of Chronic Infection Due to Boat Strike Trauma in a Free-ranging Florida Manatee (Trichechus manatus latirostris) with Incidental Polycystic Kidneys

Watercraft-related trauma is the predominant cause of human-induced mortality in manatees (Trichechus manatus latirostris), a federal- and state-listed endangered species. Pyothorax (documented in this case report) and other secondary infections are common sequelae of inhalation of water and the open wounds caused by boat propellers. These secondary infections can lead to the demise of the animal weeks to months after the traumatic incident when external wounds have healed. Diagnosis of underlying disease on physical examination during capture and restraint can be difficult. Acute phase proteins, including serum amyloid A, fibrinogen, and albumin can be used to diagnose inflammatory disease in manatees and improve quality of medical care and husbandry. We also provide the first report of polycystic kidneys in Sirenians.

Sea turtle strandings reveal high anthropogenic mortality in Italian waters

Abstract Spatio‐temporal distribution and anthropogenic mortality factors were investigated in loggerhead turtles (Caretta caretta) found stranded or floating in the waters around Italy. A total of 5938 records for the period 1980–2008 were analysed concerning loggerhead turtles measuring from 3.8 to 97 cm curved carapace length (mean: 48.3 cm). Results highlighted the following conservation issues: (i) in the study area, anthropogenic mortality is higher than natural mortality; (ii) interaction with fisheries is by far the most important anthropogenic mortality factor; (iii) longlines are an important mortality factor in the southern areas; (iv) trawlers are the cause of high numbers of dead strandings in the north Adriatic; (v) entanglement in ghost‐gear or in other anthropogenic debris affects high numbers of turtles; and (vi) boat strikes are an important source of mortality in most areas but mostly in the warm seasons. Results also indicate that: (vii) the north Adriatic is the area with the highest turtle density; and (viii) the south Adriatic and to a lesser extent the surrounding areas of the north Adriatic and the Ionian, are important developmental areas for loggerhead turtles in the first years of life. Italy is in the centre of the Mediterranean Sea and borders major foraging areas for the loggerhead turtles in the region, and these results confirm previous concerns about the level of anthropogenic mortality in Italian waters. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Redescription of the genus Manta with resurrection of Manta alfredi (Krefft, 1868) (Chondrichthyes; Myliobatoidei; Mobulidae)

The taxonomic history of the genus Manta has been questionable and convoluted, with Manta having one of the most extensive generic and species synonymies of any living genus of cartilaginous fish. Having previously been considered a monotypic genus with a single recognized species, Manta birostris (Walbaum 1792), new evidence, in the form of morphological and meristic data, confirm that two visually distinct species occur, both with wide ranging distributions through many of the world’s oceans. Manta birostris stands as the most widely distributed member of the genus, while Manta alfredi (Krefft 1868), resurrected herein, represents a smaller, more tropical species. Separation of the two species is based on morphometric measurements and external characters including colouration, dentition, denticle and spine morphology, as well as size at maturity and maximum disc width. The two species of Manta are sympatric in some locations and allopatric in other regions. A visual key was constructed which highlights the conspicuous, diagnostic features of the two species using data collected throughout their respective geographical ranges. A third, putative species, referred to here as Manta sp. cf. birostris, in the Atlantic may be distinct from M. birostris, but further examination of specimens is necessary to clarify the taxonomic status of this variant manta ray. The results of this study will aid in the differentiation of members of this genus both in the field and in preserved specimens. The splitting of this long-standing monospecific genus will help to highlight the specific threats facing the different species of Manta (e.g. targeted fishing, bycatch fisheries, boat strikes and habitat degradation) and will ultimately assist in the correct assessment of their respective worldwide conservation status.

Immunosuppression Cascade in the Florida Manatee (&lt;I&gt;Trichechus manatus latirostris&lt;/I&gt;)

The Florida manatee (Trichechus manatus latirostris) is a federally endangered marine mammal that resides on both coasts of the Florida peninsula. The species faces many anthropogenic and natural threats, including boat strikes, exposure to harmful algal blooms, and cold water temperatures. We have developed a conceptual model that depicts how changes in the environment, such as reduced water temperature, can trigger an immunosuppressive cascade of interrelated diseases and pathological conditions ultimately leading to the death of the animal. Although the Florida manatee has a relatively robust immune system, rendering it resistant to several diseases, the onset of unfavorable environmental conditions has been shown to compromise the immune system, often leading to infections that make an animal more susceptible to opportunistic pathogens. In this paper, we review several common diseases of the Florida manatee and compare and contrast their symptoms. We then interrelate these diseases and generate a conceptual model of a cascade of immunosuppressive conditions originally triggered by adverse environmental conditions or one of the diseases. The end result of the cascade is the death of the animal.

Health Assessment, Antibiotic Treatment, and Behavioral Responses to Herding Efforts of a Cow-Calf Pair of Humpback Whales (&lt;I&gt;Megaptera novaeangliae&lt;/I&gt;) in the Sacramento River Delta, California

A mother and female calf humpback whale (Megaptera novaeangliae) pair were observed at an atypical location, 72 nmi inland in the Port of Sacramento, California, on 16 May 2007. Sequencing of mtDNA from a skin biopsy showed the cow to be an E1 haplotype, which is common in the California feeding population. Both animals had lacerations, suggesting sharp trauma from a boat strike. Photographs taken over 11 d showed generalized deterioration of skin condition and necrotic wound edges. Behavioral responses were recorded during attempts to move the animals downriver to the Pacific Ocean. The attempts included playback of alarm tones, humpback and killer whale sounds, banging hollow steel pipes (“Oikami pipes”), spraying water from fire hoses on the water surface, and utilizing tug and power boat engine noise and movement. None of these deterrents resulted in significant, consistent downstream movement by the whales. Antibiotic therapy (ceftiofur) was administered by a dart, representing the first reported antibiotic treatment of free-ranging live whales. After 11 d, the animals swam downstream from fresh water at Rio Vista to brackish water, and their skin condition noticeably improved 24 h later. The animals followed the deep-water channel through the Sacramento

Cause-specific temporal and spatial trends in green sea turtle strandings in the Hawaiian Archipelago (1982–2003)

We investigated cause-specific temporal and spatial trends in sea turtle strandings in the Hawaiian Archipelago. Five species of sea turtle were recorded in 3,861 strandings over a 22-year period (1982–2003). Green turtles comprised 97% of these strandings with size and gender composition reflecting the demographic structure of the resident green turtle population and relative green turtle abundance in Hawaiian waters. The cause of strandings was determined by necropsy based on a complete gross external and internal examination. Totally 75% of the 3,732 green turtle strandings were from Oahu where strandings occur year-round. The most common known cause of the green turtle strandings was the tumour-forming disease, fibropapillomatosis (28%) followed by hook-and-line fishing gear-induced trauma (7%), gillnet fishing gear-induced trauma (5%), boat strike (2.5%), and shark attack (2.7%). Miscellaneous causes comprised 5.4% of strandings whereas 49% of green turtle strandings could not be attributed to any known cause. Green turtle strandings attributable to boat strike were more likely from Kauai and Oahu while fibropapilloma strandings were more likely from Oahu and Maui. Hook-and-line gear strandings were more likely from Oahu due to higher per capita inshore fishing effort. The specific mortality rate (conditional probability) for fibropapillomatosis was 88%, 69% for gillnet gear and 52% for hook-and-line gear. The probability of a dead green turtle stranding increased from 1982 but levelled off by the mid-1990s. The declining mortality risk was because the prevalence and severity of fibropapillomatosis has decreased recently and so has the mortality risk attributable to gillnet gear. Despite exposure to disease and inshore fishing gears, the Hawaiian green turtle stock continues to recover following protection since the late 1970s. Nevertheless, measures to reduce incidental capture of sea turtles in coastal Hawaiian fisheries would be prudent, especially since strandings attributable to hook-and-line fishing gear have increased steadily since 1982.

Some Reproductive Parameters of an Estuarine Population of Indo-Pacific Bottlenose Dolphins (&lt;I&gt;Tursiops aduncus&lt;/I&gt;)

The Port River estuary (Adelaide, South Australia) supports a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) despite its heavily modified habitat. This paper reports the calving season, birth rate, calf mortality, and inter-birth interval of the resident population, all factors important in the conservation of this population. Between 1989 and 2005, 1,176 boat surveys were undertaken, covering all seasons for each year. All dolphins encountered were photographed, and their location, number, age category, and behaviour were recorded. Dolphin identity was determined a posteriori using photo-identification. Results indicated a calving season from December to March, which coincided with the maximum surface water temperature of the estuary. Inter-birth intervals were consistent with the literature—3.8 y when the previous calf was weaned and 1.7 y when the previous calf died—with the exception of one special case. Forty-five calves were born to resident females between 1989 and 2005, and the average crude birth rate was 0.064, which is similar to that found for other bottlenose dolphin populations. First-year calf mortality (30%) and mortality rate for calves prior to weaning (46%) were higher than mortality rates described for other locations. Minimal predation is thought to occur in the estuary, and there was no evidence of poor condition in the mothers, suggesting that the high mortality rates were caused by direct impacts on calves such as entanglements, boat strikes, deliberate attacks, or exposure to toxic pollution.

Material properties of manatee rib bone

AbstractWatercraft‐related mortality of the Florida manatee Trichechus manatus latirostris accounts for 24% of all deaths from 1974 to 2006. Of these, the proportion of deaths due to impact accounts for 66% of all watercraft fatalities. To establish safe boat speeds for manatee protection, an estimate of the material properties of their bone is needed to quantify the biomechanical effects of boat strikes on manatees. Manatee ribs are unique in that they are pachyostotic. Machined specimens from ribs were tested in three point flexure. Strength, modulus, work of fracture and fracture toughness were determined for three size classes, by sex. The mean flexural strength ranged from 62 to 160 MPa, elastic modulus from 4 to 18 GPa and work of fracture from 3 to 6 MJ m−3. Fractographic analysis was used to calculate toughness, which averaged 1.4–2.9 MPa m1/2. The results show that manatee bone material is less strong and tough than other mammalian bone. Although the bone increases in static strength as the animals grow, it is not able to absorb more energy. In fact, the ability to absorb impact energy appears to decline with increasing size in animals over 265 cm body length. This decline is due in part to the bone's high density and mineral content. There was little change in mineral content with size, suggesting that material properties are likely correlated with bone quantity. There were no differences in mechanical variables between the sexes. The pachyostotic nature of the bone, which makes the manatee well adapted to its environment, also leaves it highly susceptible to fatal injuries from boats.

Morphological Changes in the Atlantic Bottlenose Dolphin (Tursiops truncatus) Adrenal Gland Associated with Chronic Stress

Beach-stranded Atlantic bottlenose dolphins (n=68) were categorized as either "acutely stressed" (if they died from net entanglement, boat strike, or acute infection; 31 animals) or "chronically stressed" (if they suffered from or died as a result of long-term disease or debilitating injury; 37 animals). No significant differences in mass between the right and left adrenal glands were found within each category. However, the average gland mass (AGM), based on the right and left glands together, was 5.2g for acutely stressed animals and 11.01 g for chronically stressed animals (P<0.001). Significant differences were also found, in terms of the ratio of cross-sectional areas of the cortex to medulla, between acutely stressed (ratio 1.22) and chronically stressed (ratio 1.63) animals (P=0.027). Adrenal glands of acutely stressed animals consisted of 48% cortex, 41% medulla, and 11% other tissue elements (connective tissue, blood vessels and gland capsule), whereas the corresponding figures for chronically stressed animals were 53%, 36%, and 11%. The mean estimated mass values for cortex, medulla and other tissue were, for acutely stressed animals, 2.36, 1.9, and 0.54, respectively, whereas for chronically stressed animals the corresponding figures were 6.06, 4.04, and 1.29 (P<0.001 for each of the three comparisons). Overstaining with haematoxylin (HEM) and immunohistochemical labelling (IHC) of the enzyme phenylethanolamine N-methyl transferase (which converts norepinephrine to epinephrine) were used to determine the percentage of epinephrine-producing cells in relation to the overall cross-sectional area of the adrenal gland. The percentage values in acutely as compared with chronically stressed dolphins were 6.7% and 15.93%, respectively (P=0.021). The results therefore suggest that in bottlenose dolphins chronic stress results in increases in (1) adrenal mass, (2) cortex to medulla ratio, and (3) epinephrine-producing cells within the medulla, giving rise to an increase in the thickness of the medullary band.

Assessing the risk of boat strike on Dugongs Dugong dugon at Burrum Heads, Queensland, Australia

The risk of mortality due to boat strike is increasingly being recognized as an important management issue for marine wildlife, including Dugongs Dugong dugon. Ameliorating the effects of boat strike requires assessment of how that risk varies over the management area. This is dependent on the distribution and movements of both Dugongs and boats and on the physical characteristics of the area, particularly depth. In this study we assess these features for a small community that is dependent on tourism centred around recreational fishing and which is home to a regionally significant Dugong population. During one of the most popular holiday times, boats accessing the favoured fishing site pass directly through the core area of Dugong activity. Our data show that boat strike risk to Dugongs can be lowered significantly with minimal imposition on boaters. Boaters can avoid the area of highest risk by travelling around it in deeper water. However, this straightforward solution is only possible because of the restricted spatial scale of Dugong activity and the proximity of a deepwater channel enabling boaters to easily avoid shallow areas where boat strike risk is highest.