Masao Amano

Stroke frequency, but not swimming speed, is related to body size in free-ranging seabirds, pinnipeds and cetaceans

It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of animals ranging from 0.5 kg seabirds to 30 000 kg sperm whales using animal-borne accelerometers. Dominant stroke cycle frequencies of swimming specialist seabirds and marine mammals were proportional to mass−0.29 (R2=0.99, n=17 groups), while propulsive swimming speeds of 1–2 m s−1 were independent of body size. This scaling relationship, obtained from breath-hold divers expected to swim optimally to conserve oxygen, does not agree with recent theoretical predictions for optimal swimming. Seabirds that use their wings for both swimming and flying stroked at a lower frequency than other swimming specialists of the same size, suggesting a morphological trade-off with wing size and stroke frequency representing a compromise. In contrast, foot-propelled diving birds such as shags had similar stroke frequencies as other swimming specialists. These results suggest that muscle characteristics may constrain swimming during cruising travel, with convergence among diving specialists in the proportions and contraction rates of propulsive muscles.

Organohalogen contaminants in striped dolphins (Stenella coeruleoalba) from Japan: Present contamination status, body distribution and temporal trends (1978–2003)

Organohalogen contaminants including PCBs, DDTs, CHLs, HCHs, HCB, PBDEs and HBCDs were determined in striped dolphins (Stenella coeruleoalba) found stranded at Gogo-shima (n=6, 2003) and collected from Taiji (n=15, 1978-1992) in Japan. All target compounds were significantly detected in all the specimens, indicating ubiquitous contamination of oceanic cetaceans in northwest Pacific Ocean. Examination of body distribution of organohalogens in the six specimens from Gogo-shima showed no significant difference in concentrations among the analyzed tissues, except for brain, which had lower levels possibly due to the existence of blood-brain barrier. For evaluating temporal trends, archived blubber samples of adult male stripped dolphins collected in 1978, 1979, 1986 and 1992 were analyzed. Concentrations of PCBs, DDTs and HCHs did not change significantly during 1978-2003. In contrast, remarkable increasing trends of PBDEs and HBCDs were observed, suggesting growing consumption in Japan and surrounding countries in recent years.

Toxicokinetics of PCDD, PCDF, and coplanar PCB congeners in Baikal seals, Pusa sibirica: age-related accumulation, maternal transfer, and hepatic sequestration.

To assess the toxicokinetic behavior and potential toxicity of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) in Baikal seals, congener-specific levels and tissue distribution were evaluated in the liver and blubber, and the effects of biological factors including sex and growth were assessed. Total 2,3,7,8-TCDD toxic equivalents (TEQs) were in the range of 210-920 pgTEQ/g fat wt (180-800 pgTEQ/g wet wt) in the blubber and 290-7800 pgTEQ/g fat wt (10-570 pgTEQ/wet wt) in the liver. Non-ortho coplanar PCB126 was the most TEQ-contributed congener accounting for 37-59% of the total TEQs in the liver. From the unique congener profiles, weak metabolic properties of Baikal seals for 2,3,7,8-TCDF and 1,2,3,7,8-P5CDF are suggested. Concentrations of most congeners linearly increased with age in male seals, whereas in adult females the levels revealed an age-related decline. The increasing and declining rates were congener-specific. Maternal transfer rates of 5 representative congeners from adult female to pup through lactation, which was estimated from male-female differences in the body burden, was 1.1 ngTEQ/kg/day for the first pup and decreased with every lactational epoch. The liver-blubber distribution of 1,2,3,4,7,8-H6CDD, 1,2,3,6,7,8-H6CDD, PCB81, PCB126, and PCB169 was dependent on the hepatic total TEQ, indicating hepatic sequestration by induced cytochrome P450 (CYP). These results indicate that congener profile in Baikal seals is governed by complex factors including sex, tissue concentration, binding to CYP, and rates of absorption and metabolism/excretion.

Scaling of swim speed in breath-hold divers.

1. Breath-hold divers are widely assumed to descend and ascend at the speed that minimizes energy expenditure per distance travelled (the cost of transport (COT)) to maximize foraging duration at depth. However, measuring COT with captive animals is difficult, and empirical support for this hypothesis is sparse. 2. We examined the scaling relationship of swim speed in free-ranging diving birds, mammals and turtles (37 species; mass range, 0·5-90,000 kg) with phylogenetically informed statistical methods and derived the theoretical prediction for the allometric exponent under the COT hypothesis by constructing a biomechanical model. 3. Swim speed significantly increased with mass, despite considerable variations around the scaling line. The allometric exponent (0·09) was statistically consistent with the theoretical prediction (0·05) of the COT hypothesis. 4. Our finding suggests a previously unrecognized advantage of size in divers: larger animals swim faster and thus could travel longer distance, search larger volume of water for prey and exploit a greater range of depths during a given dive duration. 5. Furthermore, as predicted from the model, endotherms (birds and mammals) swam faster than ectotherms (turtles) for their size, suggesting that metabolic power production limits swim speed. Among endotherms, birds swam faster than mammals, which cannot be explained by the model. Reynolds numbers of small birds (<2 kg) were close to the lower limit of turbulent flow (∼ 3 × 10(5) ), and they swam fast possibly to avoid the increased drag associated with flow transition.

Finless porpoise: Neophocaena phocaenoides

Publisher Summary The finless porpoise is a small phocoenid cetacean lacking a dorsal fin. The species has a rounded head without an apparent beak. Its color is uniformly dark to pale gray and somewhat lighter on the ventral side. The teeth are spatulate in shape like those of most other porpoises of the family phocoenidae. Finless porpoises inhabit shallow coastal waters and some rivers in the Indo-Pacific region. Finless porpoises prefer the mangrove zone in tropical waters. They are also found in estuaries and large river systems such as the Indus, Ganges, and Yangtze Rivers. Finless porpoises rarely form large schools and are usually found in pairs. Mother and calf or an adult pair is the basic social unit in finless porpoises. Finless porpoises usually swim quietly and do not leap or make splashes. They tend to avoid vessels and do not bow ride.

Contamination status of POPs and BFRs and relationship with parasitic infection in finless porpoises (Neophocaena phocaenoides) from Seto Inland Sea and Omura Bay, Japan

Contamination status of brominated flame retardants (BFRs) and persistent organic pollutants (POPs) in blubber of finless porpoises (Neophocaena phocaenoides) stranded along the coasts of Seto Inland Sea and Omura Bay in Japan were investigated. Levels of PCBs, DDTs and CHLs were significantly higher than those of HCHs, HCB, PBDEs and HBCDs. Concentrations of PBDEs and HBCDs, as well as organochlorine compounds in males increased with body length (p<0.05). Among 14 PBDE congeners analyzed, BDE-47 was the predominant, which is similar to those generally reported in biota. PBDEs, HBCDs and PCBs showed no obvious temporal trend in concentrations during the study period, suggesting continuous environmental release of these chemicals. On the other hand, levels of DDT, CHLs and HCHs have decreased. Concentrations of PCBs in liver trematode infected individuals were significantly higher than those in not infected individuals, implying there could be a relationship between contaminant levels and parasitic infection.

The Role of Canine Distemper Virus and Persistent Organic Pollutants in Mortality Patterns of Caspian Seals (Pusa caspica)

Persistent organic pollutants are a concern for species occupying high trophic levels since they can cause immunosuppression and impair reproduction. Mass mortalities due to canine distemper virus (CDV) occurred in Caspian seals (Pusa caspica), in spring of 1997, 2000 and 2001, but the potential role of organochlorine exposure in these epizootics remains undetermined. Here we integrate Caspian seal mortality data spanning 1971–2008, with data on age, body condition, pathology and blubber organochlorine concentration for carcases stranded between 1997 and 2002. We test the hypothesis that summed PCB and DDT concentrations contributed to CDV associated mortality during epizootics. We show that age is the primary factor explaining variation in blubber organochlorine concentrations, and that organochlorine burden, age, sex, and body condition do not account for CDV infection status (positive/negative) of animals dying in epizootics. Most animals (57%, n = 67) had PCB concentrations below proposed thresholds for toxic effects in marine mammals (17 µg/g lipid weight), and only 3 of 67 animals had predicted TEQ values exceeding levels seen to be associated with immune suppression in harbour seals (200 pg/g lipid weight). Mean organonchlorine levels were higher in CDV-negative animals indicating that organochlorines did not contribute significantly to CDV mortality in epizootics. Mortality monitoring in Azerbaijan 1971–2008 revealed bi-annual stranding peaks in late spring, following the annual moult and during autumn migrations northwards. Mortality peaks comparable to epizootic years were also recorded in the 1970s–1980s, consistent with previous undocumented CDV outbreaks. Gompertz growth curves show that Caspian seals achieve an asymptotic standard body length of 126–129 cm (n = 111). Males may continue to grow slowly throughout life. Mortality during epizootics may exceed the potential biological removal level (PBR) for the population, but the low frequency of epizootics suggest they are of secondary importance compared to anthropogenic sources of mortality such as fishing by-catch.

Post-conflict affiliation as conflict management in captive bottlenose dolphins (Tursiops truncatus).

Post-conflict affiliation between former opponents or between one of the former opponents and bystanders might have the function of conflict management, which reduces the costs associated with aggressions. One of the suggested functions of post-conflict affiliation is decreased renewed aggressions directed from aggressors to victims. However, the effect of post-conflict affiliation on renewed aggressions by victims has not been investigated. We examined whether post-conflict affiliations decreased the number of renewed aggressions initiated by winners or losers in captive bottlenose dolphins. Both winners and losers initiated renewed aggressions. However, these aggressions decreased after post-conflict affiliation between former opponents, initiated by bystanders to winners, initiated by losers to bystanders, and initiated by bystanders to losers. Post-conflict affiliation between former opponents is suggested to function as reconciliation. Post–conflict affiliation initiated by losers to bystanders is suggested to function as the protection of losers. Post-conflict affiliations initiated by bystanders to one of former opponents are suggested to function as both appeasement and protection of the opponent who affiliates with bystanders.

Age determination and growth of Baikal seals (Phoca sibirica)

Abstract The ages of 75 Baikal seals (Phoca sibirica) were determined in order to study the growth pattern of body length and body weight in this species. Longitudinal decalcified and stained sections of canine teeth were prepared, and growth layer groups (GLGs) in the dentine and cementum were counted. In those specimens with fewer than 10 GLGs, the GLG counts in dentine agreed well with those in cementum. However, in specimens with more than 10 GLGs, the cemental GLGs tended to exceed dentinal ones. Individuals of 4–5 years old were absent from the sample population, suggesting that the recorded mass mortality of Baikal seals in 1987–1988 (4–5 years before sampling) had affected the age composition. Growth of body length, body weight and core weight ceased at around 20 years of age. The growth pattern was similar to that of ringed seals (Phoca hispida), but differed from that of other Phoca species. Asymptotic body length and core weight were significantly different between sexes, but body weight was not. In the spring sampling period, female body weights tended to be heavier than those of males of the same body length, a feature attributed to the thicker blubber of females. Sexual dimorphism, and the large fluctuation in body weight and presence of secondary sexual characters reported in males, suggested the presence of intermale competition in the Baikal seal, presumably for access to females.

Swim Speed and Acceleration Measurements of Short-Finned Pilot Whales (Globicephala macrorhynchus) in Hawai'i

Cascadia Research Collective, 218 1/2 W. 4th Avenue, Olympia, WA 98501, USAOver the last few years, studies of top predators inmarine ecosystems have benefited from the use of bio-logging systems (Naito 2004; Rutz and Hays 2009). Forexample, researchers use these techniques to study ani-mal foraging tactics and diving physiology by analyzingacceleration (body angle and stroke), and parameterssuch as swim depth and swim speeds (e.g., Sato et al.2003, 2007; Sakamoto et al. 2009).Short-finned pilot whale (Globicephala macrorhynchus),a top predator, is found worldwide in tropical and warmtemperate waters. Mature males are from 4.5 to 7 m inlength and mature females are from 3.5 to 5 m in length(Bernard and Reilly 1999). Previous studies suggestedthey are foraging during deep dives which cannot beobserved visually. Their primary prey are squid and inHawai‘i they are known to make deep dives (600–800 m)during the day, but also spend considerable periods oftime shallow diving or surface resting during the day(Baird et al. 2003). Amano and Baird (1998) recordeddeep dives over 100 m off Japan. Soto et al. (2008)recorded sound, depth, and orientation from triaxialaccelerometers and magnetometers, and suggested preychasing behavior by analyzing vertical speed and soundemission during deep dives. For a better understandingof foraging tactics and diving physiology of this species,for example studying prey pursuit in a horizontal direc-tion, stroking patterns and body angle, or assessingbehavior by acceleration, we need to record accelerationand swim speed simultaneously. However, swim speedfor short-finned pilot whales has not yet been recorded.We used remotely deployed suction-cup tags formeasuring swim speed and acceleration of short-finnedpilot whales. The understanding of toothed whale be-havior has been advanced by using suction-cup attacheddata loggers (for a review see Hooker and Baird 2001).There are several types of suction-cup attached tag: oneattached with multiple suction-cups that fixed a datalogger in place (e.g., Soto et al. 2008), which with asingle suction-cup connected to a data logger with aflexible plastic tube (Baird et al. 2005), and one with asingle suction-cup that fixed a data logger in place.With removely-deployed tags, it is difficult to set thetag parallel to the water flow. Therefore it would behard to record swim speed using a propeller with amultiple suction-cup tag. A tag using a flexible plastictube cannot record acceleration caused by the animalprecisely because it is not fixed on the animal’s body.A tag fixed on a suction-cup has been demonstratedto record swim speed and acceleration simultaneouslyin previous studies (finless porpoises, Neophocaenaphocaenoides, Akamatsu et al. 2005; sperm whales,Physeter macrocephalus, Aoki 2008). The purpose ofour work was to determine whether this type of suction-cup tag is appropriate for studying swim speed andacceleration in short-finned pilot whales, and whetherit was possible to determine behavior types based onthe data collected.