Protected Species

PIFSC is actively engaged in research to support the conservation of sea turtles and marine mammals in the Pacific Islands Region. Studies conducted by Center scientists support management actions of NOAA and partner agencies under provisions of the U.S. Endangered Species Act and Marine Mammal Protection Act, including recovery plans and take reduction plans. Center biologists conduct population monitoring and other research on threatened and endangered populations of sea turtles and the endangered Hawaiian monk seal. Other PIFSC researchers monitor and assess populations of cetaceans across the Region, in collaboration with the Southwest Fisheries Science Center. During 2011, progress was noted in several areas:

Are Dynamics of Sea Turtle Populations Driven by Climate?

Current strategies to rebuild diminished sea turtle populations focus on causes of decline that are readily apparent and directly amenable to human intervention; for example, restoring degraded habitat; preventing loss of eggs, hatchlings and adult females on nesting beaches; and reducing mortality of turtles caused by fishing and marine debris. The premise is that these anthropogenic factors are the main determinants of sea turtle numbers. Recent research at PIFSC has challenged that perception by showing that for loggerhead turtles in the North Pacific and Northwest Atlantic, trajectories of abundance may be dictated largely by variations in climate.

In the North Pacific, juvenile loggerheads feed along edges of cyclonic (c) and anticyclonic (d) eddies where their prey are 
                   concentrated. The occurrence of these features in the turtles' oceanic habitat is part of the climatic variability measured by 
                   the Pacific Decadal Oscillation.
In the North Pacific, juvenile loggerheads feed along edges of cyclonic (c) and anticyclonic (d) eddies where their prey are concentrated. The occurrence of these features in the turtles' oceanic habitat is part of the climatic variability measured by the Pacific Decadal Oscillation.

The research was conducted by a PIFSC mathematical ecologist and a colleague from the University of Ioannina in Greece. They began their study by analyzing data collected on loggerhead nesting beaches in Japan and Florida. Loggerheads born on these beaches seed the populations in the North Pacific and Northeast Atlantic, respectively. Beach counts of nesters or nests are the primary source of information on loggerhead abundance, and trends in these counts over time are used to monitor population status. The number of females coming ashore to nest in a given year is dependent on two variables: (1) the unknown number of adult females in the population, i.e., all females recruited as juveniles in previous years that are mature and still alive, and (2) the probability that an adult female will nest in the current year. The research team postulated that each of these components is affected by certain climate conditions.

In the case of adult female loggerheads, current abundance depends partly on the fraction of post-hatchling turtles that survived their critical juvenile pelagic phase years earlier, and the team suggested that in the North Pacific this survival is tied to climate conditions measured by the Pacific Decadal Oscillation (PDO) index. The PDO index captures phase shifts in average North Pacific sea surface temperature north of 20° N and is seen as a proxy for survival of juvenile loggerheads foraging in the North Pacific. In other studies, the PDO has been correlated with biological productivity in northeast Pacific marine ecosystems. As for nesting probability, the team suggested that an adult female loggerhead's readiness to lay eggs was directly related to sea surface temperature in her foraging grounds during the winter months prior to the nesting season.

Based on these notions, the team assembled time series of the PDO index and winter SST and used them as predictors in a linear model of annual Japan loggerhead nest counts. The best-fitting model showed that relatively high nest counts were strongly associated with higher values of the PDO index 25 years earlier (the lag accounts for the years required for a female to reach maturity) and warmer SST in the preceding winter. Low nest counts were associated with lower PDO values and cooler winter SST. The full model, with both lagged PDO index and winter SST as predictors, explained 66% of the interannual variation in Japan loggerhead nest counts during the study period. In a similar model for Northwest Atlantic loggerheads, using the Atlantic Multidecadal Oscillation (with a 31-year lag) and winter SST as predictors, the combined model accounted for 77% of variation in loggerhead counts on Florida nesting beaches. Impressively, the models captured major features of nesting variability at both decadal and interannual scales, even at a local scale on beaches where most nesting occurs.

Although environmental conditions are well known to affect turtles, (e.g., dependence of hatchling sex ratio on nesting beach temperature), effects of climate and environment have largely been ignored in current approaches to sea turtle assessment. Human-caused mortality is usually viewed as the main driver of turtle population dynamics. Moreover, the abundance of nesters is assumed to be the key determinant of future recruitment. Clearly, anthropogenic factors are an important determinant of loggerhead abundance, but the fact that the climate-based models for North Pacific and Northeastern Atlantic loggerheads explained about 70% of year-to-year variation in nest counts, and that a high proportion of the variation was linked to climate-based proxies for recruitment success strongly suggests that a broader viewpoint is needed in sea turtle assessment and conservation.

The sea turtle research was published in 2011 in the peer-reviewed, public access journal PLos ONE [4].

Divergence of Regional Trends in Abundance of Hawaiian Monk Seals Alters their Distribution within the Archipelago

Models of Hawaiian monk seal abundance predict a steady decline in the Northwestern Hawaiian Islands and a concurrent increase in 
                   the main Hawaiian Islands. By 2024, equal numbers of seals are expected to occur in each part of the archipelago.
Models of Hawaiian monk seal abundance predict a steady decline in the Northwestern Hawaiian Islands and a concurrent increase in the main Hawaiian Islands. By 2024, equal numbers of seals are expected to occur in each part of the archipelago.

One of NOAA's major conservation goals is to reverse the decline of Hawaiian monk seals. The embattled species numbers about 1100 animals and is falling each year by 4%. If this rate of attrition were to persist, the population would be cut in half every 17 years and essentially vanish by the end of the century. To provide the scientific foundation for monk seal recovery, PIFSC has monitored and studied seals each summer at the major breeding locations in the remote Northwestern Hawaiian Islands (French Frigate Shoals, Laysan Island, Lisianski Island, Pearl and Hermes Atoll, Midway Atoll, and Kure Atoll), where most of the seals live. Biologists observe and record the number of seals present at each breeding site, paying particular attention to newborn seals. Unique markings on the pelage enable researchers to identify individual seals each time they are encountered and trace their history.

Data collected since the early 1980s show that the population of monk seals in the Northwestern Hawaiian Islands is decreasing steadily due to several causes, but primarily from low survival of juvenile seals. At French Frigate Shoals, for example, mortality of seal pups due to shark predation has been particularly severe. Vulnerability to predation is increased for many pups by a low weight at weaning, a condition linked to lack of success in foraging by their mothers.

In contrast to the Northwestern Hawaiian Islands, the main Hawaiian Islands have seen an upswing in seal sightings and documented activity, including the birth of several pups. But little is known about this much smaller segment of the population. So in 2008, a team of PIFSC scientists also surveyed seals in the main Hawaiian Islands, assisted by partner agencies and nongovernmental volunteers. Seal sightings on Oahu, Kauai and the other accessible islands were documented and when feasible, the seal's identity and biological characteristics were established. At the privately owned island of Niihau and nearby Lehua Rock, seals were counted and photographed from the air using a U.S. Coast Guard helicopter. After analyzing the survey data, the PIFSC team estimated that a minimum of 153 seals resided in the main Hawaiian Islands. The team also calculated that the main Hawaiian Island seals have higher survival than seals in the Northwestern Hawaiian Islands. In particular, weaned pups in the main Hawaiian Islands have a 77% chance of reaching their first birthday compared with only 20% for pups in the Northwestern Hawaiian Islands.

Although estimates of the current population size indicate that only 14% of Hawaiian monk seals live in the main Hawaiian Islands, PIFSC scientists predict that the distribution of seals along the archipelago will change. The research team used a computer model to forecast the population size in the main Hawaiian Islands and at each of the Northwestern Hawaiian Island breeding sites. If present rates of seal reproduction and survival remain constant, the number of seals in the main Hawaiian Islands will increase while seals in the Northwestern Hawaiian Islands decline, with the two components reaching equal levels in about 2025. Thereafter, the majority of seals are predicted to reside in the main Hawaiian Islands.

This scenario is uncertain. The projections are based on simplifying assumptions and, in the main Hawaiian Islands, relatively meager data. Survival and other vital rates may well change over time. Optimistically, NOAA's attempts to increase pup survival in the Northwestern Hawaiian Islands may reverse the monk seal's decline there, but given the current age composition of the population, such a turnaround would take many years. Other factors at play in the Northwestern Hawaiian Islands, including changes in ocean productivity and sea level due to climate change, will affect the population also. In the main Hawaiian Islands, the seal population may continue to grow at its present vigorous pace, or it may encounter limits; the capacity of the main Hawaiian Islands to support a larger number of seals is unknown. In any event, significant challenges lie ahead for the seals and NOAA scientists and managers seeking ways to recover the population.

The PIFSC study of monk seal population trends was published in the January 2011 issue of Marine Mammal Science [5].

Surveys Confirm Wintering of Humpback Whales in the Northwestern Hawaiian Islands

The primary wintering grounds of humpback whales in the North Pacific are in the main Hawaiian Islands (MHI). The whale population has grown substantially in recent decades in the wake of a global ban on whaling. As a result, public awareness of humpback whales has increased and whales have been seen in more inshore waters of the MHI. Studies of the population's distribution have also reached out into the Northwestern Hawaiian Islands (NWHI) and in 2007, a scientist at the University of Hawaii Joint Institute for Marine and Atmospheric Research (JIMAR) affiliated with the NOAA PIFSC published evidence of humpback whales wintering in the NWHI. He also applied a spatial habitat model to estimate the potential NWHI winter habitat for the whales. A more recent study, based on more extensive surveys, found that humpback whales are common in the NWHI during winter months and confirmed that this region is an important wintering habitat for the population.

Humpback whales are common in waters of the main Hawaiian Islands during their winter breeding season. Recent research confirmed 
                   that the whales also winter in the Northwestern Hawaiian Islands.
Humpback whales are common in waters of the main Hawaiian Islands during their winter breeding season. Recent research confirmed that the whales also winter in the Northwestern Hawaiian Islands.

The recent research was led by a scientist from the Hawaii Institute of Marine Biology (HIMB) and colleagues from HIMB, JIMAR, and PIFSC. They deployed devices called ecological acoustic recorders (EARs) at 9 study sites throughout the Hawaiian Archipelago to record the occurrence of humpback whale song, an indicator of winter breeding activity. The EAR is a microprocessor-based autonomous instrument that samples and records sound in the surrounding water at pre-programmed intervals of time. The timing and abundance of song recorded at each of the EAR sites indicate that humpback whales were common in the NWHI from late December 2008 to mid-May 2009, closely following trends observed at Oahu in the MHI and strongly suggesting that the whales use the NWHI as a wintering area.

The findings of the research team were published in the peer-reviewed journal Marine Ecology Progress Series [6].