” These are extreme population swings that we did not anticipate to see in a big, long-lived species like gray whales,” Stewart said. “When the schedule of their prey in the Arctic is low, and the whales can not reach their feeding locations since of sea ice, the gray whale population experiences rapid and major shocks.”
Vulnerability of Gray Whales to Climate Change
” Even highly mobile, long-lived species such as gray whales are sensitive to climate change effects. When there are unexpected declines in the quality of prey, the population of gray whales is considerably impacted.”.
The findings were just published in the journal Science.
A gray whale breaching. Credit: NOAA Fisheries (Photo taken under permit).
Eastern North Pacific gray whales are among the couple of populations of large whales that have recovered to what may be similar numbers that existed prior to business whaling. As the population has approached levels near to what their Arctic feeding locations can support, they have most likely become more delicate to ecological conditions due to competitors for limited resources, Stewart stated.
The undesirable Arctic conditions that caused 2 die-offs in the 1980s and the 1990s were not long-term, and the population quickly rebounded as conditions improved.
” It ends up we didnt actually know what a healthy baleen whale population looks like when it isnt heavily diminished by human impacts,” he said. “Our presumption has actually typically been that these recovering populations would strike their environmental bring capabilities and remain more or less constant there. What were seeing is much more of a bumpy ride in response to highly variable and quickly altering ocean conditions.”.
Gray Whale Migration and Research.
Eastern North Pacific gray whales, which presently number about 14,500, move more than 12,000 miles each year along the Pacific Coast, from the warm waters off the coast of Baja California, Mexico, in the cold weather to the cold, productive waters of the Arctic to feed in the summertime months.
Researchers at the National Oceanic and Atmospheric Administration Southwest Fisheries Science Center in La Jolla, California, have been carrying out long-term population monitoring research studies of these whales given that the 1960s, tracking birth, abundance and death rates, and tracking body condition using aerial images. This substantial research study has actually made this population of gray whales the most closely studied big whale population on the world, supplying a special window into the population dynamics of the species.
A Southwest Fisheries Science Center researcher scans for gray whales during a survey as part of the long-term population monitoring research study. Credit: NOAA Fisheries.
” This research study shows the value of long-term information in understanding not just the species under study but also the environment it depends upon,” said Dave Weller, director of the Southwest Fisheries Science Centers Marine Mammal and Turtle Division. “When we started gathering information on gray whales in 1967, little bit did we realize the important role they would play in comprehending the effects of climate change on an iconic guard types in the Pacific. This research would not have actually been possible without our reputable long-term record.”.
Preservation Success and Ongoing Challenges.
The eastern North Pacific gray whale population, which was hunted to near termination before a whaling moratorium was enacted, has been deemed a preservation success story due to the fact that of the populations fast healing in the post-whaling period.
In 2019, when a high variety of gray whale strandings began occurring along the Pacific coast, Stewart, a scientist at the Southwest Fisheries Science Center at the time, started looking more carefully at the long-term information to see if he might discover more about what might be driving the unusual death event.
By integrating the long-lasting data sets on the gray whale population with extensive ecological data from the Arctic, Stewart and his collaborators figured out that the 2 “Unusual Mortality Events” declared by NOAA in 1999 and 2019 were tied to both sea ice levels in the Arctic and the biomass of seafloor-living shellfishes that gray whales target for food.
Stewart likewise identified a third die-off in the 1980s that followed a similar pattern however was not connected with higher numbers of strandings, likely due to lower reporting rates of stranded whales prior to the 1990s.
The researchers found that years with less summertime sea ice in the gray whales Arctic feeding areas provided increased foraging chances that benefited the population. However, in the long term, reducing sea ice cover, an outcome of fast and accelerating climate change, probably will not be advantageous to gray whales.
Benthic amphipods, the calorie-rich victim that gray whales choose, are likewise conscious sea ice cover. Algae that grow beneath sea ice sink to the seafloor, improving the amphipod population. Less ice results in less algae reaching the seafloor, warmer water that prefers smaller benthic crustaceans and faster currents that minimize environment for gray whales favored prey.
” With less ice, you get less algae, which is even worse for the gray whale victim,” Stewart said. “All of these elements are converging to minimize the quality and schedule of the food they depend on.”.
For the gray whales, less victim availability ultimately causes die-offs. The most current event is still thought about ongoing and has actually continued considerably longer than the two earlier occasions.
” We remain in uncharted territory now. The 2 previous events, regardless of being considerable and remarkable, just lasted a couple of years,” Stewart stated. “The most current death occasion has slowed and there are indications things are reversing, but the population has actually continued to decline. One factor it might be dragging on is the environment modification element, which is contributing to a long-term pattern of lower-quality prey.”.
Gray Whales and the Future.
Gray whales have endured numerous thousands of years of environmental modification and have adapted over that time to changing conditions, making termination due to environment modification unlikely, Stewart said.
” I wouldnt say there is a risk of losing gray whales due to environment modification,” he said. “But we require to think seriously about what these modifications might indicate in the future. An Arctic Ocean that has actually warmed substantially might not be able to support 25,000 gray whales like it has in the current past.”.
Recommendation: “Boom-bust cycles in gray whales associated with vibrant and changing Arctic conditions” 12 October 2023, Science.DOI: 10.1126/ science.adi1847.
Coauthors of the study include Trevor W. Joyce of Ocean Associates; John Durban of the Marine Mammal Institute and Sealife Response, Rehabilitation and Research; John Calambokidis of Cascadia Research Collective; Deborah Fauquier of the NOAA Fisheries Office of Protected Resources; Holly Fearnbach of SR3; Jacqueline Grebmeier of the University of Maryland Center for Environmental Science; Morgan Lynn, Wayne Perriman of the Southwest Fisheries Science Center, NOAA Fisheries; Manfredi Manizza of the Scripps Institution of Oceanography, University of California, San Diego; and Tim Tinker of Nhydra Consulting and University of California, Santa Cruz.
The Marine Mammal Institute becomes part of Oregon States College of Agricultural Sciences and is based at Hatfield Marine Science Center in Newport.
Gray whales moving south in between their summer season feeding grounds in the Arctic and wintering lagoons in Mexico. “When we began collecting data on gray whales in 1967, bit did we recognize the essential function they would play in understanding the effects of climate modification on a renowned sentinel species in the Pacific. Less ice leads to less algae reaching the seafloor, warmer water that favors smaller sized benthic shellfishes and faster currents that minimize environment for gray whales preferred victim.
” I would not say there is a threat of losing gray whales due to climate change,” he said. An Arctic Ocean that has warmed considerably might not be able to support 25,000 gray whales like it has in the current past.”.
Gray whales migrating south in between their summer feeding premises in the Arctic and wintering lagoons in Mexico. Allow number 14097. Credit: NOAA Fisheries/SWFSC/MMTD.
Dynamic Arctic conditions have caused significant die-offs in gray whales given that the 1980s. In spite of their versatility, climate modification presents new challenges, affecting their prey and possibly future population sizes.
Dynamic and changing Arctic Ocean conditions likely caused three major mortality occasions in the eastern North Pacific gray whale population since the 1980s, a brand-new study has actually discovered.
During each of these die-offs, including one that started in 2019 and is ongoing, the gray whale population was reduced by approximately 25% over just a couple of years, said Joshua Stewart, an assistant professor with Oregon State Universitys Marine Mammal Institute and the research studys lead author.
