Noteworthy (formerly Hot Topics) (pdf)
We include information here that is relevant to ecosystem considerations of fisheries managers, but does not fit our typical indicator format. Information included here is often new or a one-time event.
Seabird Mortality Event: Middleton Island July 2021
In mid-July 2021, a large number of sick and dying seabirds were observed on Middleton Island, south of Prince William Sound (PWS) in the Gulf of Alaska. During the 10-day period, 250 Black- legged Kittiwakes Rissa tridactyla, 70 Glaucous-winged Gulls Larus glaucescens and 2 Herring Gulls Larus argentatus were found dead, and 220 kittiwakes and 19 Glaucous-winged Gulls were observed sick. Kittiwakes and Glaucous-winged Gulls are among six seabird species monitored by the Institute for Seabird Research and Conservation on Middleton Island. Affected birds exhibited neurological signs and abnormal behavior. At first, sick birds lost their ability to fly, then gradually lost their ability to move, and all died within ∼ 5 days of the first signs of sickness. This mortality event was detected and monitored by seabird researchers already on Middleton Island conducting ecology and disease studies, and large numbers of carcasses, blood, feces, and food samples were collected from all monitored seabird species. A coordinated response to determine the cause of this die-off was launched by scientists at the Institute for Seabird Research and Conservation, the University of Alaska Fairbanks, the University of Alaska Anchorage, McGill University (Quebec, Canada), Frostburg State University, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey Alaska Science Center and National Wildlife Health Center. The University of Alaska INBRE program provided funding for the collection, shipment, and initial molecular analyses of bird samples and carcasses, which allowed us to advance the investigation of potential causes of the die-off. The National Oceanographic and Atmospheric Administration (NOAA) Alaska Sea Grant provided additional funding to assist with transportation of personnel to participate in sample processing and training.
The cause of death was not immediately clear. Many sick and deceased birds were emaciated or in poor condition, but tested negative for highly pathogenic avian influenza, and the biotoxins saxitoxin (STX) and domoic acid (Table 1). Blue mussels, plankton, and forage fish samples from recent kittiwake foraging locations near the outer islands of PWS (Figures 3 and 4) also tested negative for STX, as did blue mussels and feces from both presumably healthy and sick kittiwakes collected at Middleton during the die-off (Table 1). Next generation sequencing (metagenomics)
analysis of RNA samples collected from sick and dead kittiwakes indicated the presence of Clostridia spp. in all birds, and significant reads in cloacal swabs classifiable as C. botulinum (n=2/12 birds, 17% prevalence; Table 2). Clostridia are a group of bacterial species that can produce botulinum neurotoxins, which can cause botulism. Further analysis of blood from two deceased kittiwakes revealed a positive bioassay test for (avian) botulinum toxin type C in one bird and a suspected positive result for the other; both birds tested negative for botulinum toxin type E, the botulinum toxin type that has been found to cause botulism in humans in the Arctic. Researchers plan to conduct additional tests to determine whether botulinum toxin type C was the culprit of the die-off and to investigate sources of this neurotoxin. This appears to be the first verified case of botulinum toxin type C in Alaska. Botulism can cause large die-offs of waterbirds, but botulinum toxin type C has not been associated with disease in humans.
Figure 3: GPS foraging tracks (n=16) of male, chick-rearing Black-legged Kittiwakes originating from Middleton Island from July 6-July 15, 2021 (prior to the seabird mortality event). Colors represent each bird’s speed, with lowest value (red, 0 km h-1) representing no movement and assumed foraging. Data provided by the Institute for Seabird Research and Conservation.
Table 1: Number of individuals that tested negative for highly pathogenic avian influenza (HPAI), and below detection for the biotoxins saxitoxin (STX) and domoic acid (DA).1Pooled sample.
Figure 4: GPS foraging tracks of chick-rearing Black-legged Kittiwakes (n=15) originating from Mid- dleton Island from July 16-July 20, 2021 (during the seabird mortality event). Colors represent each bird’s speed, with lowest value (red, 0 km h-1) representing no movement and assumed foraging. Data provided by the Institute for Seabird Research and Conservation.
Table 2: Metagenomics classification of Clostridia spp. reads from RNA-seq on cloacal swabs from black- legged Kittiwakes from Middleton Island, Alaska, including C. botulinum (n=2 of 12, 17% prevalence).
The ecological implications of this seabird mortality event are still being explored. Seabird die-offs in Alaska have increased in magnitude, duration, and frequency since 2015. Most seabird die- offs have been attributed to starvation from a presumed lack of available food, however, this die-off appears likely to have been caused by a disease. The potential origin of the botulinum toxin remains unknown, but fresh or brackish water pools that contain dipteran populations (that can be part of the maggot-cycle) on Middleton Island in which kittiwakes often bathe are potential sources. Diet and reproductive data of kittiwakes collected during the time of the die-off on Middleton Island do not show indication of poor foraging conditions that might have contributed to changes in foraging behavior (i.e., feeding in the brackish pools of Middleton Island). The diet composition and GPS tracking data indicate the kittiwakes were feeding more nearshore, closer to PWS, continuing a trend observed since the 2014–2016 marine heatwave (Figures 3 and 4) (see Seabird Synthesis in Report, p.94). While extended foraging trips, and reduced capelin in kittiwake diets may contribute to a level of foraging stress, as shown in supplemental feeding experiments, other 2021 indicators, such as reproductive success and timing were close to the ∼ 40 year average (see Seabird Synthesis in Report, p.152). If the cause of this event is determined to be botulism, this event and subsequent mortality could be a harbinger of more such events as the distribution of naturally occurring toxins expands northward alongside warming oceans and changing weather patterns.
Contributed by Sarah Schoen1, Fred Tremblay2,3, Naomi Bargmann1, Barb Bodenstein4, Eric Bortz5, Doug Causey5, Jack Chen6,7, Scott Hatch2, Robb Kaler8, Alexander Kitaysky6, John Piatt1, Matthew Redlinger5, Valerie Shearn-Bochsler4, Kate Sheehan9, Matthew Smith1, Caroline Van Hemert1, Shannon Whelan2, and Alexis Will6
1 U.S. Geological Survey Alaska Science Center, Anchorage, AK
2 Institute for Seabird Research and Conservation, Anchorage, AK
3 McGill University, Montreal, QC
4 U.S. Geological Survey National Wildlife Health Center, Madison, WI
5 University of Alaska Anchorage, Anchorage, AK
6 University of Alaska Fairbanks, Fairbanks, AK
7 Alaska State Virology Laboratory, Fairbanks, AK
8 U.S. Fish and Wildlife Service, Anchorage, AK
9 Frostburg State University, Frostburg, MD
North Pacific Right Whale Sightings
Four unique North Pacific right whales (Eubalaena japonica), two during each of two sightings, were sighted during a large whale survey (PacMAPPS) near Kodiak Island (see Crance in this Report, p.168). This endangered population is estimated to consist of approximately 30 whales and this is more sightings of these North Pacific right whales than occurred on any other cetacean survey in the GOA. Two whales were sighted in Barnabas Trough (sighted 21 Aug), and two whales were sighted near Trinity Islands (sighted 24 Aug). Of the four animals, two were confirmed new and added to the catalog. One animal (a male from the Trinity Islands sighting) was first sighted in 2006 in Barnabas Trough, and this is the first re-sighting of that animal, only about 100 nm from his first sighting location. One animal (from the Barnabas sighting) was first sighted near Haida Gwaii in June of this year by DFO Canada. This is the first time we’ve matched an animal from Haida Gwaii to any other location.
Sightings of right whales in the GOA are even more rare than Bering Sea sightings. It is unknown whether the Bering and the GOA right whales might be two separate subpopulations or part of the same population. We have yet to match a whale from the Bering Sea to the GOA. Both right whale sightings occurred along Albatross Bank, an area known for being highly productive and having high concentrations of zooplankton. This area was identified as a Biologically Important Area for feeding for North Pacific right whales in 2015 (Ferguson et al., 2018). There was feces in the water and behavior associated with feeding (e.g., expelling water from the mouth) during both sightings, providing further evidence that this area is important habitat for right whales. It is difficult to interpret the identification of two new whales in terms of population status or trends, since re-sightings (and sightings in general) are so infrequent. Dedicated marine mammal visual surveys are crucial and provide much better information on cetacean distribution, density, and abundance than just opportunistic observations. Two of the right whales would not have been sighted without the 25x big-eye binoculars used during these surveys - they were too far from the trackline to have been seen with handheld 7x50 binoculars.