Chugach Transient Killer Whales

Chugach transients, Photo provided by Gulf Watch Alaska.

### Notable Individuals

AT1 "Eyak", AT2 "Marie", AT3 "Ewan", AT4 "Paddy", AT5 "Shadow", AT6 "Egagutak", AT7 "Kaj", AT8 "Totemof", AT9 "Chenega", AT10 "Mike", AT11 "Ripple Fin", AT12 "Lankard", AT13 "Holgate", AT14 "Eccles", AT15 "Moon", AT16 "Trident", AT17 "Aligo", AT18 "Iktua", AT19 "Berg", AT20 "Hermit", AT21 "Icy", AT22 "Gage"

## Conservation

### Threats

Post-reproductive stock, Exposure to toxic food sources

The **Chugach transients** also known as the **AT1 transients** are a small and functionally extinct population of mammal-eating killer whales ranging from Prince William Sound, Alaska to Kenai Fjords, Alaska.

## Population

The Chugach transients are studied by the North Gulf Oceanic Society which started formally in 1984, with the earliest known sightings being dated to 1978. They are genetically and socially distinct population from both the Gulf of Alaska transients and the West Coast transients (Biggs') proven by DNA analysis. They also have a unique set of acoustic calls, distinct from other killer whales in the region, and behaviours that sometimes made researchers wonder if they shared more in common with resident-aligned killer whales.
At the start of the study twenty-two individuals were recorded and assigned numerical identifications. Their names are:

* AT1 "Eyak"
* AT2 "Marie"
* AT3 "Ewan"
* AT4 "Paddy"
* AT5 "Shadow"
* AT6 "Egagutak"
* AT7 "Kaj"
* AT8 "Totemof"
* AT9 "Chenega"
* AT10 "Mike"
* AT11 "Ripple Fin"
* AT12 "Lankard"
* AT13 "Holgate"
* AT14 "Eccles"
* AT15 "Moon"
* AT16 "Trident"
* AT17 "Aligo"
* AT18 "Iktua"
* AT19 "Berg"
* AT20 "Hermit"
* AT21 "Icy"
* AT22 "Gage"

### Exxon Valdez oil spill

The first population census was conducted in 1984, with sightings reported either annually or bi-annually until 1988. During these years no deaths or new births were recorded into the population. However in 1989, the Exxon Valdez oil spill greatly effected the Chugach transient population. Photos within days of the spill showed members both of the AT1 transients and AB residents, another member of the Alaskan killer whale population, swimming within the spill zone. AT5 "Shadow", AT7 "Kaj", and AT8 "Totemof" were identified to have been whales that were sighted near the leaking Exxon Valdez. In 1989, the year of the spill, nine Chugach transients went missing, including the previously mentioned three. Two others were found deceased on shore in 1989 and 1990. One of these whales was visually identified as AT19 "Berg". One belief that caused this wave of deaths is the oil vapours would have caused near instant mortality amongst those exposed. The other is the transient's primary food source, harbor seals, were also exposed to the oil, becoming covered in the substance, so it is thought that this may have caused premature mortality amongst the population.
### Current day

In subsequent years, the Chugach population continued to decline. In the early 2000s the population lost four more whales: AT1 "Eyak" in 2000, AT13 "Holgate" and AT17 "Aligo" (missing since 2002, one of which believed to be a body washed ashore the same year), and then AT14 "Eccles" in 2003. Since 2003, seven transients remain and as of 2021 all of them are confimed alive. Sightings in 2022 and 2023 have occured, however, no official statement regarding the seven has been made to confirm their individual statuses. Research has concluded that the remaining members are the last generation of the Chugach transients as those that remain are post-reproductive, with the youngest member being 39 (AT10 "Mike") and the eldest being 57 (AT9 "Chenga").
## Population range

Almost akin to the range of resident populations, the Chugach transients are only observed in the region between Prince William Sound, Alaska to Kenai Fjords, Alaska. Over the course of the study, this population have reliably been studied within this range and haven't been observed outside of it.
## Identification

Killer whales of the Chugach transient population are large with traits common amongst other transient groups. They have smooth, closed saddle patches. These saddle patches also showcase rakemarks, sometimes very noticeable as they are deep. Their dorsal fins are pointed at the tips and many of the members of this group have wide fins and are frequently notched. Chugach transients have relatively average sized eye patches that slope upwards in a subtle manner.
The last remaining members of the Chugach transients are included in their own identification catalogue, hosted by the North Gulf Oceanic Society, which can be found on their website. A previous revision of the catalogue listed twenty-one members with other Alaskan pods in an older physical copy from 1991.
## See also

* Population timeline

### Photo-identification catalogue

* **1991 edition featuring all 22 AT1 transients**
* **2021 edition featuring the remaining 7 AT1 transients**

## References

1. ↑ 1.0 1.1 Killer Whale *(Orcinus orca)*: AT1 Transient Stock
2. ↑ 2.0 2.1 Into great silence: a memoir of discovery and loss among vanishing Orcas (Saulitis, Eva. 2013)
3. ↑ 3.0 3.1 Ongoing population-level impactons on killer whales *Orcinus orca* following the 'Exxon Valdez' oil spill in Prince William Sound, Alaska
4. ↑ North Gulf Oceanic Society (Facebook)
5. ↑ North Gulf Oceanic Society