|Halibut (chaatl) are an important food source for tribal members that can be harvested year-round. They are one of the most caught species by weight, surpassing even salmon. The size of halibut that could be caught was traditionally determined by the shape of the halibut hook—if the fish were too small, they couldn’t get the hook in their mouth, and if they were too large it would slip back out again. This allowed for strict control of which fish were getting caught, leaving the small ones to keep growing and the largest ones to keep breeding. Tribal members were particularly concerned about non-local users harvesting the wrong members of the population, with one HIA member stating, “leave those babies and those giants alone,” when talking about people on the docks with chicken sized halibut. With more sport and charter fishers coming from Juneau and other urban areas, the pressure on halibut is likely to increase in the future.|
THE AVERAGE SIZE OF HALIBUT IS LIKELY TO DECREASE BUT IT MAY OR MAY NOT ALL BE CLIMATE RELATED.
The length and size-at-age of halibut rose sharply from the 1920s through to the 1980s, but has been rapidly declining since then. While the exact drivers of that decline are still somewhat unknown, it is linked to environmental causes. Researchers also found that in years when fewer halibut were caught, the average size was larger. The average weight of a 20-year-old halibut has declined over 60 pounds from 1988 to 2013, dropping from 120 lbs. to 45 lbs. Field studies also show that while halibut can be found in waters of 3.8-11 C, they are most commonly found in temperatures of 5-7 C. There was also no relationship between the Pacific Decadal Oscillation, a year’s long pattern of climate variability that alters sea surface temperatures, and halibut size. This means that warming waters might not be the culprit for halibut getting smaller, and it may be a result of fishing practices or competition with other species. Regardless of the cause though, halibut are expected to continue getting smaller in the coming decades, meaning tribal members will have to catch more halibut and spend more fuel and time doing so to get the same amount of meat.
WARMER WATERS WILL CHANGE THE TIMING OF HALIBUT EGG DEVELOPMENT AND HATCHING AND INCREASE THE RISK OF DEAD ZONES.
The timing of when halibut lay eggs and how long it takes for them to develop depends heavily on the water temperatures. Warmer waters can cause the eggs to be laid earlier and develop faster than eggs that are laid in cooler water. The larvae that hatch from eggs in warm water are also smaller than those that develop in cooler water. Smaller larvae are more vulnerable to changing ocean conditions and predation. Changing the timing of when eggs are laid, and hatch may mismatch the new larvae with the timing of the plankton they eat when they hatch and cause mortalities. Finally, warmer waters contain less dissolved oxygen and so as oceans warm, there is a higher risk of anoxic dead zones forming where animals cannot get enough oxygen. However, given that halibut are a highly mobile species, they are likely to be more resilient than seafloor creatures such as crabs or sedentary ones such as clams and cockles. Nonetheless, warming waters will likely cause additional halibut mortalities that could reduce the availability of an important resource.
OCEAN ACIDIFICATION WILL NEGATIVELY IMPACT THE FOOD HALIBUT RELY ON, REDUCING POPULATION SIZE AND HEALTH.
Young halibut that live exclusively on the ocean floor rely heavily on crustaceans for prey. Crabs face multiple stressors, including ocean acidification damaging their shells and warming waters reducing the area where they can live, and declines in crab populations will result in halibut going hungry.Adult halibut seek out a wider variety of food sources, and although the clams, fish and crabs they rely on are likely to be negatively impacted, the broader range of species adult halibut eat will help make them more resistant to change.
GIVEN THE WIDE RANGE OF HALIBUT HABITAT, THEY ARE LIKELY TO BE MORE RESILIENT THAN OTHER SPECIES OF FISH.
Pacific halibut range from California, through the Bering Sea and across to Japan, meaning they’re already adapted to a wide variety of temperatures. While juveniles face heightened risks from climate change, individuals that survive to adulthood seem relatively well suited to do well even in changing environmental conditions. Thus, despite the threats to halibut listed above, it is likely that community members will be able to catch sufficient halibut in the future, though it may take more effort.
1.1: Monitor Halibut populations and sizes
1.2: Investigate options for adapting fishing techniques, such as fishing in deeper water
1.3: Educate the community about negative impacts on halibut stemming from increasing water temperatures
2.1: Increase participation in government management of Halibut
2.2: Reduce impacts of commercial fishing
3.1: Consider aquaculture as a means of assuring long-term access to Halibut and other marine resources
3.2: Policy protection for small-scale and local resident fishermen and subsistence fishermen to maintain access to diminishing resources while limiting large-scale fishing harvests