IPHC to investigate ‘chalky’ halibut among research plans

After years of hearing concerns from fishermen about the prevalence of “chalky” Pacific halibut, the International Pacific Halibut Commission is planning to gather information for an investigation into it.

Chalky halibut are fish that, when cut open, have a stiff, chalk-textured flesh as opposed to the normal pale and tender flesh. Chalky meat is not dangerous to humans but is not desirable and thus costs the fishermen at the dock.

Dr. Josep Planas, who heads up biological research for the IPHC, noted plans to gather information about chalky halibut from stakeholders this year before moving forward with designing a study on it.

“What we plan is to initiate this project by collecting information from stakeholders on the incidence of chalky flesh and trying to understand the conditions that lead to its development,” he said. “We would love to get any information from any stakeholders on this topic.”

Chalky halibut is not a new phenomenon; fishermen and researchers have been seeing it for decades.

IPHC research from the 1960s and 1990s connect the prevalence of chalky flesh with the buildup of lactic acid in the fish and lowered pH in the fish after death.

Researchers have associated it with warmer ocean temperatures near the bottom, according to the IPHC. When the bottom temperatures reach 12 to 14 degrees Celsius, they tap at the upper thermal limits of Pacific halibut distribution, according to the IPHC.

“The condition is reversible in live fish,” according to the IPHC’s website. “Flesh which might otherwise turn chalky does not develop the condition post-mortem if the fish are allowed a 1-2 day resting period after capture, and before killing.”

The project is one of a host of research projects the IPHC is planning for the next two years. Those projects focus on topics including migration, growth patterns, reproduction, genetics and discard mortality, Planas said.

He said the migration study, which incorporates a number of different methods for tracking fish through their migration patterns, will likely produce some results on larva distribution in 2019. The study on reproduction, which aims to craft a more detailed picture of the full Pacific halibut lifecycle, will likely produce results in early 2020.

Researchers are also taking advantage of a new tool on many commercial fishing vessels: electronic monitoring. Some fishing vessels, to save the aggravation and expense of having a human observer on their boats, are opting to install cameras and other electronic systems to monitor their harvests and bycatch.

After the first year, the National Marine Fisheries Service reported implementation and compliance went smoothly, with plans to enroll 165 vessels for 2019.

The researchers are taking advantage of the presence of electronic monitoring devices onboard to test out different methods of tagging and tracking fish, Planas said.

The IPHC is working on a study on discard-related mortality, and specifically how handling and release methods affect halibut injury and outcomes. On vessels with electronic monitoring, the researchers were able to closely track release methods and verified that the data was good.

“What we can say so far is when you compare the electronic monitoring-determined release method to the actual, the correlation is incredibly high,” he said. “Sometimes 100 percent, but close to 97 to 95 percent. EM captures very well the release method.”

The researchers are working on results to determine how release methods impact the fish’s condition upon release and thus survival. Planas said the study includes both the commercial and recreational sector and results may be incorporated into stock assessments as soon as late 2019 and 2020.

The purpose of the research program is to fill in gaps about knowledge of Pacific halibut stocks and life history, he said. In the future, the IPHC is planning to work with other researchers for studies on whale detection techniques and possibly using LEDs on trawls to trigger flight responses in Pacific halibut, thus helping to reduce trawl bycatch, Planas said.


Elizabeth Earl can be reached at [email protected].

02/13/2019 - 10:04am