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    Wednesday, June 19, 2019-11:03:13A.M.

     

     

     

     

     

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Age matters even for fish

WE should care about the age of the fish we eat, according to Allen Hia Andrews, Ph.D., a research fisheries biologist with the National Oceanic and Atmospheric Administration’s Pacific Islands Fisheries Science Center.

In a presentation on Thursday at Joeten-Kiyu Public Library, he discussed the life history of fish and why it’s important to know how old they are.

The audience included Eric Cruz and Mike Trianni of the Pacific Islands Fisheries Science Center; John Gourley of Micronesian Environmental Services which manages the CNMI Bio-Sampling Program for NOAA’s National Marine Fisheries Services; a representative from the Division of Fish and Wildlife, a few people involved in local fishery; and a handful of students.

Allen Hia Andrews, Ph.D., a research fisheries biologist with the National Oceanic and Atmospheric Administration’s Pacific Islands Fisheries Science Center, speaks on the life history of fish at the Joeten-Kiyu Public Library on Thursday last week.  Photo by Emmanuel T. EredianoAllen Hia Andrews, Ph.D., a research fisheries biologist with the National Oceanic and Atmospheric Administration’s Pacific Islands Fisheries Science Center, speaks on the life history of fish at the Joeten-Kiyu Public Library on Thursday last week. Photo by Emmanuel T. Erediano

Andrews, who specializes in how long fish and other marine organisms live, said that in many cases, there are estimates of fish age but they lack validation.

But the nuclear bomb tests in the 1950s and 1960s created a very time-specific global radiocarbon signal, he added. This provided a means to determine how long fish can live by analyzing the radiocarbon in the fish’s ear bones known as otoliths, he said.

These otoliths have growth zones that can be counted. A yelloweye rockfish caught in Alaska, for example, was estimated to be over 100 years old based on the growth zone count in the cross section of its otolith.

With the use of a “very expensive instrument,” the radiocarbon signal created by the nuclear bomb tests is extracted from the ototliths and then measured, Andrews said.

This method, he added, involves an innovative comparison of “radiocarbon values recorded in otolith carbonate relative to regional radiocarbon records from hermatypic corals.”

Andrews said the “temporal specificity of the measured levels provide an independent determination of age for corroboration of age estimates from growth-zone counting in otoliths.”

Understanding the full life-history of fish is important in fisheries management, he said. Knowing the age of fish helps people develop proper models to create long-term sustainability for the fishery, he added.

People, in other words, should know when the fish mature and how many years it takes for each fish species to become reproductive.

“Sustainability is the key word. Understanding the life history helps develop proper models to create long-term sustainability, so the fishermen don’t have to worry about whether they are taking too many or have not taken enough.”

Asked if the lifespan of fish is getting short, Andrews said no.

“The lifespan is not changing. I think it is just that we did not know how long they could live. So we are now just discovering in many cases, how long they can actually live.”

In a separate interview, John Gourley of Micronesian Environmental Services said in managing fisheries, there are various life-history metrics that should be known in order to sustainably manage fish stocks under the Magnuson-Stevens Act.

Managers want to know the size and age of fish being harvested, the size and age when a particular species reaches sexual maturity, and the maximum size and age of the species, he added.

In-water surveys also need to be conducted to obtain estimates of species abundance in the ocean, and to better understand the amount of fishing effort — both commercial and recreational, Gourley said.

There are many other factors that should be considered.

“So basically you use all this information to assist in determining whether or not a particular fishery is taking too many fish out of the ocean,” Gourley said.

There was a recent stock assessment for CNMI bottom-fish, and the results indicate that stocks are in very good shape and are considered under-fished, he added.

“That means we could double or triple our existing bottom-fish landings and it still would not exceed the threshold of being in a state of overfishing.”

But as for reef fish, he said, “it is a different story as we don’t have basic life-history information for the many species that compose our catches.”

And this was the reason why Andrews and Eric Cruz of the Pacific Islands Fisheries Science Center were on Saipan. They conducted a workshop for the local Division of Fish and Wildlife and CNMI Bio-Sampling Program staff on how to prepare and read otoliths.

“We have to be careful with our reef fish because they are so accessible and are the favorite food of local residents,” Gourley said.

In cooperation with Saipan fish vendors, he added, the Pacific Islands Fishery Science Center, DFW and the Bio-Sampling Program are collecting life-history information so that local and federal fishery managers will be able to manage the CNMI’s reef fish stocks sustainably.