A new NOAA Fisheries study now underway is looking into the relationship between fish condition and reproductive success in varied habitats, with a focus on deep-sea coral and sponge ecosystems.
Part of this research includes developing methods to accurately assess the condition of rockfish by measuring their fat content, since for Alaska rockfish fat signifies health.
Evidence compiled by researchers suggests that fish with higher energy reserves (of fat) are more reproductively successful and therefor more productive.
Several species of rockfish in Alaska have been shown to skip spawning in certain years. Scientists are uncertain if this reproductive failure is related to body condition.
The focus of the study is the most commercially important rockfish in the Gulf of Alaska and Aleutian Islands: Northern rockfish and Pacific ocean perch. Samples are being collected during the Alaska Fisheries Science Center’s 2021-2022 bottom trawl surveys.
Study leader Christina Conrath, a biologist at the Alaska Fisheries Science Center, said that developing a feasible way to accurately measure fish condition in Alaska waters during annual surveys will provide much data to help scientists understand how habitat influences fish productivity. Such knowledge will also help her team track how climate change is affecting the ecosystem, she said.
The project is part of NOAA’s Alaska Deep-Sea Coral and Sponge Initiative, which is supported by the Deep Sea Coral Research and Technology Program. That initiative was established to provide data needed to inform management and protection of deep-sea coral and sponge ecosystems in Alaska.
Alaska’s rockfish are frequently found in coral and sponge habitat. Previous research by the Alaska Fisheries Science Center determined that rockfish densities were highest in structurally complex habitat, but that research showed no evidence that structure created by corals and sponges was more important than that formed by rocks.
While researchers know rockfish get value from structure, they do not yet have evidence that coral and sponge habitat offers benefits beyond structure, Conrath said.
At the science center’s Auke Bay laboratories, biologists validate results from two tools to improve their understanding of how important deep-sea coral and sponge habitat. The Yamato Fish Analyzer measures impedance (resistance to electric current), and the Distell Fatmeter measures water content.
“If we can monitor fish condition, we can see what is happening with different species,” Conrath explained. By seeing which conditions help fish do well or do poorly, she added, “we can adapt and prepare for future change.”