Less fishing, more fish
Researchers examine fish stocks recovery
Fish stocks could increase by 250 percent on Maui and 350 percent on Molokai if fishing were not allowed in certain areas of the islands, according to a recently released study.
The study led by researchers at the University of Hawaii at Manoa identified areas in Hawaii that would provide the greatest increase in coastal fishery stocks, if effectively managed. Fish stocks were predicted to increase by more than 500 percent on average for some areas on Oahu — the island with the most fishing.
Kostantinos Stamoulis, co-lead author and doctoral candidate, said Thursday that locations with the highest potential on Maui were Maalaea Bay and West Maui shores, particularly between Kaanapali and Olowalu. For Molokai, the ideal sites were south and northwest shorelines.
“These numbers are for full recovery of stocks if fishing pressure was completely removed,” Stamoulis said.
Projected full recovery time of Maui County’s various reef fish would vary depending on the lifespan of the fish, Stamoulis said. Goatfish and small parrotfish are estimated to take 10 years, while jacks, surgeonfish and large parrotfish may take 20 to 40 years to fully recover.
“With longer lifespans, it takes longer for the population to reach reproductive status so it can start reproducing,” he said.
The study relies on data from another report published in April on commercial fishing and recreational, or subsistence, fishing. The report is the first to analyze the two fishing categories in an island-by-island scale.
Ivor Williams, a reef fish researcher at the National Oceanic and Atmospheric Administration and co-author of both studies, said the April study provides researchers with data at the recreational level, which has previously never been collected “at a scale that’s useful.”
The data does not make a judgment on whether there is too much fishing or not, but rather gives other studies context and understanding for their own findings, he said.
Researchers found that about 10 percent of Maui households fished in the previous two months, which comes out to about 270,000 trips per year, or 750 a day. The total weight of fish caught per year for recreational or subsistence fishing is six times larger on Maui than what is caught by commercial fishers.
Williams said the disparity provides context of the yearly catch rate between commercial and noncommercial fishing. He said management has traditionally been focused on commercial fishers who are licensed and required to report their catches.
“Often management agencies will consider that group the most important to regulate when in reality the total amount of fishing in the noncommercial sector is greater,” he said. “Really and truly, that should get more resource management.”
Molokai’s noncommercial haul of fish is 18 times larger than the commercial take per year, the largest disparity in the state. Lanai’s is seven times as large. About 25 percent of Molokai households had someone fish in the last two months with Lanai reporting 19.5 percent.
Stamoulis said the report by lead author and UH researcher Kaylyn McCoy helped him develop detailed maps for fishing pressure across the state. His report identified fish stocks with the greatest potential by analyzing how close roads were to the shoreline, shoreline steepness and accessibility, and how close it was to residents.
“The assumption was that the more accessible areas were fished more,” Stamoulis said of his study with co-lead author and geospatial analyst Jade Delevaux.
The rural areas of every island were generally the least fished and could support abundant stocks of reef fish with high quality habitat. Stamoulis characterized the north shore of Molokai and the east and southeast shores of Maui to be in “good shape.”
“Those parts of Maui and Molokai are really hard to access and don’t get a lot of waves and are blasted by trade winds, which really protects it from fishing,” he said.
Healthy fish stocks are important because they serve as marine reserves for surrounding reefs, Stamoulis said. Large fish produce disproportionally more eggs and larvae, which drift on ocean currents to nearby and faraway areas. Adult and juvenile fish also can “spill over” to nearby areas.
“If you protect currently healthy areas, they’re already providing service and ensure a supply to other fisheries in the future,” he said.
The state Department of Land and Natural Resources is prioritizing management throughout the islands, which could include no-take areas or limits on types of fish. The state has committed to managing 30 percent of Hawaii’s nearshore waters by 2030.
“This new study will help us identify those areas with the greatest potential for increasing reef fish populations on all islands,” said Bruce Anderson, administrator for the DLNR’s Division of Aquatic Resources. “This scientific information will be compared with an ongoing spatial analysis as part of the Marine 30×30 Initiative. Ultimately our intention is to combine this information with local knowledge and collaboratively identify what to do in management focus areas.”
The two reports follow a 17-year study released late last year that determined overfishing to be the primary cause of reef fish declines in Hawaii — Maui and Oahu being the most impacted.
According to that study, the abundance of food fish species — those primarily caught for human consumption — is lower in populated areas, while there is no difference in the abundance of nonfood fish species — those not generally targeted by fishing — between populated and unpopulated areas. Scientists suggested that fishing, rather than other human influences such as pollution or habitat degradation, is primarily responsible for the differences.
* Chris Sugidono can be reached at firstname.lastname@example.org.