Hawaii Goby Fish That Can Climb Up Waterfalls Under Threat as Unmaintained Waterways Benefit Invasive Species

Unmaintained waterways provide an ideal habitat for invasive species, while they also pose a threat to the Hawaii goby fish, a species that can scale waterfalls with their suction mouths.

Hawaii Goby Fish

University of Hawaiʻi at Mānoa research delves into ʻoʻopu nākea, a unique Hawaiian goby fish.

These fish exhibit a mountain-to-ocean lifecycle, starting in the sea and returning to freshwater streams to mature. Their fused pelvic fins act as suction cups for scaling waterfalls during migration.

Sadly, climate change and human interference jeopardize these native species.

Prior studies suggested they no longer relied on the ocean. But using advanced microchemistry, the UH Mānoa team found that 100% of ʻoʻopu nākea still crucially depend on the ocean during larval development.

This underscores the vital need to safeguard Hawaiʻi's freshwater ecosystems.

Impact of Unmaintained Waterways

Yinphan Tsang, a study co-author and head of UH Mānoa's Tsang Stream Lab, warned that neglecting waterways will reduce native species.

Larvae can't reach the ocean, and juveniles can't return upstream. Neglected waterways may see an influx of invasive fish, competing with natives.

The study, involving UH Mānoa, Oregon State University, US Fish and Wildlife Service, and UK Center for Ecology and Hydrology, emphasized the interdependence of freshwater and ocean ecosystems in Hawaiʻi.

Shaya Honarvar, UH Pacific Cooperative Studies Unit director, stresses the importance of integrated ecosystem management, deeply rooted in Hawaiʻi's history.

The research underscored the need to monitor and protect water bodies, aiding native species migration and population growth.

Migratory Patterns

Researchers gained insights into the life cycle of ʻoʻopu nākea, a native Hawaiian amphidromous species.

Larvae are born in freshwater, flow to the ocean, and juveniles migrate upstream to complete their life cycle.

Decreased rainfall and more frequent droughts have reduced water levels in Hawaiʻi's streams, disconnecting some from the ocean and altering their flow patterns. Streams diverted for agricultural use further limit downstream flow.

Gordon Smith, a US Fish and Wildlife biologist, emphasizes the impact of human modifications on streams and estuaries, which are vital for conserving ʻo'opu nākea and other migratory freshwater organisms in Hawaiʻi.

Otoliths From 90 Fishes

The Hawaiʻi Commission on Water Resource Management plays a crucial role in monitoring and regulating stream diversions across the state, ensuring sufficient water resources for both the community and native flora and fauna in specific habitats.

Researchers utilized a new microchemistry method to investigate the migratory history of ʻoʻopu nākea by studying otoliths, tiny calcium carbonate structures in fish heads used for balance.

Unlike previous approaches involving polishing, which risked removing critical microscopic portions, their team opted for non-polished analysis.

This approach aligns with their mentor's wisdom, the late Dr. Bob Kinzie III, who believed in the truth of otoliths, urging us to listen closely to their stories.

Otoliths, akin to tree rings, accumulate daily, with the center indicating the larval phase and outer rings representing adulthood.

By employing elemental microchemistry at Oregon State University's W.M. Keck Collaboratory for Plasma Spectrometry, researchers delved into the larval environment of 90 fishes, concluding that all spent their larval stage in saltwater.

Jessica Miller, an Oregon State University professor, commended Cody's work as pivotal for future research and conservation of endemic Hawaiian gobies like 'o'opu.

Hannah Clilverd, an ecosystem scientist at the UK Centre for Ecology and Hydrology, noted that this research enhances our understanding of 'o'opu migratory patterns and their streamflow needs, aiding in their survival.