Reef Fish Movement Patterns in Hawaii Marine Protected Areas

Long-term Movements of Reef Fishes at Kealakekua Bay MPA

Principal Investigator: Carl Meyer

Project Overview

Kealakekua Bay MPA

Figure 1. Kealakekua Bay Marine Life Conservation District, Hawaii

Overfishing is widely believed to have drastically reduced reef fish populations in the Main Hawaiian Islands. Marine Protected Areas (MPAs - areas where fishing is prohibited) can help to reverse overfishing by allowing fish to grow to maturity in a protected environment, and produce larvae to replenish surrounding areas. However, to prevent fish simply roaming into fished areas and being captured, MPAs must be large enough and contain appropriate habitats to keep resident fish inside protected area boundaries. Despite this very basic MPA design requirement, we actually know very little about the scale and patterns of movements of most coral reef fishes. We are tracking the movements of reef fishes captured inside Kealakekua Bay Marine Life Conservation District (Hawaii) by implanting them with small transmitters and deploying small underwater listening devices inside Kealakekua Bay and along 100 km of the adjacent west Hawaii coastline.

Research Questions

We asked three specific questions about reef fish long-term movements at Kealakekua Bay:

Are reef fishes permanent residents of Kealakekua Bay?
Do their daily movements take them back & forth across the MPA boundary?
Does a wide sandy channel inside Kealakekua Bay function as a natural barrier to reef fish movements?

Fish movement data obtained in this study will be used to produce simple guidelines for designing more effective MPAs.

Methods

We captured 70 coral reef fishes inside the core no-fishing area of Kealakekua Bay Marine Life Conservation District and surgically implanted them with small acoustic transmitters. We selected heavily targeted species from among from 3 major feeding guilds (herbivore, planktivore and benthic carnivore). Fish were kept in a holding cage overnight and released close to their capture locations the following morning after checking to ensure that they were in good condition. All fishes swam away vigorously on release.

We deployed 8 underwater receivers at Kealakekua Bay to monitor fish movements across MPA boundaries and across habitat breaks within the MPA. These receivers identify and record the presence of any acoustic transmitters within range (up to 250 m). The receivers have a battery life of approximately 15 months and are being downloaded at 3- month intervals. The receivers at Kealakekua Bay are part of the West Hawaii listening array consisting of 37 receivers deployed along 109km of coastline.

Divers prepare to catch fish

Figure 2. SCUBA divers prepare for nighttime fish capture.

Parrotfish captured for tag implant

Figure 3. A captured redlip parrotfish is prepared for transmitter implantation..

Results

Individuals from among a wide variety of reef fish species were highly site attached and showed long term fidelity to Kealakekua Bay MLCD. Most fish exhibited diel habitat shifts and moved predictably between separate day and night habitats within their home ranges. The scale of reef fish movements varied among species with blue goatfishes and sleek unicornfishes exhibiting wider ranging movements (>1 km) than most surgeonfishes and parrotfishes. Wider-ranging species moved back and forth across the MPA boundary between protected and fished areas. Tagged fishes moved back and forth along a contiguous reef shelf but with one exception (sleek unicornfish) did not cross the wide sandy channel inside Kealakua Bay.

Reef Fish Space Use Bubble Plot

Figure 4. Bubble plots of spatial distribution of detections of each species. Shaded area = land.

Ongoing Coral Reef Fish & Marine Protected Area Research

Results from Kealakekua Bay indicate most reef fishes will move readily within contiguous reef habitat but may be reluctant to cross major habitat breaks (i.e. habitat breaks may be barriers to reef fish movements). We now have funding from Sea Grant to quantify the movements of coral reef fishes within a highly-fragmented habitat (patch reefs in Kaneohe Bay, Oahu). These patch reefs are 'islands' of coral reef habitat separated by open expanses of soft sediment. The overarching goal of the project is to gauge the role of herbivorous reef fishes in controlling invasive algae, and the specific aim of the fish tracking component is to determine whether herbivores are restricted to a single patch reef or whether they routinely move among different patch reefs, crossing open habitats in the process. The Coconut Island Marine Life Conservation District patch reef will be used as the MPA habitat in the study.

Project Publications

Meyer CG, Papastamatiou YP, Clark TB (2010) Differential movement patterns and site fidelity among trophic groups of reef fishes in a Hawaiian Marine Protected Area. Marine Biology. 157:1499-1793. DOI: 10.1007/s00227-010-1424-6

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