EXPERT OPINION : Dr. Kevin Rhodes, Affiliate Faculty, University of Hawaii



Posted on 06 November 2013  | 
Kevin Rhodes, Affiliate Faculty, University of Hawaii
© Kevin RhodesEnlarge

Tell us a little bit about yourself, what you do, and how you got started in this profession.

I am a Ph.D. coral reef fisheries biologist/ecologist with 15 years of experience. I am actively engaged in a number of fisheries management and conservation activities, including basic life history (age, growth, reproduction) assessments of coral reef fishes that include top predators and herbivorous fishes.

My main focus in recent years has been identifying the most appropriate design and size for Marine Protected Areas (MPAs), particularly those situated on and around fish spawning aggregations (FSA).

The target species I have focused on have been three groupers listed as Vulnerable (squaretail coralgrouper, Plectropomus areolatus) or Near Threatened (camouflage grouper, Epinephelus polyphekadion and brown-marbled grouper, Epinephelus fuscoguttatus), which are critically important food fishes for numerous Indo-Pacific island communities and which are prime targets of the Southeast Asia Live Reef Food Fish Trade (LRFFT).

I have focused quite a lot of this work in Pohnpei, Micronesia, however I have also conducted similar projects in Ayau, Indonesia and have ongoing collaborative projects in Mait Island, Papua New Guinea and Solomon Islands.

I also have ongoing acoustic tagging work looking at MPA effectiveness for near shore reef sharks and whether these sharks utilize FSA as opportunistic feeding sites during grouper reproductive periods.

Since I was young, I always wanted to be a biologist. As a kid, I watched The Undersea World of Jacques Cousteau every Sunday, which opened my eyes to the marine world. My first experience in marine science was as an undergraduate doing laboratory studies on marine algae.

Under Dr. Clark Hubbs, one of the preeminent freshwater fish biologist of his time and the son of Dr. Carl Hubbs, who volunteered under David Starr Jordan, I carried out my first fieldwork on fish, which involved researching the effects of a red tide bloom in a West Texas River (the Pecos).

I then moved to California and attended Moss Landing Marine Labs and graduate studies under Dr. Gregor Cailliet, where I conducted an examination of the nearshore fishes of the Yellow Sea, China.

Afterward, I ended up studying for my Ph.D. under Dr. Yvonne Sadovy, another preeminent scientist at the University of Hong Kong, where I moved into studies of tropical reef fish and became aware of the negative impacts of the LRFFT.

My first stop during my Ph.D. fieldwork was Pohnpei, Micronesia, where I identified the largest known grouper FSA in the Pacific at that time. I have continued to work there ever since to conserve that and other FSA since 1997.

You are currently working with WWF on an acoustic tagging project for certain grouper species in Solomon Islands. What is acoustic tagging and how does it work? What do you hope to achieve from this activity?

Acoustic tagging uses transmitters that produce sonic (sound) waves with unique pulse intervals, which are then picked up by moored underwater receivers. Each tag can be used to identify individuals, providing a time and date stamp and individual ID when the fish passes within range of the receiver. Receivers can be placed anywhere on the reef; we choose receiver locations where we
  1. think the fish might be going, or
  2. where MPA boundaries already exist, or
  3. where fishes might be particularly vulnerable to fishing outside an existing MPA, such as along migratory routes.
We implant these tags internally using sterile surgical techniques following the capture of the fish. Once implanted and following fish recovery, the fish are released to resume normal activities. We tend to target fish on spawning aggregation sites to examine fish movement within and around spawning sites (spatial dynamics) and look at sex-specific differences during reproductive times (temporal dynamics).

I have focused a lot of this research at the Kehpara Marine Sanctuary in Pohnpei to determine spatial and temporal trends. From the work in Solomons with WWF, I hope to accomplish the following:
  1. identify sex-specific patterns of movement at and away for FSA for effective MPA design;
  2. verify spawning seasonality;
  3. look at sex-specific residency times at the FSA that may impart increased fisheries vulnerability to individual sexes as well as populations (i.e., if sexual selection of, for example, males occurs, rendering populations unable to maximize fertilization);
  4. determine catchment areas (i.e., where these fish are coming from to spawn at this site).

How can data from acoustic tagging aid efforts in Ecosystem-Based Fisheries Management (EBFM), the protection of critical grouper habitats, and sustainable reef fisheries?

Spawning habitats are critical habitats and FSA for groupers typically are also important spawning sites for other species of fish. By delineating areas used by these fish to reproduce and by properly designing and placing MPAs around these areas, the research provides expanded protection for a number of species.

Moreover, protecting groupers through properly designed MPAs that are effectively enforced maximizes potential reproductive output, enhancing potential larval recruitment and eventually fisheries. For local people, this ensures future fisheries livelihoods and food security and sustainability for the future.

What kind of grouper species are you targeting for this acoustic tagging activity? How significant are these species to Solomon Island’s domestic consumption, local livelihood, and overall socio-economic standing?

We don’t really know where these species lie in terms of importance, but they are important food fishes and are common at markets, particularly during reproductive periods. They formed a bulk of the LRFFT in past years, where they were targeted at FSA sites. In some instances, these FSA were virtually extirpated.

While we don’t have a handle on how much income is coming from these fisheries, we may assume it is not negligible and without these species, income would be impacted. These species are also top predators and play an important role in ecosystem maintenance and function.

What are the current threats and challenges facing these grouper species in the Pacific and what are their imminent impacts on the environment, livelihoods, and food security?

Again, these species remain a primary component of the LRFFT regionally. Past studies have shown that the trade appropriates 30-60% of the sustainable grouper production within the Indo-Pacific. This trade is ongoing.

The loss of these fishes has important ramifications for reef function, resilience and maintenance. The loss of any component of the fishery will have socio-economic and food security repercussions, particularly given that Solomons is forecast to move beyond sustainable consumption of food fishes by 2030.

A failure to address the ecological and management needs of these species will certainly impact future food security and the ability of these fish populations to persist in the region.

There are discussions around how mariculture, if done responsibly, can be a solution to food and livelihood security issues in the Coral Triangle region. Do you think that grouper mariculture in the Pacific is the way to go? What are the pitfalls that should be avoided and how can we best address these in this part of the world?

My opinion is that aquaculture is sometimes put forward as a panacea and replacement for proper fisheries management and conservation, at least for carnivorous top predator fish. Aquaculture in theory may offset overall consumption, but as with the salmon scenario, in reality it often does not reduce demand or the wild capture of these species.

Top predators are poor choices for aquaculture as they require tremendous amounts of food, usually lower tropic level species or industrially farmed products to be cultured to a viable size for sale. There are already problems with aquaculture in terms of wild capture of juveniles, genetic contamination of wild stocks, disease and hybridization within aquaculture facilities.

Kevin Rhodes, Affiliate Faculty, University of Hawaii
© Kevin Rhodes Enlarge
Tag insertion procedure
© Richard Nemeth Enlarge
Tag insertion in a squaretail coral grouper.
© Richard Nemeth Enlarge
Acoustically and conventionally tagged highfin coral grouper.
© Richard Nemeth Enlarge
Release of a brown-marbled grouper by a local college intern.
© Richard Nemeth Enlarge

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