Chamorro Standard Time: Tuesday, September 26, 2023 - 04:48 AM





Aquatic Section


Picture shown: Chellinus undulatus, (Humphead wrasse: Napoleonfish);Chamorro name: Tangison.

You may also use our fact sheets found under the page, “Educational Outreach” as “Species Fact Sheets” to view more fish on Guam.

Fishing activities on Guam can be divided into offshore and inshore fishing. Offshore fishing typically involves small boat (12 to 48 feet), 1 to 2-day trolling and bottom fishing trips that usually originate from one of the three principal harbors located on the west coast and southern tip of the island. In recent years, the sportfishing charter boat industry has increased significantly. Inshore fishing is typically conducted without the use of a boat and consists mostly of nearshore casting, netting, and spearfishing. In addition to artisnal/non-commercial fishing, there is a commercial fishery on Guam, with fish sold through a cooperative and several other vendors. Roadside vendors often sell their individual catch or fish imported from other islands.

The Aquatic Section of DAWR has been conducting offshore and inshore surveys since the early 1970’s. The data are the basis for management proposals such as the Marine Preserve Areas. This section of the web site includes the annual reports since 1990-2000, which detail data and conclusions.

The Aquatic Section helps to develop the fisheries by placing fish aggregation devices (FADs), fishing platforms, and other aids to fishermen, while at the same time monitoring and managing the fisheries through initiatives to foster health of the reefs on which the fish depend, including placing shallow water moorings to prevent reef damage and setting aside Marine Preserve Areas (restricted or no fishing) to help restock the fishing areas.

The Aquatic Section also takes care of the freshwater fisheries and habitats, including monitoring for introduced pest species of animals and plants. They take a watershed approach to fisheries management, recognizing that what happens on the land can flow down via the rivers to to reefs (poster in development for 2013).

Important parts of work of the Aquatic Section are education and conservation. Explore their projects in the EDUCATIONAL OUTREACH tab of this webpage; these will include posters and pamphlets (thumbprints to be added at a later date).

FADs and SWMs


Fish Aggregation Devices, or FADs, and Shallow Water Moorings (SWMs) have been placed around Guam as aids to fishermen. FADs enhance access to Guam’s popular coastal pelagic fishing grounds. SWMs maintained at popular fishing and recreational diving locations minimize anchor damage to reef habitats.

Fish Aggregation Devices

Fish aggregating device (FAD) activity focused primarily on the reestablishment of FAD systems at existing locations (photos below; see report for map and design). The project also involved enhancement projects such as the production of FAD location maps for fishers and the improvement of the current FAD system design to extend the average time on station. FY12 activity under F-3-D consisted primarily of reestablishing FADs from existing sites. During FY12, 15 missing FADs were replaced on the west side of the island.

Details, including map of locations and diagrams of devices. Click here to download a copy:  FAD_093014

Shallow Water Moorings

Moorings are intended to accommodate a mixture of user groups and a wide variety of vessel lengths, ranging from subsistence fishing in a small skiff, to scuba diving from the larger 40-foot tour-boats carrying 30-50 recreational divers. However, the majority of vessels utilizing the SWMs are expected to be in the 14 to 25-foot range. To ensure their availability and to prevent the mooring systems from being overloaded, decals have been affixed to the SWM buoys that indicate a 3-hour time limit, a maximum boat length of 50 feet, and a maximum weight of 35 gross tons.

To view the map for SWMs, click here: Map-SWMsmapcopy

*An updated map showing offline/online SWMs and FADs is being developed as of July 8, 2013.

Commercial Fishing


Commercial landings amounted to 494,000 lbs (=224,000 kg or 224 m.t.)* with a value of $1.09 M US dollars. (Details found in the commercial fisheries annual report). Trolling of 5 pelagic species (skipjack tuna, yellowfin tuna, mahimahi, marlin, and wahoo) were accounted (see offshore fisheries). The reef fishery involves mixed species as well as particular fisheries such as atulai and mañåhak (see inshore fisheries). 

The commercial fisheries program was established in 1979 to gather data related to the caught and sold fishery resources on Guam. The program was initiated by the National Marine Fisheries Service (NMFS) Honolulu Lab and at first data were collected only from the Guam Fishermen’s Cooperative Association in Hagatña. The program has slowly changed over time and many of the early participants have gone out of business. Participation in the program is voluntary, and does not reflect the entire commercial fish sales on Guam. DAWR continues to encourage other vendors to participate.

As part of the long-term program plan, data collection and management has shifted from NMFS in Hawaii to the Aquatic Section of DAWR. Program responsibility has slowly increased to the point where DAWR now handles data collection, computer input, and production of commercial landing tables. The Aquatic Section monitors, analyzes and reports locally caught fish sales and related activities through the collection of NMFS-issued vendor’s receipt books. All data collections are forwarded to NMFS Honolulu Lab for their regional report requirements.

Please visit NMFS website for current data: Or visit their website:

Coral Reef Initiative

Guam is part of the International Coral Reef Initiative.

The International Coral Reef Initiative (ICRI) is a partnership among nations and organizations seeking to implement Chapter 17 of Agenda 21, and other international Conventions and agreements for the benefit of coral reefs and related ecosystems. The Initiative was established in order to stop and reverse the global degradation of coral reefs and related ecosystems. The ICRI partnership and approach thus far has been to mobilize governments and a wide range of other stakeholders in an effort to improve management practices, increase capacity and political support, and share information on the health of these ecosystems. The first International Coral Reef Initiative Workshop was held in the Philippines in June 1995. Its aim was to enable countries, donors, and development and funding agencies to work with coral reef managers, private sector representatives, non-governmental organizations and scientists to develop a Call to Action and a Framework for Action for achieving sustainable management of coral reefs and related ecosystems. The Call to Action highlighted the significance of coral reef ecosystems to sustainable development. ‘Coral reef ecosystems offer benefits to humankind beyond those realized for food production, tourism, recreation, aesthetics, and shoreline protection. Capable of sustaining innumerable coastal communities worldwide, these ecosystems also have great economic, social, and cultural importance to nations, and to entire regions. As competition among multiple uses of reef resources increases, so too will their significance to the human populations that depend on them.’ Continuing degradation of coral reefs and related ecosystems and their resources may increase the conflict amongst users and threaten environmental and food security. Coral reefs are the life support system for the existence of small island developing states and many coastal communities of developing tropical countries.

The purpose of the Call to Action was, and remains, to mobilize governments and the wide range of other stakeholders whose coordinated vigorous and effective actions are required to address the threats to reefs. The Framework for Action calls for action in four major areas:

• Integrated management;• Capacity building;• Research and monitoring; and• Review.

The Dumaguete City workshop (Philippines, May-June 1995) set in place a strategy for subsequent action under ICRI, including endorsement of the need for periodic review of the extent and success of ICRI implementation as an essential element of the ICRI strategy.

Major data base on reef info: Reef Base: reef resources of Guam

Inshore and Offshore Fisheries

Text under revision 2015.


Effective management of Guam’s inshore fishery resources requires accumulating data on the types of fishing methods used, fishing pressure, and annual catch. To identify trends in fishing participation, effort, and catch, the Division of Aquatics and Wildlife Resources (DAWR) has been monitoring day and night coastal fishing activities since FY85. Over this period of time, survey and analysis methodologies have changed in response to fluctuations in budget and staff. In the last several years, however, field survey techniques have been expanded and refined, while estimates of Guam’s recreational and subsistence fishing activities have come to be based on more reliable data analysis techniques.

OffshoreDocument Actions

Effective management of the island’s offshore fishery resources requires the collection and analysis of boat-based offshore data on participation, fishing effort, methods used, and harvest. The Fisheries section at the Department of Agriculture’s Division of Aquatic and Wildlife Resources (DAWR) has been monitoring offshore fishing activities for the past 23 years in order to identify trends in fishing activities. During this period, survey and analysis methodologies have changed in response to fluctuations in budget and staff, changes in the fishery, and the development of computer hardware and software. The National Marine Fisheries Service (NMFS) and DAWR have recently developed a computerized database program to collect and analyze the entire offshore fisheries data collected since FY97.


The FY00 island-wide offshore catch was from primarily small recreational-type vessels and estimated at 98.3 metric tons (m.t.) [Table 1]. For comparison, total commercial landings (including reef fish) for FY00 were 224 m.t. The majority of offshore harvests (64.6 m.t.) were landed by trolling, which consisted primarily of 5 pelagic species [Table 2]. Bottomfishing harvested an estimated 13.4 m.t., snorkel and SCUBA spearfishing harvested a total of 15.5 m.t., while Atulai night-light jigging harvested an estimated 0.3 m.t. Other methods encountered during offshore surveys such as surround net, gill net, cast net, jigging, spin-casting, and other rarely encountered methods, accounted for 4.5 m.t.

[Table 1] Composition of the Guam offshore catch during FY00. Weights are in metric tons (m.t.; 1 m.t. = 1000 kg). [Convert any units online!]Offshore Fishing Method FY00 Catch (m.t.)Trolling 64.6Bottomfishing 13.4Spearfishing 15.5Atulai night-light jigging 0.3Other Methods 4.5Total FY00 Offshore Catch 98.3Skipjack accounts for 45% of the trolling catch.[Table 2] Composition of the Guam offshore troll catch during FY00 by most common species.Weights are in kilograms (kg).Troll Species Total Catch % Troll SpeciesKatsuwonus pelamis 28,903 45Coryphaena hippurus 9,268 14Thunnus albacares 8,865 13Makaira mazara 7,395 11Acanthocybium solandri 6,856 10Elagatis bipinnulata 965 <2Euthynnus affinis 858 <2Sphyraena barracuda 602 <1Gymnosarda unicolor 465 <1Other species 400 <1Total 64,577 100Declining fisheries

An estimated 13.4 m.t. of bottomfish were landed during FY00, a decrease of 79% from FY99 and was dominated by five major families with six species. Significant decreases of all groups of bottomfish were observed in comparison with FY99, which had snappers, emperors, triggerfish, and trevally’s decreasing 70%, 79%, 56%, and 83% respectively for FY00.

Significant decreases were observed for all major bottomfish species caught in FY00, which included: Onaga by 79% (1.4 m.t. vs. 6.7 m.t.); Kalikali by 58% (0.8 m.t. vs. 1.9 m.t.); Lehi by 49% (0.6 m.t. vs. 1.2 m.t.); Red-Gilled emperors by 71% (1.5 m.t. vs. 5.1 m.t.); Yellowstripe emperors by 76% (0.4 m.t. vs. 1.6 m.t.); Blackspot emperors (Lethrinus harak) by 85% (0.3 m.t. vs. 2.1 m.t.); Yellowlip emperors by 88% (0.2 m.t. vs. 1.8 m.t.); and Black-tipped groupers (Epinephelus fasciatus) by 90%.

A decline in participation, effort, and catch, may be indicating a downward trend of the fishery. Fishermen encountered during FY00 expressed concerns that fishing pressure (local and foreign) has resulted in reduced catches and average size, and greater effort to harvest. While weather patterns, such as El Nino events, may additionally affect seasonal abundances of migratory fish stocks, the absence of larger reef fish is not due to the effect of weather and pollution, especially if juveniles are present. We hope that the establishment of the marine preserves on Guam will relieve some fishing pressure and provide sanctuary for larger fishes, which have higher fecundity. Analysis of the size frequencies and catch rates is critical in order to provide an accurate picture of the effect of fishing pressure on food fishes of Guam. Anecdotal evidence from fishermen and data from the offshore creel surveys show that management of the fishing resource is, at the present, crucial in order to halt further depletion of Guam’s fishing resource, especially those fish which are considered valuable, both culturally and economically.

It has become more apparent each year that Guam’s boat-based fishery has significantly impacted the fish resources on Guam, especially by bottom and spearfishing. A historic decrease in catch per unit effort (CPUE) has been observed, indicating a decrease in the populations of reef-associated fish. As boat-based fishing participation continues to rise, so too will the disappearance of adult reef fish with the highest reproductive potential around Guam.

Commercial SCUBA spearfishing presents a serious threat to all reef fish stocks, since a significant portion of the activity utilizes state-of-the-art dive equipment, which allows fishers to perform multi-tank dives up to 3 times a week to ~ 50 m depth. In recent years, managers have been faced with the situation of “bang sticking” larger reef fish species. Bang sticks are designed to be used for shark defense, but some divers also use them to target the more vulnerable and larger reef fishes with high market value. Continued unregulated use of this method will pose a serious threat to the fishery and eventually cause the absence of these ecologically and aesthetically important reef fish species from Guam.

More information: detailed report (FY 2000) and (FY01) update .International fishing

In addition to the offshore fishing carried out from Guam, Guam is also used as a transhipment port for fresh tuna shipment to Japan (caught by longliners), and the Port is also used by purse seiners that catch tuna for freezing at sea on factory ships. These fish are caught in international waters and the fisheries are not monitored by DAWR. For information on these fisheries, visit the Western Pacific Fisheries Information Network.

Guam's Marine Resources

Various information pertaining to marine resources on Guam will be found here.

Guam's Freshwater Resources

Masso Reservoir

The opportunities for freshwater fishing on Guam are limited. With the numerous fishing derbies sponsored by Division of Aquatic and Wildlife Resources (DAWR) at Fena Lake not open to the general public, people have wanted more areas available for freshwater fishing. The reservoir could serve as an excellent resource for aquatic education and providing an area to promote freshwater fishing. The project will enhance recreational sportfishing opportunities in Masso Reservoir through dredging of the reservoir, rehabilitation of the water control gate structure, construction of a cofferdam, and development of the area for public access and shoreline fishing.

The US Navy constructed the Masso Reservoir in the early 1940’s for use as a potable water reservoir. It was abandoned in 1951 because siltation had made it unsuitable for water storage. In 1978, the Black Construction Company, working under contract to DAWR, cleared about two acres of the pond by removing the Phragmites grass. At that time, the retaining wall, spillway and sluice gate were repaired. The pond was stocked numerous times with red hybrid tilapia (Oreochromis mossambica X O. nilotica), tucunare or “peacock bass” Chichla ocellaris and mosquito fish (Gambusia sp.) at a rate to keep a natural balance in the reservoir. Because of poaching, poisoning, and vandalism, the project was discontinued. In 1993 the restoration project was revived because the DAWR has increased it’s enforcement staff and was then able to use fish restoration funds for “put and take” fishing. Because the projected cost of the project is approximately $1,300,000, it will be completed in phases. The biological survey has been completed and engineering plans drawn for the restoration. A cofferdam will be constructed first, due to environmental considerations for the endangered common moorhen using the reservoir. During the second phase, the reservoir will be dredged and the reservoir made fishable. The third phase will complete the project with a floating wharf and fishing platform, plus parking and restroom facilities.

The Guam Land Use Commission has approved the Wetland permit for the Masso Reservoir restoration project. In addition, the 401 Water Quality Certification was granted by the Guam Environmental Protection Agency (GEPA). Two acres of acacia trees (Acacia sp.) have been planted on the adjacent Government of Guam property. Seeds of native species were collected to plant 4 additional acres in the watershed.

Masso Reservoir/Nature Trail Project:

To view proposal, click on: Guam-Pitii-MassoNCWPfinalproposal

Freshwater Monitoring

Freshwater Monitoring: native stream faunaRelated projects:Fena lake fish stocksIntroduced pest species [?]The watershed approach

On islands such as Guam, the land and the sea are intimately linked. Pollution and sediments from the land enter and damage the rivers, and the rivers carry the problems downstream to the reefs and fisheries. So, healthy reefs depend on healthy rivers, and healthy rivers depend on what is going on in the whole area around them–the watershed. [Pop-up: What is a watershed?]

Ylig River during heavy rains. Photo: C. Lobban

In order to maintain the quality of Guam’s watershed ecosystems, we first need to identify the aquatic species residing in these ecosystems, and to determine their densities, the physical characteristics of the streams, and the quality of the water. Wise watershed management — and ultimately the health of Guam’s coastal resources — depends on having these baseline data.

Although various watersheds have been monitored for different parameters, in general Guam’s freshwater resources are not well studied. There are several problems with the existing data. First, the methods of monitoring have seldom been replicated, making comparisons or management as a whole unrealistic. Second, in the past ten years the island has experienced a rapid economic growth and structural development. Some existing and proposed developments, such as golf courses/resorts, occupy large tracts of land with major watersheds. Third, much of the existing watershed work has been completed by off-island consultants over short intervals using techniques developed for temperate areas and not applicable in their entirety to Guam’s tropical freshwater systems. Overall, then, few baseline data exist by which to assess potential impacts of proposed development on streams, lakes, and coastal areas. Nevertheless, it is evident that some development projects initiated within the last 10 years have significantly degraded watershed quality. The impact of this on coral reef habitat is also evident.

The freshwater monitoring project of DAWR is designed to gather long-term, reliable data for watershed management. Species composition, organism density, and habitat characteristics were collected in the rivers identified as experimental and controls were chosen in FY97, using the methods described in the annual report of FY97. The experimental rivers, located above Fena Reservoir included: Almagosa; Maulap; and Sadog. These watersheds were selected because they represent a range of watershed characteristics that may help to determine the impacts of the present and proposed land uses. The control rivers include: Maagas; Manenggon; Pago; and Ylig. [The study was originally set up to look at the effects of the dam on the fauna–especially upstream migration, thus rivers below the dam were designated as controls, and those above the lake as experimental.

The project has a second aim, to heighten public interest in native species found in freshwater ecosystems and to develop a recreational fishery based on native species in Guam’s rivers. Knowledge of and interest in freshwater species is limited on Guam. To increase awareness of these important organisms and their habitats, educational materials, such as a field guide and posters, need to be developed. Additionally, some native species, such as the flagtail Kuhlia rupestris, are ideal candidates for a recreational fishery.

Current status[Table 1] Species distribution in experimental and control streams determined by visual surveys.A checkmark indicates the presence of a species and an empty cell indicates its absence. Experimental Streams Control StreamsSpecies Alamagosa Maulup Sadog Maagas Manenggon Pago YligAnguilla marmorata (eel)Awaous guamensis (goby)Clarias sp. (walking catfish)Eleotris fusca (sleeper goby)Kuhlia rupestris (flagtail)Macrobrachium lar (freshwater prawn)Oreochromis massambicus (tilapia)Stiphodon sp. (goby)Tilapia zillii (tilapia)

Four species were seen only in control streams. The dam probably excludes flagtails because it is not morphologically adapted for climbing. It is also absent above natural waterfalls in most streams of Guam. The Clarias or Walking catfish, which is an introduced species, may have also be impeded by the dam. Alternatively, sleeper gobies can scale waterfalls and are certainly under-represented in our visual surveys due to their cryptic nature. Tilapia zillii have been seen above the dam in previous surveys. The snail family Neritidae has not been seen above the dam since surveys began in 1996. However, they are not prevented from scaling vertical heights anatomically. One individual was seen on the spillway in 1996 and nerites have been seen above waterfalls in other streams. Species of nerites often exhibit rheotaxis and thus may terminate their upstream migration in the absence of a perceptible current dampened by the presence of the lake. Nerite numbers may also be reduced by predation. The exposed surface of the spillway may leave the nerites more vulnerable to predation by migratory shorebirds. During FY00, the ongoing monitoring of four previously selected watersheds continued. Faunal counts and habitat characteristics recorded in FY00 are summarized in the annual report. The influence of Fena Reservoir on migrating fauna continues to be assessed. The results of the FY97 study were used as baseline data in comparative analyses with data collected in FY12. Significantly fewer species per square meter were surveyed in FY12 than in FY97. Although mean species density was significantly higher in FY97 than in FY12, a greater number of species were seen in FY00 (9) than in FY97 (8). Additionally, the number of species per square meter has not differed significantly for the past 3 years. Significantly fewer individuals per square meter were also seen in FY00 than in FY97, but total density did not differ significantly for the past 2 years. Although four years of data collection is not enough time to see broad trends, total densities and species composition appears relatively consistent. As part of the education objective, a local artist was commissioned to create a poster showcasing the native freshwater fauna of Guam. The freshwater fauna poster was published in 2001. Details on the project can be found in the FY97 and FY12 annual reports, with a brief update for 2001.

Freshwater Pest

This specimen of Salvinia was obtained from a local vendor at a plant sale. Photo C. LobbanSalvinia and other nasty introduced weeds!!?? [not part of this project…]Apple snail…Comments on invasive alien species?


This page will include current research from Guam institutions and as well as the Micronesia region.