Offshore
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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.
Landings
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 | 64.6 |
| Bottomfishing | 13.4 |
| Spearfishing | 15.5 |
| Atulai night-light jigging | 0.3 |
| Other Methods | 4.5 |
| Total FY00 Offshore Catch | 98.3 |
Skipjack accounts for 45% of the trolling catch.
Photo: www.fishbase.org
[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 Species |
| Katsuwonus pelamis | 28,903 | 45 |
| Coryphaena hippurus | 9,268 | 14 |
| Thunnus albacares | 8,865 | 13 |
| Makaira mazara | 7,395 | 11 |
| Acanthocybium solandri | 6,856 | 10 |
| Elagatis bipinnulata | 965 | <2 |
| Euthynnus affinis | 858 | <2 |
| Sphyraena barracuda | 602 | <1 |
| Gymnosarda unicolor | 465 | <1 |
| Other species | 400 | <1 |
| Total |
64,577 |
100 |
Declining 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 .
Guam Comprehensive Wildlife Conservation Strategy, 9/27/2005
