Sustainable Fisheries and Fishing Communities

The Center carries out extensive activities to monitor U.S. fisheries throughout the Pacific Islands Region, assess the status of exploited fish stocks, and provide scientific advice to fishery managers. Fish catch and fishing effort are monitored by Center staff in collaboration with local government partners in American Samoa, CNMI, Guam, and Hawaii through the Western Pacific Fisheries Information Network. Research is conducted on fish life history and biology; mitigation of fishery interactions with protected species; fish population dynamics and stock assessment; economics and human dimensions of fisheries; and more. Substantial collaborative research on pelagic stocks is carried out through the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean. Monitoring information and stock assessments support the development and implementation of domestic fishery management plans for insular and pelagic fisheries through the Western Pacific Fishery Management Council. They also contribute to international management of fisheries for tunas, billfishes, and other highly migratory pelagic fish through the Western and Central Pacific Fisheries Commission and the Inter-American Tropical Tuna Commission. During 2011, progress was noted in several areas:

Circle Hook Research Aims at Reduction of Longline Fishery Bycatch

A key goal of NOAA is to find ways to sustain valuable fisheries for target species while reducing unwanted capture and incidental mortality of non-target species of fish and protected marine wildlife, such as turtles and seabirds. Research has shown that in pelagic longline fisheries, reductions in unwanted catch and related mortality can often be achieved by modifying the fishing gear and how it is deployed. In particular, circle hooks have been widely advocated as a way to reduce incidental take and mortality of sea turtles and have been successful in doing so in the Hawaii-based shallow-set swordfish longline fishery. But in studies across several longline fisheries, the effect of circle hooks on longline catch rates and survival of non-target fish species, such as marlins, have been variable.

In the Costa Rican longline fishery experiments, circle hooks with an appendage produced reduced catch rates of sea turtles and 
                   most other species groups.
In the Costa Rican longline fishery experiments, circle hooks with an appendage produced reduced catch rates of sea turtles and most other species groups.

PIFSC scientists in the Fisheries Interaction and Conservation Program recently completed a pair of experiments to evaluate circle hooks as a means to reduce unwanted catch in pelagic longline fisheries. The first experiment was a study in the Costa Rican longline fishery. The fishery targets mahimahi and sharks, but the catch is dominated by non-target species such as sea turtles and rays. Working in collaboration with other scientists, PIFSC researchers compared catch rates for target and non-target species on 2 kinds of hooks: regular circle hooks and experimental circle hooks bearing a wire appendage extending at an angle from the hook's eye. They found that the appendage circle hooks produced a lower catch-per-unit effort (CPUE) than the standard circle hooks for all species groups, except for rays; the differences were statistically significant for sea turtles and tunas and billfishes. The effectiveness of the appendage hooks in reducing turtle takes is encouraging, but further research is needed to find a solution that also maintains the economic viability of the fishery.

In the Hawaii tuna longline experiments, average catch rate of the target species, bigeye tuna, was slightly higher on circle 
                   hooks than on tuna hooks. For all other species, catchability on circle hooks was lower.
In the Hawaii tuna longline experiments, average catch rate of the target species, bigeye tuna, was slightly higher on circle hooks than on tuna hooks. For all other species, catchability on circle hooks was lower.

In a second study, PIFSC scientists conducted an experiment around the Hawaiian Archipelago to quantify effects of 3 types of hooks in the Hawaii-based tuna longline fishery: Japanese-style tuna hooks normally used by Hawaii longliners targeting bigeye tuna, J-hooks formerly used by Hawaii longliners targeting swordfish, and large (size 18/0) circle hooks currently required by Hawaii shallow-set swordfish boats. Scientific observers overseen by the NMFS Pacific Islands Regional Observer Program were deployed on 16 contracted tuna longliners to collect data under a well-planned experimental protocol. When setting their gear, some vessel captains attached circle hooks alternately with tuna hooks along the mainline, so that encounters of marine life with the 2 types of hooks used would be equally likely during the set; there were 1182 such sets. Other vessels alternately deployed circle hooks and J-hooks, resulting in 211 sets comparing these hook types.

Results showed no significant differences between hook types in the average catch rate of the target species, bigeye tuna. But for almost all non-target fish species, average catch rates on circle hooks were significantly lower than with tuna hooks. In the comparisons with J-hooks, average catch rates were higher on circle hooks for bigeye tuna and albacore, and lower for the other species. But for 10 of the 18 species, the differences in relative catchability were not statistically significant, largely due to the smaller number of comparisons. There were no differences between hook types in the average size of bigeye caught, but in general, billfishes caught on circle hooks were significantly longer than those caught on tuna hooks. For 6 species, the proportion of fish alive was significantly higher on circle hooks than on tuna hooks; indeed for 13 of the 18 species, the proportion of fish alive was lower on tuna hooks than either circle or J-hooks.

The experiment indicated that adoption of large circle hooks in the deep-set Hawaii tuna fishery for bigeye tuna could help achieve conservation goals by reducing incidental capture and mortality of billfishes, sharks and several other non-target fish species while maintaining catches of bigeye. Effects of such measures on the fleet's economic performance are uncertain. Revenues from bigeye tuna might increase; if the fish caught on circle hooks can be landed in better condition, they might command a higher ex-vessel price. On the other hand, revenues from marketed non-target species such as yellowfin tuna, opah, billfishes, and dolphinfish might be reduced unless the reduced market volumes are accompanied by higher ex-vessel prices; full economic impacts have not been assessed.

Findings from both studies were peer-reviewed and published in 2011. The Costa Rican research appeared in the journal Marine Biology [7] and the Hawaii longline fishery study was issued in Fisheries Research [8].

Socioeconomic Surveys Reveal Characteristics of Hawaii's Small Boat Pelagic Fishery

To craft effective fishery regulations, managers need a full understanding of economic and social dimensions of the fishery and fishing community. To provide such a foundation for management of Hawaii's pelagic fisheries, PIFSC scientists conducted a survey of costs and earnings in the small-boat pelagic fishing fleet. To measure seasonal variation, the survey was carried out in two segments, one during the summer of 2007 and the other during the winter of 2007-2008. Fishers were interviewed at boat ramps across the State of Hawaii as they returned from fishing excursions. In each interview, researchers gathered information on the fishing vessel used and its operating characteristics, fixed and variable costs associated with fishing and maintenance of the vessel, amount of fish caught, disposition of the catch, demographic characteristics of the participants, and more. The survey targeted motorized vessels under 40 ft, and excluded charter boats. Almost all vessels in the study made single-day or single-night trips.

Yellowfin tuna (ahi) are a favorite target of Hawaii's recreational fishermen.
Yellowfin tuna (ahi) are a favorite target of Hawaii's recreational fishermen.

Survey results enabled the research team to estimate the proportions of fishermen who were commercial fishers (those who sell fish) versus recreational (or non-commercial) fishers, based on the fishers' self-classification and their actual observed behavior. They also provided a statistical basis for characterizing each group of fishermen. Of the 343 interviewed fishers, 42% self-classified themselves as commercial fishermen, yet 60% of all respondents actually had sold fish in the past year. And about 30% of fishers who considered themselves as recreational had sold fish in the past year. Survey respondents reported making 55 fishing trips in the past year, on average; commercial fishers took significantly more trips than noncommercial fishermen. Commercial trips were also longer than recreational trips, but did not cost significantly more. About 47% of fishers reported using more than one type of fishing gear during the past year. Pelagic fish accounted for about 80% of the previous year's total catch and fuel costs made up 66% of average pelagic fishing trip expenditures. Average gross revenues of commercial fishers just defrayed their annual costs; few fishermen profited from fishing. Most respondents said they sold their catch to cover trip expenses, and that profit was not their primary motive for fishing. On average, only 19% of personal income of commercial fishers resulted from fishing.

Small-boat fishers landed 3.4 million pounds of fish in 2006, generating revenues of $6.8 million. Almost all fishers appeared to participate in a fish sharing network with friends and relatives and more than 62% considered their catch to be an important source of food for their family. Although most of the commercial catch was sold to Hawaii restaurants and retail outlets, 38% was consumed by fishers and their families and shared with friends. The research team concluded that a simple classification of small-boat fishers into commercial and recreational categories is an insufficient basis for management analysis; managers should take into account the various cultural motivations that govern participation in the fishery and disposition of the catch.

The survey results were published in a Center technical report [9].

Tagging Study Measures Post-release Survival of Oceanic Sharks

In the Hawaii-based longline fisheries targeting tuna and swordfish, some sharks are also kept for sale, but most are discarded. Managers taking an ecosystem-based approach to management of the fishery need to take into account the bycatch mortality—the probability that fish caught but released alive by fishermen will subsequently die as a result of capture. Such information is particularly needed for sharks, given their key role as top-level predators in the ecosystem. In a recent study led by researchers at PIFSC, important progress was made in understanding post-release mortality of pelagic sharks caught by longline gear.

Pop-up tags were placed on pelagic sharks, like this oceanic whitetip, to study their likelihood of survival after release.
Pop-up tags were placed on pelagic sharks, like this oceanic whitetip, to study their likelihood of survival after release.

In the study, a research team analyzed data from pop-up satellite archival tags (PSATs) placed on 71 sharks caught and released in the central Pacific Ocean. The sharks represented five pelagic species: blue shark, shortfin mako shark, silky shark, oceanic whitetip shark, and bigeye thresher shark. The tags were deployed during research expeditions by the NOAA Ships Townsend Cromwell and Oscar Elton Sette from 2001 to 2006. Most fish were caught at depths less than 100 m, hoisted aboard the vessels in a sling, then tagged and released; bigeye threshers were tagged while in the water alongside the vessel, using a harpoon. The PSATS were programmed to record information on water temperature and depth every 15-60 minutes and to release from the fish and pop up to the sea surface after 8-13 months of deployment. Tags would also release if the tag remained at a constant depth (indicating tag loss) or sank below 1200 m and remained there longer than 15 minutes (implying fish mortality). After surfacing, tags transmitted their data payload to ARGOS computers via satellite.

PSAT data showed that the 5 species occupied different but overlapping oceanic habitats with respect to depth and temperature. Moreover, vertical migration patterns varied temporally and spatially among individual sharks. These patterns were affected by oceanographic phenomena, such as El Niño-Southern Oscillation. The species can be grouped broadly based on their daytime preferred temperature range as follows: silky sharks and oceanic whitetip sharks (both epipelagic species) spent 95% of their daylight hours in waters within 2 °C of the sea surface temperature; blue sharks and shortfin mako sharks (both mesopelagic-I species) spent 95% of their time in waters ranging between 9.7 ° C and 26.9 °C, and 9.4 ° C and 25.0 ° C, respectively; bigeye thresher sharks (a mesopelagic-II species) spent 95% of their time in water between 6.7 °C and 21.2 °C. The PSAT data also suggested that the epipelagic species occupied particular thermal niches depending on their body size and latitude.

Of the 71 PSATs deployed in this study, 44 popped off and reported data, including 16 on blue sharks. Only one of the 44 reporting tags indicated mortality of the fish, and that was on a blue shark. Combining data for the 16 reporting blue shark tags in this study and 62 others in previously published reports, a summary estimate of post-release mortality for blue sharks was calculated at 15% (with a 95% confidence interval of 8.5-25.1%). This result, and the apparent absence of post-release mortality for other species in this study (28 reporting PSATs), suggests that catch-and-release can be a viable strategy for reducing incidental mortality of sharks in longline fisheries.

The study was published in the peer-reviewed journal Fishery Bulletin [10].