Pelagic Longline Fishing Gear: A Brief History and Review of Research Efforts to Improve Selectivity

Pelagic longline gear had several independent evolutions, but the most widespread form appears to have been originally developed by the Japanese as early as the mid-19th century. Technological developments such as polyamide monofilament line and modern fishing vessel construction have resulted in the evolution and expansion of this gear type as the primary worldwide method of commercially harvesting large pelagic fishes such as broadbill swordfish and tunas.Although the adaptability of the gear through changes in materials, lengths, and deployment strategies has resulted in generally high selectivity for many target species, the bycatch of protected species by pelagic longlines is considered a global problem in the conservation effort to sustain populations of sea turtles, sea birds, and some istiophorid billfishes (sailfishes; spearfishes; marlins). Recent research on the modification of pelagic longline fishing strategies uses this inherent adaptability of the gear to avoid or reduce the mortality of bycatch species. This is an alternative to the traditional management strategy of closed areas, which fishermen view as less effective and generally more restrictive (limiting) with respect to target catches. This work with academic partners and commercial fishermen has resulted in the development of bycatch reduction strategies which include safe handling and release gear and protocols, use of circle hooks in place of traditional J-style hooks, restrictions on gangion and mainline lengths, and corrodible hooks

First Observations on the Re-Established Southeast Florida Recreational Swordfish Tournament Fishery

Recreational tournaments for swordfish (Xiphias gladius) existed in the Florida Straits between 1977 and 1983 before disappearing due to low catch rates and an overexploitation of the stock. The first recent swordfish tournament occurred in 2001 off southeast Florida with 13 participating vessels. In 2002, three swordfish tournaments were observed and anglers were interviewed to determine catch and gear characteristics of the re-established recreational fishery. A total of 156 vessels participated in these three tournaments, catching 112 swordfish and hooking an additional 48 animals. The combination of the recovery of the North Atlantic swordfish stock and the continuation of the 2001 closure of the Florida Straits to commercial pelagic longline fishing gear is expected to result in the continued expansion of the southeast Florida recreational swordfish fishery

Survival of White Marlin (Tetrapturus albidus) Released from Commercial Pelagic Longline Gear in the Western North Atlantic

To estimate postrelease survival of white marlin (Tetrapturus albidus) caught incidentally in regular commercial pelagic longline fishing operations targeting swordfish and tunas, short-duration popup satellite archival tags (PSATs) were deployed on captured animals for periods of 5-43 days. Twenty (71.4%) of 28 tags transmitted data at the preprogrammed time, including one tag that separated from the fish shortly after release and was omitted from subsequent analyses. Transmitted data from 17 of 19 tags were consistent with survival of those animals for the duration of the tag deployment. Postrelease survival estimates ranged from 63.0% (assuming all nontransmitting tags were evidence of mortality) to 89.5% (excluding nontransmitting tags from the analysis). These results indicate that white marlin can survive the trauma resulting from interaction with pelagic longline gear, and indicate that current domestic and international management measures requiring the release of live white marlin from this fishery will reduce fishing mortality on the Atlantic-wide stock

Post-Release Survival of Sailfish (Istiophorus platypterus) Captured on Commercial Pelagic Longline Gear in the Southern Gulf of Mexico

To estimate post-release survival of sailfish caught incidentally to regular commercial pelagic longline fishing operations in the southern Gulf of Mexico targeting mixed swordfish and tunas, ten pop-up satellite archival tags were deployed for ten days on incidentally captured animals. All ten tags transmitted following the full deployment period, transmitting 25-82% of the archived data. Repeated, short-duration movements at depth and horizontal displacement data from were consistent with survival of those nine of the ten animals for the ten-day deployment period. The results of this study indicate that sailfish can survive the trauma resulting from interaction with pelagic longline gear and that management measures promoting the release of sailfish from the pelagic longline fishery will reduce fishing mortality on the Atlantic sailfish stocks

Age and Growth of Three Coastal-Pelagic Tunas (Actinopterygii: Perciformes: Scombridae) in the Florida Straits, USA: Blackfin Tuna, Thunnus atlanticus, Little Tunny, Euthynnus alletteratus, and Skipjack Tuna, Katsuwonus pelamis

Background. Understanding the life history of a species is essential for fully understanding its role within an ecosystem. However, many of the fish species of high ecological value have not been studied due to their less prominent roles in local recreational and commercial fisheries in comparison to other targeted species. These valuable fishes are also important trophic linkages between small neritic fishes and large, economically valuable apex predators. This study describes for the first time the yearly age and growth patterns of three small tuna species inhabiting South Florida (USA) waters: blackfin tuna, Thunnus atlanticus (Lesson, 1831); little tunny, Euthynnus alletteratus (Rafinesque, 1810); and skipjack tuna, Katsuwonus pelamis (Linnaeus, 1758). Materials and methods. Tuna specimens were collected in two ways: via donations obtained from various fishing tournaments and charter captains in the areas of the Florida Straits as well as hook-and-line catches performed especially for this project. Age determination was based on sagittal otolith hyaline deposition patterns. Marginal increment analysis was used as an indirect validation method. Growth parameters were determined by comparison of the fish fork length and the hyaline band measurements. Results. Two hyaline bands formed each year in all three species—one in winter and one in summer. The von Bertalanffy growth equation produced a growth rate for each species: blackfin tuna, L∞ = 95.34 cm, K = 0.28, and t0 = –1.53; little tunny, L∞ = 77.93 cm, K = 0.69, and t0 = –0.69; and skipjack tuna, L∞ = 112.76 cm, K = 0.24, and t0 = –1.70. Parameters of each resulting von Bertalanffy equation were compared among species showing that little tunny grew the fastest, but skipjack had the largest estimated size. Results were also compared with growth rates currently used in stock assessments by fisheries management organizations, such as the International Commission for the Conservation of Atlantic Tunas (ICCAT). Conclusion. Sectioned otoliths indicate two bands a year for these three species in the Florida Straits. Results were comparable to other studies, with a similar finding of two bands per year in hard parts for these species. Further knowledge of these populations will aid in stock assessments for these species and the ongoing shift to ecosystem-based management plans

Habitat Utilization and Vertical Distribution of the Great Barracuda Sphyraena barracuda (Edwards 1771) in the Western North Atlantic Using Electronic Archival Tags

The Great Barracuda Sphyraena barracuda is a large predatory teleost commonly seen in the tropics of the Western North Atlantic. Using pop-up satellite archival tags (PSATs), two large Great Barracuda (101 and 104 cm FL) were tagged off South Florida for a 15-day deployment period. Great Barracuda 88094 traveled 471 km minimum straight-line distance (MSLD) over the deployment duration, while Great Barracuda 88095 traveled 1231 km MSLD. Great barracuda 88094 achieved a maximum depth of 145.2 m, while 88095 to a maximum depth of 186.9 m, although such movements were for short time durations. The data obtained indicate significant differences in diel behavior, with both individuals utilizing deeper depths during nighttime periods. The results of this study show that great barracuda are capable of travelling great distances over short periods of time, with short-duration movements to depths greater than 100 meters

Effects of Circle Versus J-style Hooks on Target and Non-Target Species in a Pelagic Longline Fishery

The U.S. Atlantic coastal pelagic longline fishery that targets tunas and swordfish also interacts with a wide range of non-target species including billfishes and sea turtles. Preliminary studies indicate that a change in terminal gear from J-style hooks to circle hooks may reduce bycatch mortality, but the effects of this change on catch rates of target species are unclear. To evaluate this, we monitored catch composition, catch rates, hooking location, and number of fish alive at haulback during 85 sets in the fall and spring seasonal fisheries from a commercial vessel operating in the western North Atlantic. Circle (size 16/0, 0° offset) and J-style (size 9/0, 10° offset) hooks were deployed in an alternating fashion. Hook–time recorders were used to assess time at hooking and temperature–depth recorders to measure gear behavior. Catch rates for most species categories were not significantly different between hook types (P \u3c 0.05), although circle hooks generally had higher tuna catch rates in the fall and lower swordfish catch rates in the spring. In the fall, both total catches and catches of pelagic rays were significantly higher on J-style hooks. Yellowfin tuna in the fall and dolphinfish in the spring caught on circle hooks were significantly larger than those caught on J-style hooks. In both seasonal fisheries, circle hooks caught fishes in the mouth more frequently than J-style hooks, which hooked more often in the throat or gut, although these differences between hook types were not statistically significant. Yellowfin tuna in the fall fishery were over four times more likely to be hooked in the mouth with circle hooks than with J-style hooks. Several target and bycatch species showed higher rates of survival at haulback with circle hooks, although only for dolphinfish in the fall fishery was this difference statistically significant. Our results suggest that the use of 0° offset circle hooks in the coastal pelagic longline fishery will increase the survival of bycatch species at haulback with minimal effects on the catches of target species

Length-Length and Length-Weight Relationships of Oilfish (Ruvettus pretiosus), Escolar (Lepidocybium flavobrunneum), Snake Mackerel (Gempylus serpens), and Longnose Lancetfish (Alepisaurus ferox) From the Gulf of Mexico and the Western North Atlantic Ocean

Oilfish, escolar, snake mackerel (order Aulopiformes, family Gempylidae), and longnose lancetfish (order Perciformes, family Alepisauridae) sampled from the western North Atlantic and the Gulf of Mexico were analyzed for length–weight and length–length relationships. These species are encountered as occasional bycatch of pelagic longline fisheries. The fish (161 specimens, 19.0–149.1 cm TL) were collected over a 3-year period (January 2007–January 2010) from pelagic longline gear targeting swordfish and tuna. For each species, 95% confidence limits (CI) of parameters b and log a and regression coefficients (r2) were calculated for log-transformed length–weight relationships. The length–weight parameter b for all species ranged from 2.881 to 3.358, with regression coefficients (r2) ranging from 0.75 to 0.98. Linear relationships between fork lengths, standard lengths, and total lengths were also calculated