Longline Gear Research Articles

Deepwater Horizon Oceanic Fish Restoration Project: An application of market mechanisms for conservation

Deepwater Horizon in 2010 marked the largest oil spill in United States history. Following the spill, a council of federal and state trustees was established to assess the impact of the released oil on natural resources in the Gulf of Mexico. The Programmatic Damage Assessment and Restoration Plan developed by the trustees specifically called for restoration approaches that would directly reduce known sources of mortality by providing fishing communities with tools and incentives to limit impacts on fishery resources. The first project selected to restore a portion of the injuries sustained by pelagic fishes, the Deepwater Horizon Oceanic Fish Restoration Project, was developed by the National Oceanic and Atmospheric Administration to reduce bycatch in the Gulf of Mexico Highly Migratory Species fishery. Participating vessel owners are compensated to voluntarily refrain from using pelagic longline gear for the first six months of the year, and are encouraged to adopt alternative fishing gear that results in low bycatch mortality. This paper describes the various mechanisms considered, posted-price offer, pay-as-bid auction, and uniform-price auction, leading to the design of the compensation for both the repose and alternative gear components of the Deepwater Horizon Oceanic Fish Restoration Project, and draws lessons from the first two years of the project's implementation.

Dynamic Simulation of Pelagic Longline Retrieval

To improve fishing gear efficiency, it is important to understand the interactions among sea current, fishing vessel, line hauler, and catches during pelagic longline gear retrieval. In this study, fishing gear configuration parameters, operational parameters, and 3D ocean current data were collected from Indian Ocean. Dynamic models of pelagic longline gear retrieval were built using the lumped mass method and solved using the Euler-Trapezoidal method. From the results, the pulling force of line hauler exerted on the gear was 2800–3600 N. There were no significant differences (P > 0.05) between the time of the hook retrieval measured at sea and that obtained from the simulation. The absolute values of the movement velocity at representative nodes along the X, Y, and Z axes were 0.01–25.5 m s−1. These results suggest that the dynamic model of longline fishing gear retrieval can be used to analyze the interactions among sea current, fishing vessel, line hauler, longline gear, and catches, and to acquire the basic data for optimizing the design of the line hauler. Moreover, the model can serve as a reference to study the hydrodynamic performance of other fishing gears during the hauling process.

Applications of the longline simulator (LLSIM) using US pelagic longline logbook data and Atlantic blue marlin

Spatiotemporal variability in fishing patterns and species distributions from ocean climatology confound analysis of pelagic longline CPUE. A generalized computer program, LLSIM, was developed to simulate such data to test methods used to quantify abundance trends. The method employs a Monte-Carlo algorithm with a probability of capture computed for each hook on each set based on overlaps of the species- and hook-depth distributions. The method was tested using characteristics of the longline gears and fishing locations of the US pelagic longline fleet and blue marlin latitude-longitude-depth distributions predicted using a species distribution model fitted to 1986–2012 monthly oceanographic data. Catch data were simulated for two hypothetical trends in total abundance. The simulator was capable of performing complex but controlled simulation experiments. Analyses demonstrated the advantage of comparing estimates from alternative standardizations to known true values that are not possible with real data.

Migrations and habitat use of the smooth hammerhead shark (Sphyrna zygaena) in the Atlantic Ocean.

The smooth hammerhead shark, Sphyrna zygaena, is a cosmopolitan semipelagic shark captured as bycatch in pelagic oceanic fisheries, especially pelagic longlines targeting swordfish and/or tunas. From 2012 to 2016, eight smooth hammerheads were tagged with Pop-up Satellite Archival Tags in the inter-tropical region of the Northeast Atlantic Ocean, with successful transmissions received from seven tags (total of 319 tracking days). Results confirmed the smooth hammerhead is a highly mobile species, as the longest migration ever documented for this species (> 6600 km) was recorded. An absence of a diel vertical movement behavior was noted, with the sharks spending most of their time at surface waters (0–50 m) above 23°C. The operating depth of the pelagic longline gear was measured with Minilog Temperature and Depth Recorders, and the overlap with the species vertical distribution was calculated. The overlap is taking place mainly during the night and is higher for juveniles (~40% of overlap time). The novel information presented can now be used to contribute to the provision of sustainable management tools and serve as input for Ecological Risk Assessments for smooth hammerheads caught in Atlantic pelagic longline fisheries.

Comparative Abundance, Species Composition, and Demographics of Continental Shelf Fish Assemblages throughout the Gulf of Mexico

AbstractWe analyzed the results of the first comprehensive, systematic, fishery‐independent survey of Gulf of Mexico (GoM) continental shelves using data collected from demersal longline sampling off the United States, Mexico, and Cuba. In total, 166 species were sampled from 343 longline sets during 2011–2017, which deployed 153,146 baited hooks, catching 14,938 fish. Abundance, species richness, and Shannon–Wiener diversity indices by station were highest in mid‐shelf depths (~100 m), declining by about half in deeper waters. Six spatial assemblages were identified by testing the results of cluster analysis using similarity profile analysis and then plotting the geographic location of identified station clusters. A high degree of depth‐related and horizontal zonation was evident for demersal fish species. Multispecies CPUE (number per 1,000 hook‐hours) was highest off the north‐central (NC) and northwestern (NW) GoM and lower on the West Florida Shelf (WFS), Cuba (CUB), Yucatan Peninsula (YP), and southwestern (SW) GoM. Snappers and groupers were most abundant in the WFS and CUB, while elasmobranchs were the dominant taxa in the NC and NW GoM. Pelagic species were relatively rare everywhere (owing to the use of demersal longline gear), but were most dense off CUB. Species richness was highest in the NC and WFS subareas and lowest in the NW and CUB. Slopes of multispecies size spectra, which integrated mortality, recruitment, growth, and species interactions among size‐groups, were shallowest in the NW and NC GoM and steepest off the WFS and YP. These results provide a basis for evaluating the relative resiliency potential of species assemblages across the continental shelves of the GoM, and thus for identifying subareas that are most vulnerable to acute and chronic perturbations from cumulative effects of fishing, climate change, pollution (including oil spills), habitat loss, and invasive species.

Greenland shark (Somniosus microcephalus) feeding behavior on static fishing gear, effect of SMART (Selective Magnetic and Repellent-Treated) hook deterrent technology, and factors influencing entanglement in bottom longlines.

The Greenland Shark (Somniosus microcephalus) is the most common bycatch in the Greenland halibut (Reinhardtius hippoglossoides) bottom longline fishery in Cumberland Sound, Canada. Historically, this inshore fishery has been prosecuted through the ice during winter but winter storms and unpredictable landfast ice conditions since the mid-1990s have led to interest in developing a summer fishery during the ice-free season. However, bycatch of Greenland shark was found to increase substantially with 570 sharks captured during an experimental Greenland halibut summer fishery (i.e., mean of 6.3 sharks per 1,000 hooks set) and mortality was reported to be about 50% due in part to fishers killing sharks that were severely entangled in longline gear. This study investigated whether the SMART (Selective Magnetic and Repellent-Treated) hook technology is a practical deterrent to Greenland shark predation and subsequent bycatch on bottom longlines. Greenland shark feeding behavior, feeding kinematics, and variables affecting entanglement/disentanglement and release are also described. The SMART hook failed to deter Greenland shark predation, i.e., all sharks were captured on SMART hooks, some with more than one SMART hook in their jaw. Moreover, recently captured Greenland sharks did not exhibit a behavioral response to SMART hooks. In situ observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25–35 cm. This method of feeding is suggested to negate the potential deterrent effects of electropositive metal and magnetic alloy substitutions to the SMART hook technology. The number of hooks entangled by a Greenland shark and time to disentangle and live-release a shark was found to increase with body length.

Using autonomous video to estimate the bottom-contact area of longline trap gear and presence–absence of sensitive benthic habitat

Bottom longline hook and trap fishing gear can potentially damage sensitive benthic areas (SBAs) in the ocean; however, the large-scale risks to these habitats are poorly understood because of the difficulties in mapping SBAs and in measuring the bottom-contact area of longline gear. In this paper, we describe a collaborative academic–industry–government approach to obtaining direct presence–absence data for SBAs and to measuring gear interactions with seafloor habitats via a novel deepwater trap camera and motion-sensing systems on commercial longline traps for sablefish (Anoplopoma fimbria) within SGaan Kinghlas – Bowie Seamount Marine Protected Area. We obtained direct presence–absence observations of cold-water corals (Alcyonacea, Antipatharia, Pennatulacea, Stylasteridae) and sponges (Hexactinellida, Demospongiae) at 92 locations over three commercial fishing trips. Video, accelerometer, and depth sensor data were used to estimate a mean bottom footprint of 53 m2 for a standard sablefish trap, which translates to 3200 m2 (95% CI = 2400–3900 m2) for a 60-trap commercial sablefish longline set. Our successful collaboration demonstrates how research partnerships with commercial fisheries have potential for massive improvements in the quantity and quality of data needed for conducting SBA risk assessments over large spatial and temporal scales.

The development of length-weight relationships for four pelagic fish species in the tropical Northwest Pacific Ocean

The present study provides the length–weight relationships (LWRs) for four pelagic fish species belonging to three families sampled with the longline gear from the tropical Northwest Pacific Ocean. The sampling was conducted by the Chinese longline observers from June 2011 to September 2012 and the fishes were captured by commercial pelagic longline fleets. The circular size 4.0 sun-C-37 Japanese tuna hook design was used for this fishing operation. Length–weight relationship for one of these species is unknown to Fish Base. Additionally, a new maximum length of one fish species is identified in the study.

Estimation of tuna longline hook depth for improved performance in Fiji

In pelagic longline, deploying the gear such that the depth of the hook is the same as that of the target fish is important to improve the fishing performance and selectivity. In this study, the depth of the tuna longline hook was estimated using the mass-spring model, catenary curve method, and secretariat of the pacific commission Pythagorean method in order to improve the performance of the longline gear in Fiji. The former two methods were estimated to be relatively accurate, and the latter showed a large error. Further, the mass-spring model accounted for the influence of tidal current in the ocean, which was found to be appropriate for use in field trials.

Fishery-specific solutions to seabird bycatch in the U.S. West Coast sablefish fishery

Abstract Bird scaring lines (BSLs) protect longline fishing gear from seabird attacks, save bait, reduce incidental seabird mortality and are the most commonly prescribed seabird bycatch mitigation measure worldwide. We collaborated with fishermen to assess the efficacy of applying BSL regulations from the demersal longline sablefish fishery in Alaska to a similar fishery along the U.S West Coast. In contrast to Alaska, some U.S. West Coast vessels use floats along the line to keep hooks off the seafloor, where scavengers degrade the bait and the target catch. Our results confirmed that BSL regulations from Alaska were sufficient to protect baits from bird attacks on longlines without floats, but not baits on longlines with floats. Longlines with floats sank below the reach of albatrosses (2 m depth) at a distance astern (157.7 m ± 44.8 95% CI) that was 2.3 times farther than longlines without floats (68.8 m ± 37.8 95% CI). The floated longline distance was well beyond the protection afforded by BSLs, which is approximately 40 m of aerial extent. Black-footed albatross attacked floated longlines at rates ten times more (2.7 attacks/1000 hooks, 0.48–4.45 95%CI) than longlines without floats (0.20 attacks/1000 hooks, 0.01–0.36 95% CI). Retrospective analysis of NOAA Fisheries Groundfish Observer Program data suggested that seabird bycatch occurs in a few sablefish longline fishing sectors and a minority of vessels, but is not confined to larger vessels. Analysis also confirmed fishermen testimonials that night setting reduced albatross bycatch by an order of magnitude compared to daytime setting, without reducing target catch. Night setting could be an effective albatross bycatch prevention practice if applied to the U.S. West Coast sablefish longline fishery and provide a practical alternative for vessels that elect to use floated longlines. These results highlight the importance of understanding region-specific longline gear modifications to identify effective bycatch reduction tools and the value of working collaboratively with fishermen to craft solutions.

Effectiveness of tori line use to reduce seabird bycatch in pelagic longline fishing.

Industrial longline fisheries cause the death of large numbers of seabirds annually. Various mitigation measures have been proposed, including the use of tori lines. In this study the efficiency of a single tori line to reduce seabird bycatch was tested on pelagic longline vessels (25-37m length). Thirteen fishing trips were carried out in the area and season of the highest bycatch rates recorded in the southwest Atlantic (2009–2011). We deployed two treatments in random order: sets with a tori line and without a tori line (control treatment). The use of a tori line significantly reduced seabird bycatch rates. Forty three and seven birds were captured in the control (0.85 birds/1,000 hooks, n = 49 sets) and in the tori line treatment (0.13 birds/1,000 hooks, n = 51 sets), respectively. In 47% of the latter sets the tori line broke either because of entanglement with the longline gear or by tension. This diminished the tori line effectiveness; five of the seven captures during sets where a tori line was deployed were following ruptures. Nine additional trips were conducted with a tori line that was modified to reduce entanglements (2012–2016). Seven entanglements were recorded in 73 longline sets. The chance of a rupture on these trips was 4% (95% c.l. = 1–18%) of that during 2009–2011. This work shows that the use of a tori line reduces seabird bycatch in pelagic longline fisheries and is a practice suitable for medium size vessels (~25-40m length). Because the study area has historically very high bycatch rates at global level, this tori line design is potentially useful to reduce seabird bycatch in many medium size pelagic longline vessel fishing in the southern hemisphere.

Mitigating bycatch in tuna fisheries

Monitoring and managing fisheries bycatch is increasingly recognized as a critical component of robust fisheries management frameworks. This review, addressing this subject, begins by defining bycatch and analyzing the reasons it happens, from accidental to intentional discarding. It identifies the most common species composing bycatch of the main tuna fisheries using purse seine and longline gear. Considerations of options available to estimate bycatch, their potential biases and uncertainties, and ways to address these issues are discussed. The formulas used to estimate bycatch also point to the options to reduce them, lowering bycatch per unit of effort or lowering effort itself. It shows that a mean can be reduced by reducing all its component figures, or by eliminating the high values at the extreme of the distribution (i.e., where a small proportion of events causes a large proportion of the problem), a common issue in bycatch. A generic strategy is described that can be applied to all gears and fisheries, and it is then described for the fisheries of interest, showing examples of its application. These cover many mitigation actions based on gear and operational changes. Management options aiming at reducing bycatch are also mentioned. A detailed description of the ways the strategy has been implemented for purse seiners and longliners is provided. Finally, market strategies, education and awareness of stakeholders, mainly fishers, and some potential future developments are briefly described.

Diurnal patterns in Gulf of Mexico epipelagic predator interactions with pelagic longline gear: implications for target species catch rates and bycatch mitigation

Bycatch in pelagic longline fisheries is of substantial international concern, and the mitigation of bycatch in the Gulf of Mexico has been considered as an option to help restore lost biomass following the 2010 Deepwater Horizon oil spill. The most effective bycatch mitigation measures operate upon a differential response between target and bycatch species, ideally maintaining target catch while minimizing bycatch. We investigated whether bycatch vs target catch rates varied between day and night sets for the United States pelagic longline fishery in the Gulf of Mexico by comparing the influence of diel time period and moon illumination on catch rates of 18 commonly caught species/species groups. A generalized linear model approach was used to account for operational and environmental covariates, including: year, season, water temperature, hook type, bait, and maximum hook depth. Time of day or moon phase was found to significantly alter catch rates for 88% of the taxa examined. Six taxa—swordfish (Xiphias gladius Linnaeus, 1758); tiger shark (Galeocerdo cuvier Peron and Lesueur, 1822); silky shark (Carcharhinus falciformis Muller and Henle, 1839); oilfish (Ruvettus pretiosus Cocco, 1833); bigeye thresher shark (Alopias superciliosus Lowe, 1841); and escolar (Lepidocybium flavobrunneum Smith, 1843)—exhibited higher catch rates at night, while eight taxa—skipjack tuna (Katsuwonus pelamis Linnaeus, 1758); wahoo (Acanthocybium solandri Cuvier, 1832); white marlin [Kajikia albida (Poey, 1860]; dolphinfish (Coryphaena sp.); yellowfin tuna (Thunnus albacares Bonnaterre, 1788); rays (Pteroplatytrygon violacea Bonaparte, 1832, Mobulidae sp.); lancetfish (Alepisaurus sp.), and blue marlin (Makaira nigricans Lacepede, 1802)—had higher daytime catch rates. These results reveal that shifts in effort between daytime and nighttime fishing (which are highly correlated with shifts between yellowfin tuna and swordfish targeting strategies) could have substantial, species-specific effects on bycatch rates. Whether driven by fishery conditions, market influences, or management measures, such temporal shifts in the timing of pelagic longline sets may have important implications for species-specific conservation goals and warrant further consideration.

Sink or swim? Factors affecting immediate discard mortality for the gulf of Mexico commercial reef fish fishery

Fishery observer data collected from June 2006 through December 2015 in the Gulf of Mexico commercial reef fish fishery were examined to determine if any covariates available affected immediate discard mortality for six species: red grouper Epinephelus morio, red snapper Lutjanus campechanus, vermilion snapper Rhomboplites aurorubens, gag grouper Mycteroperca microlepis, scamp grouper Mycteroperca phenax, and speckled hind Epinephelus drummondhayi. Using logistic regression models, this study predicted immediate discard mortality was positively correlated with increased depths, seasons associated with warmer water temperatures, and external evidence of barotrauma. Additionally, bottom longline gear increased the predicted probability of immediate mortality compared to vertical line gear for all species except vermilion snapper. Air bladder venting significantly decreased the predicted probability of immediate mortality for all species except speckled hind. Future research incorporating tag-recapture data into the current observer program for the commercial reef fish fishery is vital to assess if condition assessment at release can be relied on as an accurate proxy for long-term survival. This research provides information that managers could potentially use to make more informed decisions when implementing measures such as changes to existing size limits, venting requirements, and seasonal, area, or gear restrictions intended to reduce unwanted discard mortality.

Tailoring Ecological Monitoring to Individual Marine Reserves: Comparing Longline to Hook‐and‐Line Gear to Monitor Fish Species

AbstractFishery‐independent hook‐and‐line surveys are currently being used to assess marine reserve performance in California and Oregon using a regionally standardized approach. Catch compositions generated from these hook‐and‐line surveys (pole‐and‐line gear) at Oregon's southernmost marine reserve were compared with local commercial landing data. Several species present in the commercial catch were undersampled in the marine reserve hook‐and‐line dataset, including China Rockfish Sebastes nebulosus, Vermilion Rockfish S. miniatus, Quillback Rockfish S. maliger, Copper Rockfish S. caurinus, and Cabezon Scorpaenichthys marmoratus. We conducted a gear selectivity study to explore whether modified commercial long‐lining gear could supplement current hook‐and‐line efforts. Both gear types were fished simultaneously from a single vessel inside and outside of the reserve. Species composition, catch rate, size distribution, and fish condition between the two gear types were compared. Catch composition differed significantly between longline and hook‐and‐line gear. Catch rates of nearshore rocky reef fish species were higher for longline than hook‐and‐line gear for all but two species. Importantly, higher catch rates were significant for three of the species of interest (Cabezon, Vermilion Rockfish, and Copper Rockfish). For four different species, larger individuals were caught on the longline compared with the hook‐and‐line gear. Incidence of predation and mortality were higher with long‐lining but limited to three species groups: Black Rockfish S. melanops, Blue Rockfish S. mystinus and Deacon Rockfish S. diaconus complex, and Canary Rockfish S. pinniger. Symptoms of barotrauma were higher with hook‐and‐line gear. We demonstrated that longline gear can be used to catch and release species targeted by the local fishery and used simultaneously with hook‐and‐line gear from a single vessel to broaden both the species and the size ranges sampled. These results underscore the need to consider regionally standardized long‐term monitoring approaches in conjunction with locally tailored efforts to generate data for detecting marine reserve effects at both local and regional scales.

Influence of bait type on catch rates of predatory fish species on bottom longline gear in the northern Gulf of Mexico

Influence of bait type on catch rates of predatory fish species on bottom longline gear in the northern Gulf of Mexico

Characterizing loggerhead sea turtle, <I>Caretta caretta</I>, bycatch in the US shark bottom longline fishery

Sea turtle bycatch in longline fishing gear is an ongoing threat to the recovery of sea turtle populations. While considerable research has focused on pelagic longline fisheries, very little attention has been paid to captures of sea turtles in bottom longlines. Estimates of sea turtle takes in the shark bottom longline fishery have raised concern that this fishery may be impacting loggerhead sea turtle, Caretta caretta (Linnaeus, 1758), populations. However, there are no current management actions designed to reduce the bycatch of sea turtles in fisheries that target sharks using bottom longline gear because no studies have identified which factors, if any, influence the capture of a loggerhead sea turtle. We used generalized linear models to determine which factors influence the probability of loggerhead sea turtle captures in the shark bottom longline fishery, and which factors are related to at-vessel mortality. While a variety of fishing techniques were considered as factors, no particular fishing method was found to predict a capture of a sea turtle. The most significant factor in predicting the capture of a loggerhead sea turtle in shark bottom longline gear was the area fished. Soak time was found to predict at-vessel hooking mortality with the median time for a mortality to occur was 14–15 hrs. While no definitive fishing factor was identified in the capture or mortality of a loggerhead sea turtle, research is needed using controlled methods for further examining the factors affecting captures of sea turtles in this and other bottom longline fisheries.

Combined stomach content and δ13C/δ15N analyses of oilfish, escolar, snake mackerel and lancetfish in the western North Atlantic

AbstractLarge, mesopelagic teleost fishes have a potentially keystone position in the ecology of the pelagic water column, yet remain relatively unstudied when compared with large, commercially important, epipelagic fishes. Here, the ecological roles of four, large, vertically migrating teleosts were examined. Stomach content analyses were performed on 48 oilfish (Ruvettus pretiosis), 35 escolar (Lepidocybium flavobrunneum), 32 snake mackerel (Gempylus serpens) and seven lancetfish (Alepisaurus spp.) collected from pelagic longline gear in the Western North Atlantic Ocean from 2007 to 2010. Of these specimens, stable carbon and nitrogen isotope analyses were also performed on white dorsal muscle tissue from 33 oilfish, 16 escolar, 27 snake mackerel and seven lancetfish. Based on literature length‐at‐maturity values, all escolar, snake mackerel and lancetfish specimens were mature, while 13 of the 33 oilfish were juveniles. Crustaceans, annelids, salps, cephalopods and teleosts were present in the stomachs and were presumed to be prey items. A Kruskal–Wallis test showed the four species to be isotopically segregated in both δ13C and δ15N. Escolar were the most depleted in δ13C, followed by adult oilfish, juvenile oilfish and lancetfish, with snake mackerel the most enriched. The depletion in δ13C of adult oilfish and escolar may have been attributable to high C/N values, which were strongly correlated with length in oilfish, weakly correlated with length in escolar and moderately correlated with length in snake mackerel and lancetfish. The high C/N was likely due to the high lipid concentration of these fishes. Other factors that may have contributed to the depletion in δ13C may include spawning or a change in carbon source within the ecosystem. Large escolar occupied the highest trophic level (δ15N = 10.20), followed by snake mackerel (δ15N = 9.66), adult oilfish (δ15N = 9.32), lancetfish (δ15N = 9.05) and juvenile oilfish (δ15N = 7.83). A marked change in oilfish δ13C and C/N at 30–35 cm fork length coincided with a presumed length‐at‐maturity.

Modelling the Diel Vertical Movement of Swordfish (Xiphias gladius Linnaeus, 1758) Based on Temperature and Depth Recorder Data

Understanding the vertical distribution of large pelagic fish, swordfish in particular, could improve our knowledge on its fisheries strategy, management and resource conservation. However the methods often require expensive tools and resources, which probably most scientists from the development countries couldn’t afford. Thus developing model on the diel vertical movement behavior of swordfish using number of hook between float (HBF) and complete-set temperature and depth recorder (TDR) data could be an alternative. In general context, capture depth distributions are a good indicator of the natural depth distribution of the fish if the entire depth range of the species is targeted by longline gear. The proposed sinusoidal model suggested that swordfish showed a diel pattern in depth distribution, marked by remained in the surface and mixed layer waters at night and dived into deeper waters during the day. Keywords: swordfish, behavior, HBF, TDR, sinusoidal model

Presence of Ruvettus pretiosus (Gempylidae) in the Colombian continental Caribbean

The first record of Ruvettus pretiosus Cocco, 1833 for the Colombian continental Caribbean is presented. The specimen was collected at Los Cocos, department of Magdalena (11°16’33, 84’’ N 73°53’33, 01’’ W), using a demersal longline gear placed at 100 m depth. Biometrics, diagnosis and comments regarding its distribution, ecology and biology are included in the description. This new record expands the distribution of the species in the Caribbean Sea and increases the reported number of gempylids for Colombia to five.