Surface Longline Research Articles

First records from the Mediterranean of a Sooty Shearwater Ardenna grisea caught accidentally by a surface longline

First records from the Mediterranean of a Sooty Shearwater Ardenna grisea caught accidentally by a surface longline

DELTA MODEL APPROACH FOR CPUE STANDARDIZATION OF SWORDFISH (Xiphias gladius Linnaeus, 1978) CAUGHT BY INDONESIAN LONGLINE FLEET IN THE EASTERN INDIAN OCEAN

Relative abundance indices as calculated based on commercial catches are the input data to run stock assessment models to gather useful information for decision making in fishery management. A Generalized Linear Model (GLM) was used to calculate relative abundance indices and effect of longline fishing gear configuration. Data were collected by a scientific observer program from August 2005 to November 2013. Most of the boats monitored were based in the Benoa Port, Bali. Catches are often equal to zero because swordfish is a bycatch for Indonesian longline fleets. Therefore, a hurdle model and a binomial distribution was used to model the proportion of positive catch rates, while a gamma distribution were used to model the positive longline sets. Correlations between the proportion of positive sets and year () and quarter () were weak. However, linear correlation between the proportion of positive sets and the length of branch lines () and number of hooks between floats () were negative and significant. The probability of success is higher for surface longline with small number of hooks and short branch lines. Models with year in interactions as random effects did not converge. Models with year in interactions as fixed effects did converge, but the estimation of standard errors of year coefficients were high. Meaningful estimations were obtained only when using the simplest model, in which year is not in interactions. The low proportional decrease of deviance indicates that most of the variability of catch rates of swordfish caught by Indonesian longline boats are not related to year, quarter, number of hooks between floats and the length of branch lines. Other variables and information, like the daytime while the longlines deployed in the water (day or night), type of bait, size and type of hooks, and if the fishermen use light-sticks to attract the fish, are necessary to better understand the catch rate, and improve the estimations of the relative abundance indices.

Evaluating time-depth recorders as a tool to measure the behaviour of sharks captured on longlines

Quantifying the behavioural response of chondrichthyans to capture in longline fisheries can assist in understanding the physiological changes resulting from capture stress and ultimately aid in developing fishing practices that increase the survival of released bycatch species. Here, we evaluated the use of time-depth recorders (TDR) as a tool to quantify the amount of movement during capture across 42 animals from seven species of shark and one species of ray caught on hooks with TDRs attached in either a demersal or surface longline. Depth changes over time were analysed using three methods to estimate the percentage of time sharks and rays struggled on the line. Methods used were; 1) a Visual Assessment Method (VAM) of the TDR trace conducted by two investigators quantifying movement by summing the duration of movement bouts visually identified by erratic changes of depth; 2) the Gangion Extension Method (GEM) which quantifies movement by summing periods when captured animals altered their depth by >50% of the gangion length; and 3) the Vertical Excursion Method (VEM) which quantifies movement by summing periods when the absolute depth change between successive data points exceeded a threshold determined from the maximum depth change in the TDR data prior to capture of the animal. We found that the VAM was consistent across investigators and produced significantly higher estimates of movement than GEM and VEM. Estimates of movement from GEM and VEM were not significantly different to each other, but unlike GEM, VEM could be applied to TDRs used in both surface and demersal longlines. The amount of movement observed was different between species and such differences were consistent across all methods, indicating that species-specific behavioural responses to capture can be identified. The ability to assess capture behaviour using VEM allows inter-species comparisons, which may be used as a metric for rapid, generalised assessment of species' responses to longline capture where physiological data may be limited or lacking. Such assessments are important in the design of species-specific management for bycaught animals.

Pelagic longline fisheries in southeastern/south Brazil. Who cares about the law?

The fishing industry has been facing problems related to catch yields, predatory competition and economic collapse. Management should be based on substantial scientific studies and the state's ability to implement these. In Brazil, the surface longline fishery has been in existence since the 1950s, and remains of great economic importance. This study analyzes 179 legal instruments (1934–2014), divided into restrictive, administrative and promotional, comparing with catches landed (1996–2011). The results show that there was a complete disrespect for the regulations, wherein fleets continued landing prohibited or size limited species, such as Kajikia albida, Makaira nigricans, Alopias superciliosus, A. vulpinus, Carcharhinus longimanus, Galeorhinus galeus and Xiphias gladius. Furthermore, divergent regulatory provisions have hindered understanding/implementation of regulations by all those involved. Being a country of continental proportions and with different longline fisheries along the coast, conducting scientific studies and the development of normative approaches becomes a huge challenge. In a dynamic activity such as fishing, the constant review of these regulations will allow fisheries management to become more accurate and in accordance with the aspirations of the different interests involved. Despite the surface longline fishery having operated for 60 years in Brazil, the existence of incongruous laws makes the management and control of this activity incompatible with the conservation of species. The lack of regulations governing this fishery creates a "gap", increasing the risk of extinction of species (target and bycatch) and the future collapse of this activity.

Overlap between flesh-footed shearwater Puffinus carneipes foraging areas and commercial fisheries in New Zealand waters

Although the flesh-footed shearwater Puffinus carneipes is a species with large population sizes (tens of thousands of breeding pairs) and widespread sub-tropical distribution across Australasian water masses, it is among the species most threatened by longline fisheries mortality in this region. While bycatch mitigation measures have been very successful in reducing mortality in some species, bycatch of flesh-footed shearwaters is still high, with captures estimated to exceed the sustainable take of 514 birds yr-1 by nearly 200 birds for New Zealand fisheries alone. Management agencies aiming to reduce the impact of fisheries mortality on the populations need to understand which marine areas are being used by flesh-footed shearwaters to better target fishery monitoring and mitigation efforts. Foraging studies of seabirds tell us about their use of resources, i.e. the way species segregate the available habitat and help to identify threats that may affect population viability. Breeding shearwaters were tracked from 2 New Zealand colonies using GPS loggers. Individuals foraged over shelf and deep oceanic waters up to 1200 km from their nesting sites during incubation but were mainly within 370 km during early chick rearing. The intensity of potential interactions increased for trawl and surface longline fishing between the January and February study periods but remained at a similar level for bottom longline fishing. Following the field data collection, changes to fishery monitoring were implemented in the areas where shearwaters foraged.

Analysis of swordfish surface longline fishery in Andalusia, Spain

Analysis of swordfish surface longline fishery in Andalusia, Spain

Age, growth, biological and ecological aspects of Remora osteochir (Echeneidae) in the Mediterranean Sea

This paper provides for the first time data on age and growth ofRemora osteochir, also describing its sagittal otolith together with other biological and ecological aspects. Overall, 236 individuals of marlin sucker were collected in the southern-central Mediterranean Sea, from 2008 to 2009. All samples were hosted by the Mediterranean spearfish,Tetrapturus belone, caught by surface longline and harpoon. Analysis of gonads identified a reproductive peak during June and July. The estimated growth parameters according to the von Bertalanffy equation were:L∞= 27.37 cm TL,k= 0.248 year−1,t0= −1.36 year. The length-weight relationship, computed by using eviscerate weight, highlighted an isometric growth for both sexes, as supported by the other results: similar sizes, growth curves and disc length-total length relationship.

Lightsticks content toxicity: Effects of the water soluble fraction on the oyster embryonic development

Lightsticks are artifacts used as attractors in a type of commercial fishery, known as surface longline gear. Despite the excessive use, the contamination risks of these devices have not yet been properly investigated. This research aimed to fill up this gap by determining the chemical composition and the toxicity of lightsticks recently activated, compared to those one year after activation and to the ones collected on the beaches. The analyzes were carried out by Gas Chromatography coupled with Mass Spectrometry (GC–MS). Additionally, the variations in composition and the toxicity of their sea Water Soluble Fractions (WSF) were evaluated based on the WSF-effects of Crassostrea rhizophorae embryonic development. The GC–MS analysis made possible the identification of nineteen substances in the water soluble fraction of the lightsticks, such as dibutyl phthalate (DBP) and dimethyl phthalate (DMP). The value of the WSF-effective concentration (EC50) was in an average of 0.35%. After one year of the lightsticks activation, the toxicity was even higher (0.65%). Furthermore, other substances, also present in the lightsticks-WSF caused persistent toxicity even more dangerous to the environment than DBP and DMP. This essay discusses their toxicity effects and possible environment damages.

Age, Growth and Reproduction of Coryphaena hippurus (Linnaeus, 1758) in Maltese Waters, Central Mediterranean

Age, growth and reproduction of the dolphinfish Coryphaena hippurus Linnaeus, 1758 collected from the Central Mediterranean in the period 2004-2010 by the traditional Maltese fish aggregating devices (FAD) and surface longline fisheries were studied. The a and b parameters of the length-weight relationship for fish 11-142 cm fork length (FL) (n = 4042) were determined as a = 0.018 and 0.022 with b = 2.85 and 2.79, for males and females respectively. The counting of annual increments from dorsal spines of >65 cm FL dolphinfish at X25 magnification (n = 47) permitting an age reading resolution in years , and the counting of daily increments from sagittal otoliths of <65 cm FL dolphinfish at X400 magnification (n = 583) permitting an age reading resolution in days, were estimated; the von Bertalanffy growth model applied to these fish gave the following parameters: L∞ = 107.8 cm FL and 120.2 cm FL, and K = 1.9 yr-1 and 1.56 yr-1, for males and females respectively. The maximum age observed was 2 years. Size at 50% maturity for fish 10-131 cm FL (n = 1376) was 58.9 cm FL and 62.5 cm FL for males and females, respectively. The sex ratio for the fish sampled from the FAD fishery (10.5-131 cm FL) was 1:1.54 (M:F) and for dolphinfish sampled from the surface longline fishery (91-130 cm FL) was 1:0.76 (M:F). Back-calculated hatch dates from age-0 dolphinfish (n = 518) suggested that spawning occurs from June to September with the highest levels in June. This study is the first to use dorsal spines to determine the age of adult dolphinfish.

Seasonal effects of the seeding on the growth of Chilean mussel ( Mytilus edulis platensis, d'Orbigny 1846) cultivated in central Chile

Abstract This study presents a background on growing Mytilus edulis platensis , which were seeded on both summer and winter seasons. Surface longline systems were installed at a lower latitude zone than mussel aquaculture industries along Llico bay, VIII region (Biobio) of Chile. Mussel seeds were transferred from X region (Los Lagos) the traditional region for culture mussels. The first seeding was carried out in February (summer) and the second in July 2009 (winter). In the culture period, shell length, total weight and weight of fresh meat were measured. During the study, seeded mollusks in summer and winter seasons grew 3.03 and 4.37 mm month − 1 , on average, respectively. It was observed that for the same asymptotic length ( L ∞ = 79.1 mm), the value of the metabolic constant was higher in winter ( k Li = 0.1995) than in summer ( k Lv = 0.1492), and for the same asymptotic weight ( W ∞ = 40.79 g), the k value was higher in winter than in summer ( k wi = 0.1643 and k wv = 0.1392, respectively). Cultivation time and seeding season have a significant effect on growth in both length and total weight ( p p > 0.05). It can be concluded that seeding in winter has a positive effect on growth, decreasing the cultivation time for a harvest size more than the commercial size in 3 months (shell length ≥ 50 mm).

SHARK LONGLINE FISHERY IN TANJUNGLUAR-EAST LOMBOK

Studies on artisanal shark fisheries in Tanjungluar - East Lombok were conducted during the year 2001-2011 (except in 2003 and 2007). A sampling method called “rapid market survey” method was employed to collect catch data from surface and bottom longlines fishing, rapidly. Biological data and fisheries data were collected during survey. Catch data for shark were also obtained from daily records filled by TPI officers in Tanjungluar between 2009 and 2010. The results showed that shark<br />longline fishing was conducted every month. The trend of shark catches relates to the number of fishing vessels, fishing ground, and weather conditions at sea. The period between July and September is a transitional season from East to West seasons. During this season, the wind strength is weakened and a good fishing season for the fishers. The lowest catch occurs in January (1.06 tonnes) and the highest catch in September with the total catch of 24.6 tonnes. Sharks caught by surface longline were dominated by Silky shark, Carcharhinus falciformis (40-90%) with the size range of 100-125 cm. The catch of bottom longline was mostly consisting of fish in mature condition that dominated by Grey reef shark (<em>Carcharhinus amblyrhynchos</em>), Common black tip shark (<em>C. limbatus</em>), Spot tail shark (<em>C. sorrah</em>), and Scalloped hammerhead shark (<em>Sphyrna lewini</em>), with the size range of 125-200 cm, 170- 250 cm, 100-150 cm, and 170-300 cm, respectively. Surface longline fishing occurs in the offshore waters in depth more than 200 m to 3000 m, whereas bottom longline fishing is operated at a depth of 50-100 m around islands.

Circle hooks: Developing better fishing practices in the artisanal longline fisheries of the Eastern Pacific Ocean

Since 2004, governments and non-governmental organizations, together with the fishing communities from nine countries, from Mexico to Peru, have implemented joint efforts to reduce incidental mortality of sea turtles in artisanal longline fisheries of the Eastern Pacific Ocean (EPO). These countries are involved in a Regional Sea Turtle Bycatch Program to achieve this goal. Circle hooks have been proposed as a way to mitigate incidental mortality of sea turtles. Thus, we analyze the performance of circle hooks in relation to J-style and tuna hooks on the hooking rates of target and non-target species in the artisanal surface longline fisheries of three of the participating countries with the largest sample sizes (Ecuador, Panama and Costa Rica). These fisheries target mahi-mahi, Coryphaena hippurus, or a combination of tunas, billfishes and sharks (TBS), and use different techniques and gear configurations to catch their targets. For the TBS fishery we presented the results of comparisons between tuna hooks and 16/0 circle hooks from Ecuador, Panama and Costa Rica, and between tuna hooks and 18/0 circle hooks in Costa Rica. For the mahi-mahi fishery, we analyzed the performance of 14/0 and 15/0 circle hooks in Ecuadorian vessels and 16/0 circle hooks in Costa Rican vessels vs. the traditional J-style hooks. A total of 730,362 hooks were observed in 3126 sets. Hooking rates for target and non-target species were not consistent for all fisheries and countries analyzed. However, circle hooks reduced sea turtle hooking rates in most of the comparisons.

By-catch frequency and size differentiation in loggerhead turtles as a function of surface longline gear type in the western Mediterranean Sea

Fisheries by-catch is considered to be a major threat to loggerhead turtles in the Mediterranean Sea. Technical differences in both gear configurations (e.g. hook and bait type) and fisheries operations carried out by the Spanish Mediterranean surface longline fleet could have an effect on by-catch rates and size selectivity. The aim of the present study was to test the differences in by-catch per unit effort and body size of loggerhead sea turtles caught using different gear types in the Mediterranean surface longline fishery. Our results suggest that differences in the gear type used have an effect on catch rates and size selectivity. Thus, surface longliners targeting albacore (LLALB) using smaller hooks tend to capture smaller loggerheads but have the highest by-catch per unit of effort (BPUE), whereas other longlines, such as surface longliners targeting bluefin tuna (LLJAP) and traditional surface longliners targeting swordfish (LLHB), using larger hooks tend to select the larger animals; moreover, LLHB had the lowest BPUE. Disproportionate rates of fisheries-induced mortality on certain size/age-classes can differentially affect sea turtle populations, as each sea turtle age-class contributes differently to current and future reproduction. Thus, fisheries management should not only be focusing on preserving the large juvenile and mature turtles, but also on reducing the total by-catch. Thus, we recommend encouraging the use of LLHB versus other surface gears. We suggest that it is very important to take into account the gear type (and its particular catch rates) when making inferences about the impact of longline fisheries on sea turtle populations.

From surface to mid-water: Is the swordfish longline fishery “hitting rock bottom”? A case study in southern Italy

Fleet expansion, increased gear efficiency, increased effort and the constant improvement in fishing methods have greatly contributed to the current overexploitation of many target stocks. It is therefore essential to identify and monitor the changes in fishing practices as well as the technological creep to determine their implications for the conservation of target and non-target species. The present study documents the recent technical and operational changes in a longline fishery targeting swordfish (Xiphias gladius) operating in southern Italy (Ionian Calabria). Data collected during the swordfish fishing seasons of 2007, 2010 and 2011 showed a significant change in fishing practices over the survey years, as the longline fishery switched from surface (10–100m) to mid-water (100–500m) depth and from 11h to 25–30h soak time. These modifications in fishing operations, which result in an increase and redistribution of the effort, were motivated by a drastic decrease in the swordfish catches made with the traditional surface longline. They have modified the fleet structure, catch species composition and size of the target species. Although these operational changes resulted in an increase in the swordfish size and a decrease in the sea turtle bycatch, their implications for less known and potentially more vulnerable commercial and bycatch species are unclear. Moreover, the shift of fishing effort into deeper water is a well-documented evolution of many fisheries worldwide in response to the decline in shallow coastal water resources. The change in fishing practice of the pelagic longline fishery reported in the present study could be considered an additional alarm bell of the current state of overexploitation of the Mediterranean swordfish.

Incidental captures of sea turtles in the driftnet and longline fisheries in northwestern Morocco

The Moroccan port of Tangier along the Strait of Gibraltar holds a very strategic position biologically, and fisheries and sea turtle populations inevitably interact in this region. The objective of this study was to assess the impact of fishing gear commonly used in Tangier – the driftnet and surface and bottom longlines – on sea turtles in Moroccan waters. Over the 4 years of the study (2003–2004 and 2006–2007), a total of 73 turtles were caught in the driftnets of the 7 vessels studied during 866 fishing days, and 13 turtles in the 4 artisanal longlines vessels evaluated during 593 fishing days. The average estimated catch by the entire fleet using driftnets in the region of Tangier during the years of study is 719 (SD=543) captures of loggerheads/year and 101 (SD=57) captures of leatherbacks/year. In the two longline fleets, the average estimated turtle capture in a year was 51 turtles (range=20–97 turtles; SD=31) by surface longline and 91 turtles (range=0–260 turtles; SD=62) by bottom longline. Drift gillnets appear to have the highest interaction with sea turtles, but new legislation requires that driftnets must be phased out by 2012. However, increasing vigilance will be needed as the port of Tangier plans to expand and increase its capacity and as driftnets are replaced by commercial longlines and other gear types. Given that Moroccan fisheries are impacting sea turtles originating from several nesting populations in the western and eastern Atlantic and the Mediterranean, evaluating and mitigating mortality of sea turtles in Morocco and creating a greater awareness for their protection are crucial to the survival and recovery of several nesting populations.

Fish resources management in Brazil and overview of artisanal fisheries in Macaé, RJ

The aim of this review is to highlight the sociocultural and environmental importance of artisanal fisheries for the city of Macaé, Rio de Janeiro, Brazil, providing information about the main artisanal fisheries methods applied by the fishers, a brief history of public policy for fishing in Brazil, and an overview of the economy working relations and fish marketing in that city. Once the definitions of artisanal and industrial fishing are modified according to the State or region, we are consider artisanal fishing, for the purpose of this work, as that practiced by professional fisherman directly, independently, or as family economy, with production means of their own, or through partnership contract, landed, allowing the use of small ships. Five main artisanal fishing methods were detected in Macaé: (i) the line method, (ii) the method of surface longline; (iii) the driftnet method; (iv) the drag; and (v) the method of network seines, or pair. In this analysis, we focused on four major public policy processes which led to setting up a model of fishery management, in which crisis is evident, with an overcoming not yet fully delineated. Since the fishing activity is important for the region, the development of studies able to define the supply chain structuring programs, expansion of investments, creation of a framework for its own staff and, especially aimed at management concepts that can coordinate all activity from production, through processing to marketing, are significant steps to strengthen the fisheries policy in the city of Macaé.

Diving behavior of the giant devil ray in the Mediterranean Sea

The giant devil ray Mobula mobular is the only mobulid species regularly present in the Mediterranean Sea. The spatial ecology and biology of this species are poorly known, and given its high bycatch mortality, low reproductive capacity, and limited range, it is listed as Endangered (A4d) on the IUCN Red List. Most of the information concerning this species has been obtained through bycatch data and opportunistic sightings. To inform conservation and management actions, it is nec- essary to conduct research on the behavior of giant devil rays. This study is the first attempt to sys- tematically describe the diving behavior of this species. Three specimens were tagged with popup satellite tags in the Messina Strait (central Mediterranean Sea) during summer 2007. Two tags were programmed to detach after 120 d and 1 after 60 d. The data revealed that these fish dove to depths between 600 and 700 m. However, they spent most of their time (81.5%) between the surface and 50 m, in waters with temperatures between 20 and 29°C. The preference for shallow depth and warm surface waters exposes this species to threats such as accidental captures in driftnets and surface longlines.

On the diet and reproduction of the oilfishRuvettus pretiosus(Perciformes: Gempylidae) in the eastern Mediterranean

The oilfish,Ruvettus pretiosus, is an incidental by-catch of the drifting surface longlines targeting swordfish and Thunnidae in the Mediterranean and elsewhere. Despite its global distribution and frequent occurrence in the catch of many fishing gears, little is known about its biology. In this study we examined the dietary preferences and reproductive biology of this species from specimens caught in the eastern Mediterranean. The most numerous and frequently occurring prey items were benthopelagic fish, followed by cephalopods. The sex-ratio was highly skewed in favour of females (1:8.4), while histological examination of the collected ovaries displayed six developmental stages (perinucleolar, early and late lipid stage; early, middle and late vitellogenesis). Oocyte diameter ranged from 23–69 μm at the perinucleolar stage to 224–366 μm at the late vitellogenesis stage. Spawning is expected to occur during mid and late summer; however there were no individuals available from this period. The findings are discussed in relation to the ecology of the species.

ESPÉCIES DE ELASMOBRÂNQUIOS DESEMBARCADAS NO PORTO DE ITAJAÍ, SUL DO BRASIL

Fishing activity in the Itajai harbor (SC) has concentrated a large fishing fleet, operating with many different methods of capture. This paper presents a checklist of the species of elasmobranchs landed in Itajai, and analyses the respective landing frequencies in the fishing methods. Elasmobranchs were observed in catches of purse seine, single trawl, double rig trawl, pair trawl, surface longline, bottom longline, surface gillnet, bottom gillnet and traps. In total, 85 species were found (54 sharks and 31 skates and rays) and of them, 22 shark species and 6 skates were very abundant in at least one fishing art.

Validating an ecological model with fisheries management applications: the relationship between loggerhead by-catch and distance to the coast

On the one hand, a recent study on sea turtle by-catch during surface longline fishing targeting swordfish in the western Mediterranean Sea showed that sea turtle by-catch is independent of fishing effort and other technological factors. When the distance to the coast increases, there is a higher probability of catching a loggerhead turtle. The authors proposed to avoid fisheries further than 35 nautical miles (approximately 65 km) from the coast. However, the proposed 35 nautical miles limit could be useful where the continental shelf is narrow, as in the Balearic Sea, and useless where it widens. On the other hand, ecological model validation is considered essential for management application. The objective of the present paper is to validate the new fisheries loggerhead by-catch model in different areas outside the Balearic Sea with wider continental shelves, aimed at maintaining sustainable fishing activity compatible with the conservation of the loggerhead populations. Our present results validate the previous model, and stress the importance of the eco-geographical variable distance to the coast in understanding the loggerhead by-catch (or incidental capture) per unit effort for the longline fisheries targeting swordfish.