Striped Marlin Research Articles

The effects of circle hooks on bycatch and target catches in Australia's pelagic longline fishery

We assess the performance of circle hooks, which are promoted as a measure for improving the survival of marine turtles following interactions with pelagic longlines. We conducted experiments off eastern Australia on commercial fishing vessels that alternated circle hooks (mostly size 14/0) and Japanese tuna hooks along their longlines. Most animals were hooked in the lip or jaw, regardless of hook type. There was no difference in the mean size of animals caught on the two types of hook, except for striped marlin ( Tetrapturus audax), which tended to be larger on tuna hooks. Most species had an equal or lower probability of being alive on circle hooks than tuna hooks. Catch rates on circle hooks exceeded those on tuna hooks for most species. These included several target species, such as albacore tuna ( Thunnus alalunga), yellowfin tuna ( Thunnus albacares) and striped marlin, and bycatch, including several shark species. The differences in catch rates were large enough to increase total catches and financial returns. The financial benefits of increased catches outweighed the costs of converting to circle hooks. The results indicate that the adoption of small circle hooks by longliners will not be detrimental to financial returns.

Stable isotopic evidence for trophic groupings and bio-regionalization of predators and their prey in oceanic waters off eastern Australia

Muscle tissue was collected for stable isotope analysis (SIA) from the main fish predators and their fish and cephalopod prey from oceanic waters off eastern Australia between 2004 and 2006. SIA of δ15N and δ13C revealed that the species examined could be divided into three main trophic groups. A “top predator” group consisted mainly of large billfish (Xiphias gladius and Tetrapturus audax), yellowfin (Thunnus albacares), bigeye (T. obesus) and southern bluefin (T. maccoyii) tunas and sharks; with mako (Isurus oxyrinchus) the highest. Below this tier was a second group composed of mid-trophic level fishes including albacore tuna (Thunnus alalunga), lancet fish (Alepisaurus ferox), mahi mahi (Coryphaena hippuris) and ommastrephid squid. Underlying both groups was a grouping of small fishes including myctophids, small scombrids and nomeids as well as surface fishes including macrorhamphosids. These groupings were based largely on mean animal size which showed a positive linear relation to δ15N (r2 = 0.58). Some species showed significant ontogenetic variation in either δ15N (swordfish, lancet fish, yellowfin and albacore tuna) or δ13C (mako shark). We also noted a consistent latitudinal change in δ15N and δ13C at ~28°S for the top predator species, particularly albacore and yellowfin tuna. The differences were consistent with a change from oligotrophic Coral Sea to nutrient rich Tasman Sea waters. These differences suggest that predatory fishes may have extended residence time in distinct regions off eastern Australia.

Species catch composition, length structure and reproductive indices of swordfish (Xiphias gladius) at Easter Island zone

The species composition, size distribution, and gonadal index (GI) of swordfish (Xiphias gla- dius) are reported from catches obtained by longliners in the zone of Easter Island in the southeastern Pacific. Five cruises were made during the summer season between 2001 and 2006 completing a total of 150 fishing sets. A total of 3,781 fish belonging to 24 species were registered, of which 17 were commercial and 6 were bycatch. Of the total, 44.1% were swordfish, 28.3% sharks, 12.1% marlins, 8.4% tunas and 7.1% other teleosts. Amongst the sharks the most important species was the blue shark (Prionace glauca, 16.5%) fol- lowed by the brown shark (Carcharhinus spp., 6.9%). Amongst the tunas and istiophorids, striped marlin (Tetrapturus audax, 8.0%) and yellowfin tuna (Thunnus albacares, 4.9%) were also important (≥ 4% in num- ber). The number of units by species, the nominal yield in number and weight and the gutted average weight are reported in addition to size statistics. The population structure of swordfish was dominated by males and differences in the average length between sexes were not found. Individuals with high values of GI were ob- served during every survey, mainly during December-February which suggests a reproductive area for this species. The blue shark showed a predominance of males, and differences in the average length between sexes were observed, possibly due to a spatial and temporal segregation.

Near real time satellite tracking of striped marlin (Kajikia audax) movements in the Pacific Ocean

High-resolution satellite locations were obtained from striped marlin using Argos transmitters attached to the upper lobe of the caudal Wn. Twenty-six striped marlin were tagged oV New Zealand (2005-2007) and tracked as far as the central PaciWc Ocean. Caudal Wn mounted Argos tags generated 1,524 locations during a total of 659 tracking days (mean 25 (§21.24) days per Wsh and 2.3 (§2.30) locations per day). 38% of locations have an estimated accuracy of §1 km or better. Displacement rates from high quality locations ranged from 2.9 to 170.8 km in a 24 h period, with a mode at 20-30 km and a mean of 45 km/day. The caudal Wn attachment methodology and antenna conWguration was adjusted each season to improve transmission life and data quality, with the best results obtained in the last year of deployments (2007). The longest track duration was 102 days, with a total displace- ment of 4,959 km and a total track distance from all loca- tions received of 6,850 km. Tag shedding and antenna failure appear to have limited the duration of tracks from SPOT tags. The high temporal and spatial resolution data revealed behaviours not previously observed in striped marlin, including associations to subsurface bathymetric features. High resolution location data such as these are useful inputs for statistical models used to investigate habitat selection and switching between diVerent behavioural modes. The geolocations calculated using ukfsst estimates from PAT tag data had RMS errors of 1.01° latitude and 0.59° longi- tude when compared with SPOT tag Argos locations.

Effect of bait species and color on sea turtle bycatch and fish catch in a pelagic longline fishery

The effects of bait species (mackerel and squid) and color (blue-dyed and non-dyed) on the loggerhead turtle Caretta caretta bycatch in a pelagic longline fishery in the western North Pacific were assessed in shallow-set longline fishing experiments. The loggerhead turtle catches were analyzed using a generalized linear model (GLM) with a Poisson distribution. The potential factors (bait species, bait color, other species catch, and sea surface temperature) affecting loggerhead turtle catch were incorporated as explanatory variables. The model analyses indicated that bait species affected loggerhead turtle catch, while bait color did not. The model predicted that catch rates of loggerhead turtles were 75% less on mackerel bait to squid bait. This study demonstrated that fish bait choice was very effective in reducing loggerhead turtle bycatch in pelagic longline fisheries, but that the use of blue-dyed bait was not. Similar model analyses were also performed on target and by-product fish species, such as swordfish Xiphias gladius, striped marlin Tetrapturus audax, bigeye tuna Thunnus obesus, blue shark Prionace glauca, and shortfin mako shark Isurus oxyrinchus, and other non-target species. The remarkable differences between bait species and color that were found for loggerhead turtles were not found for these species catches.

Effects of eliminating shallow hooks from tuna longline sets on target and non-target species in the Hawaii-based pelagic tuna fishery

A longline experiment consisting of 45 paired sets (90 sets total) was carried out to evaluate a technique which maintains target catch rates while reducing non-target catch rates. Control sets were compared to experimental sets which eliminates the shallowest hooks (∼less than 100 m depth). Researchers hypothesized that by eliminating shallow hooks, target catch of deeper dwelling species such as bigeye tuna ( Thunnus obesus) would be maximized while incidental catch of many other non-target, but marketable epi-pelagic species (e.g. billfish), bycatch (discards) of other fishes and elasmobranchs, and protected sea turtles and marine mammals would be simultaneously reduced. To control for differences in fishing power, gear, and deployment techniques; a single vessel was contracted to perform all 90 paired longline sets (45 experimental sets using no-shallow-hooks and 45 control sets using standard methods). Control sets consisted of longlines that were suspended by floats on typical 30 m long floatlines in catenary-type shapes that fished a range of depths, determined by temperature–depth recorders (TDRs) to be 44–211 m (27.5–11.2 °C). By contrast, elimination of shallow hooks in the upper 100 m of the water column (hereinafter referred to as experimental sets) was achieved by suspending the fishing portion of the mainline on 75-m long, 3 kg weighted vertical sections of mainline suspended by floats on 30 m floatlines. As determined by TDRs, this arrangement ensured that all hooks fished at depths >100 m (103–248 m; 24.8–11.3 °C). Thirty percent of hooks in control sets fished at depths less than 100 m while all hooks on experimental gear fished greater than 100 m. Because many factors influence catchability, longline sets are by nature multivariate, and statistical comparisons were made between the two set types using canonical discriminant analysis (CDA). Except for the depth of shallow hooks, operational characteristics between experimental and control sets were the same. The catch rates of bigeye tuna were similar on the two sets types but the catch rate of sickle pomfret ( Taractichthys steindachneri) was significantly higher ( p = 0.011) in the experimental sets as compared to control sets. However, statistically fewer wahoo ( Acanthocybium solandri, p = 0.019), dolphinfish ( Coryphaena hippurus, p = 0.008), blue marlin ( Makaira nigricans, p = 0.001), striped marlin ( Kajikia audax, p = 0.018) and shortbill spearfish ( Tetrapturus angustirostris, p = 0.006) were captured on the experimental sets; thus longline interactions and impacts on these species were reduced with the experimental gear. The reason for the differences in catch rates between gear types is likely due to the vertical habitat preferences of the species involved; interactions with epi-pelagic species with shallow distributions in the uniform mixed layer were reduced by deploying hooks greater than 100 m. By logical extension, the experimental gear will also likely reduce interactions with sea turtles. Except for additional lead weights, floats, and floatlines, only slight modification of existing longline fishing gear and methods were required to deploy the experimental gear. The main drawback of this method was the increase in time to both deploy (≈0.5 h) and retrieve (≈2 h) the gear. Knowledge of species vertical distribution patterns can play an important role in modifying fishing gear to reduce bycatch and can also assist managers in regulating fishing practices with a higher degree of likelihood of predicting catch rates and species captured in different gear types.

Population structure of striped marlin (Kajikia audax) in the Pacific Ocean based on analysis of microsatellite and mitochondrial DNA

Genetic variation was surveyed at five microsatellite loci and the mitochondrial control region (819 bp) to test for the presence of genetic stock structure in striped marlin ( Kajikia audax ) collections taken from seven locations throughout the Pacific Ocean. Temporal replicates separated by 9 years were taken off Japan, and three temporal samples spanning 11 years were collected off the coast of eastern Australia. Analyses of multilocus microsatellite genotypes and mitochondrial control region sequences showed no significant heterogeneity among collections taken from the same location in different years; however, significant spatial genetic heterogeneity was observed across all samples for microsatellite markers (FST= 0.013, P < 0.001). Mitochondrial control region sequences were not different across all samples (ΦST= –0.01, P = 0.642). Analyses of molecular variance (AMOVA) revealed significant genetic differentiation between geographic regions for both microsatellite and mitochondrial markers. These results suggest the presence of genetically discrete populations within the Pacific Ocean and are supported by both the results of tagging studies, which show limited dispersal, and the presence of geographically separated spawning grounds.

The relative importance of lunar phase and environmental conditions on striped marlin ( Tetrapturus audax) catches in sport fishing

We used generalized additive mixed models to analyze data on striped marlin ( Tetrapturus audax) catches in Baja California sport fisheries (1987–1989) to investigate the relative importance of lunar phase, sea surface temperature (SST), El Niño/Southern Oscillation (ENSO) index, and vessel effects on catch per unit effort (CPUE). The results indicate that the moon phase has no or little (<1% of variance explained) influence on CPUE. In contrast, both SST (10%) and ENSO (6%) influenced CPUE positively. While most of the variation in CPUE remains unexplained (53%), the vessel identity explained small (ca. 1.5%) but significant amount of variance in CPUE. Hence, sport fishermen wishing to maximise their striped marlin catches would best plan their trips on the basis of weather conditions and boat/crew identities, rather than on the basis of lunar phase.

Striped marlin (Tetrapturus audax) movements and habitat utilization during a summer and autumn in the Southwest Pacific Ocean

AbstractSix striped marlin (Tetrapturus audax) were caught on hook and line from recreational fishing boats near northern New Zealand (34°S, 174°E) and tagged and released with pop‐off satellite archival tags. For periods ranging from 22 to 60 days over the geographical range 168°E–170°W and 13–34°S, five tags collected a total of 202 days (range of 21–60 days) of data. These data permit the investigation of striped marlin geographical and vertical movements and water temperatures occupied from February to June 2003. One hundred and one days of geoposition data showed a preliminary view of their movements in and around New Zealand waters. Transmitted temperature and depth data indicated striped marlin spent 80% (±2%) of their time in the mixed layer including 72% (±2%) of their time in the top 5 m. Temperature data indicated 75% (±10%) of the striped marlin’s time was spent in water temperatures between 20.1 and 24.0°C. Tagged striped marlin moved faster during periods of directed movement away from New Zealand versus periods of passive movements when the fish were proximal to New Zealand or not moving in any specific direction. These data support some existing hypotheses about striped marlin physiological ecology and allow preliminary suggestions about how striped marlin bycatch might be reduced.

Circle Hooks for Pacific Longliners: Not a Panacea for Marlin and Shark Bycatch, but Part of the Solution

AbstractBlue marlin Makaira nigricans, striped marlin Tetrapturus audax, and pelagic sharks (e.g., blue shark Prionace glauca) are commonly caught as bycatch by longline fisheries in the central North Pacific Ocean. Recently, concern has increased about depletion of these species. Modifications in longline gear may offer one solution. Here, we test the use of circle hooks, rather than the conventional tuna‐style hooks, on longlines using an ecosystem model of the central North Pacific Ocean. The simulations considered span a range of reasonable circle hook catchability and survival rates for released fish. The results suggest that if circle hooks have higher catchability than the currently used tuna‐style hooks, switching to circle hooks depletes marlin biomass by 25–40% and shark biomass by 15–35% over 30 years. However, these depletions do not occur if circle hook catchability is equal to or lower than that of tuna‐style hooks. When the effects of catch‐and‐release requirements for marlins and sharks were also considered, we found that regardless of assumptions about circle hook catchability and survival rates, a combined policy of using circle hooks and releasing sharks and marlins leads to net increases in marlin and shark abundance. The simulations show a trade‐off between the abundance of marlins and sharks and their prey items, yellowfin tuna Thunnus albacares and small blue sharks. There is also evidence of trophic trade‐offs between yellowfin tuna and small blue sharks and their prey, small scombrids (Auxis spp.) and mahi mahi Coryphaena hippurus. The results illustrate the importance of understanding catchability and survival rates for circle hooks compared with those for tuna‐style hooks and encourage further research in this area.

Rapid PCR-RFLP Method for the Identification of 5 Billfish Species

ABSTRACT: A rapid and reliable polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was developed to identify billfish species Xiphias gladius (swordfish), Makaira nigricans (blue marlin), Makaira indica (black marlin), Istiophorus platypterus (sailfish), and Tetrapturus audax (striped marlin). After DNA extraction and amplifying, the 348-bp PCR products from gene encoding of cytochrome b were subjected to restriction enzyme analysis. No single enzyme tested was able to distinguish the 5 species at the same time, but the combination of results obtained from the digests of Bsa JI and Cac 81 could be used to differentiate the 5 billfish species. This sensitive, rapid, and valid method can be used to detect fraudulent substitutes.

Relationships between bait collection, bait type and catch: A comparison of the NSW trailer-boat and gamefish-tournament fisheries

Information from separate angler surveys was analysed to examine the relationships between bait use and catch composition for both the New South Wales (NSW) trailer-boat fishery and the NSW gamefish-tournament fishery. Anglers in both fisheries were categorised as either “baitfish harvesters”, i.e. anglers who collected baitfish as part of their fishing trip, or “baitfish non-harvesters”, i.e. anglers that did not collect baitfish as part of their fishing trip. Multivariate analysis (multidimensional scaling analysis (MDS) and Similarity Percentages analysis (SIMPER) analysis) was carried out to determine the relationship between bait use, bait type (live bait, dead bait and lure) and catch of target species. Predominant species harvested for use as live bait in both fisheries were blue mackerel ( Scomber australasicus) and yellowtail scad ( Trachurus novaezelandiae). Significant differences were found between “baitfish harvesters” and “baitfish non-harvesters” and catch within the trailer-boat fishery. However, there was no corresponding trend for competition gamefish anglers. Ordination of capture information obtained from gamefish tournaments, categorised by bait type (live baitfish, dead bait and lure), identified associations between the use of live baits and striped marlin ( Tetrapturus audax) and dead baits and short-finned mako sharks ( Isurus oxyrichus).

Using the PCR–RFLP method to identify the species of different processed products of billfish meats

A polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) method had been developed for the detection of five billfish species Xiphias gladius, Makaira nigricans, M. indica, Istiophorus platypterus and Tetrapturus audax in raw, frozen and heat-treated meats. The primers L-CYTBF and H-CYTBF were designed in the mitochondrial cytochrome b ( cytb) gene and the molecular weight of amplified fragment was 348 bp and amplified the fragment from processed billfish meats. The results obtained from the BsaJI, Cac8I and HpaII enzymes digestion could be used to distinguish the five billfish species in frozen and heat-treated meats. Using the PCR–RFLP method, species of 10 commercial samples including raw fish fillets, frozen fish meats and fried fish meats could be identified. It was determined that two commercial samples of billfish products were not made from billfish. The method is sensitive, rapid and valid to detect fraudulent billfish products substituted from cheaper fish.

Two Anisakid Nematodes from Marine Fishes off New Caledonia, Including Raphidascaris (Ichthyascaris) nemipteri n. sp. from Nemipterus furcosus

One new and one known species of the ascaridoid family Anisakidae are reported from marine fishes off the southwestern coast of New Caledonia: Raphidascaris (Ichthyascaris) nemipteri n. sp. from the intestine of the forked-tailed threadfin bream Nemipterus furcosus (Nemipteridae, Perciformes) and Hysterothylacium cenaticum (Bruce and Cannon, 1989) from the intestine of the striped marlin Tetrapturus audax (Istiophoridae, Perciformes). R. nemipteri is characterised mainly by the shape (wider than long) of the lips, the length of the spicules (225-399 microm, which represent 2.7-4.2% of the body length), the number (22-33) of caudal pre-anal papillae, the position of the vulva (at 16-20% of the body length), and the presence of cuticular spines on the tip of the female tail. Specimens of H. cenaticum from New Caledonia generally exhibited smaller body measurements than those originally described from Australian waters; the deirids and eggs are described for the first time. Maricostula Bruce and Cannon, 1989 is considered a junior synonym of Hysterothylacium, to which three species are transferred as H. cenaticum (Bruce and Cannon, 1989) n. comb., H. makairi (Bruce and Cannon, 1989) n. comb. and H. tetrapteri (Bruce and Cannon, 1989) n. comb.

Size trends and population characteristics of striped marlin, Tetrapturus audax caught in the New Zealand recreational fishery

Size trends and population characteristics of striped marlin, Tetrapturus audax, caught in the New Zealand recreational fishery were evaluated using club records from the Bay of Islands Sword‐fish Club (BOISC) from 1925 to 2003 (n = 15 114) and biological samples from northern New Zealand collected from 1985 to 1994 (n = 684). Average weight (kg) ± SE of striped marlin declined 6–9 kg every 20 years between 1925 (124.2 ± 1.0 kg) and 2003 (100.1 kg ± 0.4). Weight (H14843 = 444.58, P < 0.001) and condition (H443 = 37.54, P < 0.001) increased significantly throughout the recreational fishing season (December‐May). No differences were observed in the lower jaw‐fork length (LJFL)‐weight (W) relationship between sexes or years but average weight of females (106.2 ±1.1 kg) was significantly greater than males (90.2 ±1.2 kg) from 1985 to 1994 (F684 = 88.37, P < 0.001). Negative allometric growth (W = 2E ‐08 LJFL2.88) was recorded for all striped marlin. Individual growth was modelled by fitting backcalculated LJFL to eight age classes derived from dorsal spine measurements (n = 94) using the von Bertalanffy growth equation (r2 = 0.96). The parameters estimated in the von Bertalanffy growth equation were asymptotic length (L ) = 3010 mm, annual growth rate (K) = 0.22, age (yr) at hypothetical length 0 (t0) = ‐0.04.

Analysis of logbook accuracy for blue marlin (Makaira nigricans) in the Hawaii-based longline fishery with a generalized additive model and commercial sales data

Abstract Blue marlin, Makaira nigricans , catch (number per set) in the Hawaii-based longline fishery from March 1994 through June 2002 was analyzed by integrated use of observer reports, commercial logbooks, and auction sales records. The objective was to provide a corrected catch history for this species in this fishery during this period. The study was conducted because official statistics compiled from the logbooks are known to be biased by billfish (Istiophoridae) misidentifications. The initial step entailed fitting a generalized additive model (GAM) of blue marlin catch to environmental and operational data gathered by fishery observers during 8397 longline sets deployed by commercial vessels. The GAM included nine significant predictors and explained 41.1% of the deviance of observed blue marlin catches. The GAM coefficients were then applied to the corresponding predictors in the logbook reports from unobserved sets to estimate catches in evaluations of the accuracy of data from unobserved sets ( N = 87 277 longline sets on 8437 trips; 95.4% of unobserved effort). This was done by regressing the logbook catch data on the predictions, using the residuals to identify trips with systematic misidentifications, and then checking their logbooks against sales records from the public fish auction in Honolulu. The large majority of the misidentifications consisted of striped marlin, Tetrapturus audax , reported as blue marlin, with lesser numbers of shortbill spearfish, T. angustirostris , logged as blue marlin, and blue marlin logged as either striped marlin or black marlin, M. indica . An estimate obtained by use of the GAM and observer data indicated that the nominal catch of blue marlin was inflated by 29.4%. The 95% prediction limits about the GAM-generated estimate (34 201–41 507 blue marlin) did not include the catch total from the logbooks (48 911 blue marlin). The corrections also refined understanding of the distribution of blue marlin by reducing the impression that large numbers of blue marlin are sometimes caught north of Hawaii in the autumn and early winter months. There was no evidence of widespread underreporting of marlins. We conclude that this study significantly improved the accuracy of logbook data for blue marlin and should also contribute to improved understanding of the ecology and distribution of blue marlin. We infer that self-reporting could yield accurate marlins catch data if species identifications were improved because there was no apparent underreporting problem. Finally, we recommend that logbook data accuracy receive serious attention in the context of stock assessments.

Persistent Pelagic Habitats in the Baja California to Bering Sea (B2B) Ecoregion

The Baja California to Bering Sea (B2B) Marine Conservation Initiative seeks to establish a network of Marine Protected Areas within the Exclusive Economic Zones of the NAFTA countries- Canada, Mexico, and the United States. This network is designed to capture ecologically significant habitat for marine species of common conservation con- cern and pelagic regions of high productivity, with due consideration for the inter-annual sea surface temperature fluc- tuations of the El Nino Southern Oscillation (ENSO). Here, we present analytical methods that define pelagic habitat based upon the density of steep temperature gradients, or fronts, and we quantify their spatial and temporal persist- ence over a single ENSO cycle (1996-1999) to benefit marine conservation and marine management strategies. We find that less than 1% of the Northeast Pacific ocean exhibits a persistent ( > 8 mo/yr) concentration of tem- perature fronts (> .2km/km 2 ) within and between years. The Baja California Frontal System (BCFS) is the largest con- centration found within the multinational federal waters, between 0 and 300 km east of Baja California Sur. The BCFS appears more active under La Nina conditions, while the next largest persistent concentration, North Pacific Transition Zone, appears more active under El Nino conditions. We demonstrate habitat functions associated with the BCFS for blue whales (Balaenoptera musculus), swordfish (Xiphias gladius), and striped marlin (Tetrapturus audax). We recommend management and protection for this pelagic hotspot to the Mexican government and the tri-national Commission for Environmental Cooperation.

Cone visual pigments and retinal mosaics in the striped marlin

Three different cone photoreceptor visual pigments in the retina of striped marlin Tetrapturus audax were found with the aid of microspectrophotometry. This provides the first evidence for the basis of colour vision in the Istiophoridae. Furthermore, regional variations in photoreceptor density, type and spatial arrangement indicate differing visual capabilities along different visual axes.

Growth and length-weight relationship of the striped marlin, Tetrapturus audax (Pisces: Istiophoridae), in Cabo San Lucas, Baja California Sur, Mexico

To determine the age, backcalculate the length, and describe the individual growth and length-weight relationship of the striped marlin Tetrapturus audax, the catch of the sport-fishing fleet from Cabo San Lucas, Mexico, was sampled from 1988 to 1993. The length and weight of 1044 fishes were measured, and the fourth spine of the dorsal fin was collected from 399 of them. The mandibular length (ML) ranged from 156 to 263 cm, and the total weight (TW) ranged from 26 to 100 kg. No significant differences were detected (P &gt; 0.05) in the ML-TW relationship either between sexes or between years. The general relationship was TW = 0.00008*ML(2.523), showing a negative allometric growth (b &lt; 3, P &lt; 0.05). Ten age groups were determined (2 to 11). The relationship between ML and the dorsal fin radius was highly significant (P &lt; 0.001), justifying the use of the dorsal fin for the age determination and to describe the growth of the striped marlin. The von Bertalanffy growth model was fitted appropriately to backcalculated ML-age data (r2 = 0.99) and the values of the parameters were: L∞ = 221 cm, K = 0.23 per year, and t0 = –1.6. The striped marlin reaches 45% of the asymptotic length in its first year of life; in the second year the growth rate decreases to 10%, and during the next eight years the growth rate is 4% on average. The present study is the first to report on the individual growth of the striped marlin based on age determination in hard structures.

Global overview of the major constituent-based billfish tagging programs and their results since 1954

Release and recovery files from the world's five major constituent-based billfish (Istiophoridae) tagging programs were assembled into a single composite database. Data sources included the National Marine Fisheries Service's (NMFS) Cooperative Tagging Center (MIA) in the Atlantic Ocean, the NMFS's Cooperative Billfish Tagging Program (LJA) in the Pacific and Indian Oceans, the Australian Cooperative Tagging Program in the Pacific and Indian Oceans, the New Zealand Cooperative Game Fish Tagging Program in the Pacific Ocean, and The Billfish Foundation's (TBF) tagging program in the Atlantic, Pacific and Indian Oceans. Results for the main target species, including black marlin (Makaira indica), blue marlin (Makaira nigricans), white marlin (Tetrapturus albidus), striped marlin (Tetrapturus audax) and sailfish (Istiophorus platypterus) were compared and contrasted based on species, ocean body and tagging program. A total of over 317 000 billfish have been tagged and released, and 4122 have been recovered since 1954. Tag recovery percentages were generally higher for a recently developed double-barb nylon anchor tag compared with the typically used stainless steel dart tag. Greatest distances moved were largest for blue marlin and black marlin, followed by striped marlin, white marlin and sailfish. The TBF program had the highest tag recovery percentages for white marlin (2.4%) and blue marlin (1.7%), whereas the MIA program had the highest percentage recovery for sailfish (1.8%). The LJA program had the highest recovery percentages for black marlin (1.9%) and striped marlin (1.4%). The annual number of releases and recoveries for each target species tended to increase over the time series, particularly during the last decade. Cyclic annual movement patterns and/or seasonal site fidelity were evident for black marlin and white marlin. The data suggest that tag recovery percentages can be affected by tag type, reporting rate, localized fishing activities, outreach activities, and a variety of logistical issues indirectly related to size of ocean body. The efficiencies of the tagging programs are compared and recommendations are made to improve the programs. The composite tagging database provides the opportunity for a more comprehensive evaluation of the data and tagging programs than has previously been possible by examining the individual programs in isolation. The main advantage of constituent-based tagging programs is that large numbers of billfish can be tagged at a minimum cost. The main drawbacks are a lack of control over the tagging event and return of recovery data. Constituent-based tagging programs provide essential data on billfish movement and biology, and should be expanded and improved to meet the increasing need for this information.