bluuebunny/crossref_metadata_2025 huggingface dataset:
Plesiozela, gen. nov. from temperate South America: apparent sister-group of the previously known Heliozelidae (Lepidoptera : Incurvarioidea : Heliozelidae)
Authors: Karsholt Ole , Kristensen Niels P.
Published: August 2003

Plesiozela, gen. nov. is described from temperate South America, including two species P. nielseni, sp. nov. and P. patagonica, sp. nov. The adult moths, including their genitalia, are described and figured and the systematic position of the new genus within the family is discussed. Plesiozela considered to represent the sister-group of a clade comprising all previously known heliozelid genera, from which it differs in retaining a cephalic vestiture of exclusively erect piliform scales and long, folded and 5-segmented maxillary palps.
Systematics of the longicorn beetle genus Coptomma Newman (Coleoptera : Cerambycidae : Cerambycinae)
Authors: Song Deping , Wang Qiao
Published: August 2003

Longicorn beetles of the New Zealand genus Coptomma Newman are associated with a wide range of both native and exotic tree genera and are of some economic importance in forestry and horticulture because they kill leading shoots and degrade sawn timber. In this paper, the genus is revised and its scope is redefined. The genus Navomorpha White is synonymised with Coptomma. Two species, N. textorium and N. philpotti, are synonymised with Coptomma lineatum (Fabricius). A new species, C. marrisi, is described for Coptomma. All known species are redescribed. As a result of this revision, the present number of species in Coptomma has increased to five: C.�variegatum, C. lineatum, C. sulcatum, C. sticticum and C. marrisi. A key to species is given. Terminalia of both sexes are illustrated and described. The phylogeny of species is analysed cladistically and the monophyly of the genus is confirmed. Coptomma is widely distributed on the North Island, South Island, Stewart Island and Three Kings Islands of New Zealand. Known biology is noted for each species. The distribution of each species is mapped and discussed.
Two new genera of geoplaninid land planarians (Platyhelminthes : Tricladida : Terricola) of Brazil in the light of cephalic specialisations
Authors: Carbayo F. , Leal-Zanchet A. M.
Published: August 2003

Two new genera of geoplaninid land planarians are described. Cephalic specialisations, mainly external morphology and musculature development, partially define each genus. Cephaloflexa, gen. nov. shows some peculiar characteristics, such as a gradual narrowing of the anterior third of the body and an upwards roll of the anterior tip, the absence of eyes and sensory pits on the apex, and the existence of a retractor muscle derived from the ventral cutaneous longitudinal musculature. Geoplana bergi Graff, 1899 is allocated to Cephaloflexa and is designated as the type species. The ventral cutaneous longitudinal muscles of Supramontana, gen. nov. (monotypic), are partially sunk into the mesenchyme, thus constituting a cephalic retractor muscle. A new species of each genus is also described. The external morphology and anatomy of the cephalic region of the new genera and of Geoplana Stimpson, 1857, Choeradoplana Graff, 1896 and Issoca C. G. Froehlich, 1955 are analysed. Emendations to the diagnoses of Issoca and Choeradoplana are proposed based on cephalic differentiations.

Spanish abstractSe decriben Cephaloflexa, gen. nov. y Supramontana, gen. nov., dos nuevos géneros de planarias terrrestres de la subfamilia Geoplaninae, ambos caracterizados por especializaciones cefálicas, como la morfología externa y el desarrollo muscular. Se describe una nueva especie de cada género. Se transfiere Geoplana bergi Graff, 1899 para el género Cephaloflexa y se la designa especie tipo. Cephaloflexa, gen. nov. presenta características peculiares, como el tercio anterior del cuerpo muy fino, región anterior enrollada hacia el dorso, ausencia de ojos y fosetas sensoriales en el ápice anterior del cuerpo, y un músculo retractor derivado de la musculatura subcutánea longitudinal ventral. Supramontana, gen. nov., género monotípico, tiene parte de la musculatura subcutánea longitudinal ventral hundida en el mesénquima y transformada en la región anterior en un músculo retractor cefálico. Se analiza la morfología externa y la anatomía de la región cefálica de Geoplana Stimpson, 1857, Choeradoplana Graff, 1896 e Issoca Froehlich, 1955 y se proponen enmiendas a las diagnosis de Choeradoplana e Issoca basadas en las diferenciaciones cefálicas.
Likely impacts of an eastward expansion of the inshore gill-net fishery in the Western Cape, South Africa: implications for management
Authors: Hutchings K. , Lamberth S. J.
Published: August 2003

Current South African government policy aims to create more equitable access to marine resources and there is pressure to increase the inshore gill-net fishing effort. At present, the gill-net fishery in the Western Cape is confined to the cool temperate west coast. In order to ascertain the potential catch if the fishery was to expand along the warm temperate south-west coast, a program of experimental netting was conducted. Estuarine and coastal marine sites were sampled bimonthly, using a range of commercial gill-nets (44–178 mm stretch-mesh). Although the target species, Liza richardsonii, dominated the catches, at least 33 of the by-catch species caught were also targeted by the commercial or recreational line-fish sectors. The number of species captured and the line-fish (by-catch) catch per unit effort (CPUE) were greatest in areas currently closed to the commercial gill-net fishery. Multivariate analysis indicated significant differences in catch rates and composition between exploited west coast and unexploited south-west coast sites. A combination of natural biogeographical trends and the impact of over 100 years of commercial gill-netting on the west coast are the likely causes of these differences. A spatial expansion of the gill-net fishery could have a detrimental impact on overexploited line-fish stocks and lead to increased user conflict.
Swimming behaviour and migration of a swordfish recorded by an archival tag
Authors: Takahashi Mio , Okamura Hiroshi , Yokawa Kotaro , Okazaki Makoto
Published: August 2003

An archival tag equipped with sensors for temperature, depth and luminous intensity is an excellent method to elucidate behaviour and migration of marine organisms. Herein, what we believe is the first successful archival tag experiment with swordfish in the world is reported. The swordfish, which was harpooned with an archival tag encased in a plastic capsule, was released in July 1999 off the east coast of Japan. The fish was recaptured by a harpoon fishing vessel in June 2000, only 103 km from the tagging location and weighed approximately 120-kg. By comparing the water temperature data of the archival tag with oceanographic data, a cyclic seasonal migration between the food-rich Oyashio cold current area (40–45°N) during summer and the subtropical wintering area (10–20°N) was suggested. During most of the days of observation and for the majority of the time within a day, tagged fish swam in cold water (3–6°C) and deeper than approximately 200 m; at night, fish generally stayed near the warmer surface waters (21–27°C). The greatest swimming depth was approximated to be 900 m, deduced from ambient water temperature data. The swimming depth and behaviour pattern changed in response to the ambient water temperature.
Stock assessment of blue marlin (Makaira nigricans) in the Pacific using MULTIFAN-CL
Authors: Kleiber Pierre , Hinton Michael G. , Uozumi Yuji
Published: August 2003

In the Pacific, blue marlin are an incidental catch of longline fisheries and an important resource for big game recreational fishing. Over the past two decades, blue marlin assessments by different techniques have yielded results ranging from an indication of declining stock to a state of sustained yield at approximately the maximum average level. Longline fishing practices have changed over the years since the 1950s in response to changes in principal target species and to gear developments. Despite increasingly sophisticated attempts to standardize fishing effort with changing fishing practices, the stock assessments to date are likely confounded to a greater or lesser degree by changes in catchability for blue marlin. Yet, only data from commercial longline fisheries targeting tuna provide sufficient spatial and temporal coverage to allow assessment of this resource. To re-assess the blue marlin stocks in the Pacific and also to assess the efficacy of a habitat-based standardization of longline effort, a collaborative analysis was conducted involving scientists at the National Research Institute of Far Seas Fisheries, Shimizu, Japan, the Inter-American Tropical Tuna Commission, La Jolla, California, and the NOAA Fisheries Honolulu Laboratory, Honolulu, Hawaii. Using MULTIFAN-CL as an assessment tool, there was considerable uncertainty in quantifying the fishing effort levels that would produce a maximum sustainable yield. However, it was found that, at worst, blue marlin in the Pacific are close to a fully exploited state, that is the population and the fishery are somewhere near the top of the yield curve. Furthermore, it was found that effort standardization using a habitat-based model allowed estimation of parameters within reasonable bounds and with reduced confidence intervals about those values.
Pelagic fisheries catching blue and striped marlins in the US Western Pacific islands
Authors: Dalzell P. , Boggs C. H.
Published: August 2003

Various pelagic fisheries in the US Western Pacific islands capture blue and striped marlins. Total catches by US vessels in the Western Pacific islands amount to about 2000 t for blue marlin and 600 t for striped marlin, or 9% and 5% of the nominal total Pacific-wide catch of these two species, respectively. Catch records for domestic Western Pacific fisheries typically extend over several decades, although in this short communication they are confined to blue and striped marlin catches in the 1990s. There are currently no specific management measures for marlins in the US Western Pacific islands, but other management measures for US pelagic fisheries in this region may have an influence on marlin catches.
Historical perspective of global billfish stock assessment
Authors: Uozumi Yuji
Published: August 2003

In spite of the substantial increase in information on billfish over the last decade, especially in the landing and catch per unit effort data, statistics for some of the commercial and recreational fisheries, basic biological information on billfish such as on growth, maturation, catch at age, and sex ratio by size, is still insufficient for the application of more data-demanding models. A family of production models is still the major tool for the stock assessment of billfish. Although there are significant increases in information on catch per unit effort, it is still hard to obtain solutions from these models in many cases without putting subjective constrains on the model parameters. In addition to the uncertainty in catch information, major uncertainty in the results of stock assessments comes from the difficulties in the realistic estimation of effective fishing effort for each fishery harvesting billfish. Those difficulties arise mainly from operational changes in the fishing and partial coverage of geographical distribution of billfish by the fisheries. It is very hard to overcome these problems only by improvement of the fishery-dependent statistics. Additional information on habitat preferences of billfish and the vertical distribution of longline gears, facilitated by the newly developed equipment such as pop-up archival tags and small time-depth recorders, is very useful to evaluate gear efficiency and stock availability to fishing gear. The assessment of billfish will be improved by the habitat-based standardization models utilizing these additional data..
Sailfish movement in the Arabian Gulf: a summary of tagging efforts
Authors: Hoolihan John
Published: August 2003

In Arabian Gulf waters of the United Arab Emirates, sailfish (Istiophorus platypterus) are seasonally resident from October through April. Recreational anglers started occasional, self-initiated tagging in 1983. Tags originating from one local and five foreign agencies have been infixed. Early tagging and recovery data was often obscure or lost. In 1997, a concerted effort to understand migration cycles began by consolidating tagging practices and monitoring tag recoveries. Conventional dart tags were infixed on 1871 sailfish from 15 April 1996 to 21 April 2001. Recovered tags (n = 92), as of 16 July 2001, indicated a recapture rate of 4.91%. Of these, 90.21% (n = 83) were recovered during May/June in Iranian waters and represent springtime migratory movement leading north-west, further into the Gulf. Time-at-large for all recaptures ranged from 17 to 1148 days, while point-to-point travel extended from 2.5 to 697 km. Sailfish recaptured in the same year (n = 59) and exhibiting migratory movement travelled a mean distance of 474 km. Location of sailfish during late July through September is unknown, owing to deficiencies in tag recoveries, catch data and anecdotal information. The use of pop-up satellite tags is underway to address this question.
Tests of the robustness of habitat-standardized abundance indices using simulated blue marlin catch - effort data
Authors: Goodyear C. Phillip
Published: August 2003

This paper describes a computer model designed to simulate longline catch–effort data, and to test the robustness of methods to standardize the relative catch per unit effort (CPUE) abundance index. The model considers abundance and catch by month, area and depth based on the temperature habitat of the species. Characteristics of fishing gears are used in a submodel to predict catch rate by set and depth. An application to an Atlantic blue marlin bycatch fishery from 1956 to 1999 is presented. The depth distributions of sets, the propensity of marlin to bite stationary moving baits, and the assumed habitat preferences were each varied. The simulated CPUE series were standardized using both habitat-based and General Linear Models (GLM). Unstandardized CPUE trends were strongly biased. The GLM standardizations accurately reflected trends in the simulated population. The habitat standardizations proved accurate when the assumptions used in the analysis were precisely correct, but were often strongly biased when the assumptions were inaccurate. These results suggest that habitat standardization of CPUE time series is potentially useful if there is accurate knowledge of the distributions of the population, the actual fishing depths of the gears and factors that may affect the fish's propensity to take bait. Absent certain knowledge of these factors, the habitat approach to standardization should be used with great caution.
Blue marlin mean length: simulated response to increasing fishing mortality
Authors: Goodyear C. Phillip
Published: August 2003

Mean length of caught fish often declines noticeably with increased fishing mortality and this trend is regarded as an indicator of excessive fishing mortality. The most recent stock assessment results for Atlantic blue marlins and Atlantic white marlins indicate that these stocks are heavily overfished. However, available data do not suggest a strong trend of decreasing lengths of marlins in the catch. The lack of such a trend has been used to argue that the assessment results are in error. This study uses population simulation to characterize the expected response of the size distribution of blue marlin to the vector of fishing mortality and FMSY estimated for the base case in the most recent stock assessment, and contrasts the results with a similar analysis for Atlantic swordfish. The results indicate that blue marlin should not be expected to exhibit strong trends in mean length with respect to fishing mortality within the range of fishing mortality estimated in the most recent stock assessment, and that the trends in the observed size composition are consistent with the findings of the stock assessment. The findings indicate that declining mean length is not a necessary outcome of excessive fishing mortality in all species.
Spatio-temporal distribution of longline catch per unit effort, sea surface temperature and Atlantic marlin
Authors: Goodyear C. Phillip
Published: August 2003

Atlantic blue and white marlin are currently overfished, primarily as a result of bycatch in pelagic longlines directed at other species. One possible management measure to reduce fishing mortality on these species would be to restrict fishing effort in times and places with exceptionally high marlin catch per unit effort (CPUE). The International Commission for the Conservation of Atlantic Tunas maintains a database of catch and catch-effort statistics of participating nations. These data were analysed to determine whether the distribution of CPUE is sufficiently heterogeneous in time and space that such measures might provide meaningful management alternatives. The resulting distributions of catch rates were also contrasted with monthly average sea surface temperatures to examine the possible association between temperature and CPUE. The results show spatio-temporal heterogeneity in catch rates that may be partly explained by seasonal changes in sea surface temperatures. The time–area concentrations of high CPUE differ between the species. This observed heterogeneity might be exploited to develop alternatives for reducing fishing mortality for future management of the fisheries, but additional research is needed to refine the spatial scale of the analysis and to more fully understand the factors contributing to the observed distribution.
Analysis of sportfishing catch rates of striped marlin (Tetrapturus audax) at Cabo San Lucas, Baja California Sur, Mexico, and their relation to sea surface temperature
Authors: Ortega-García Sofía , Klett-Traulsen Alexander , Ponce-Díaz German
Published: August 2003

Cabo San Lucas, Baja California Sur, Mexico, is the main sportfishing location for striped marlin, with a mean annual catch rate of 0.6 fish per fishing trip. In the present study, the interannual and seasonal variation of sportfishing catch rates from 1990 to 1999, and their relationship to mean monthly sea surface temperatures were analysed. Although interannual variation was not significant, the seasonal effect showed significant differences, with highest average catch rates in winter, and lowest catch rates in summer (0.9 and 0.3 respectively). An interannual significant difference with a decreasing tendency was in length analysis. Significant length and weight differences were found between males and females. Among females, the heaviest fish were recorded during spring. A significant relationship between catch rate and sea surface temperature (r = –0.62) was found, but no significant changes of catch rates could be measured during the 1992–1993 and 1997–1998 El Niño Southern Oscillation events, in spite of an apparent catch rate increase during the spring of 1998. Highest catch rates were recorded at between 22 and 24°C.
Recreational billfish catches and gamefishing facilities of Pacific Island nations in the Western and Central Pacific Ocean
Authors: Whitelaw Wade
Published: August 2003

Gamefishing is a developing industry for many of the Pacific Island nations, with a number of countries encouraging the industry with tax relief and tourism promotion. This paper was prepared to provide a preliminary appraisal of gamefish facilities and recreational billfish catches of Pacific Island countries in the Western and Central Pacific Ocean. The level of development of gamefishing varies among Pacific Island nations, with fishers of some countries only carrying out subsistence fishing (including billfish), whereas others have a well-developed gamefishing infrastructure. The gamefish facilities of each country are described, including charter operations, number of private vessels and berthing facilities. Estimates of recreationally caught billfish are also provided for each Pacific Island nation. These estimates have been facilitated by the development of a gamefish catch and effort database by the Secretariat of the Pacific Community. Presently, an estimated 1050 metric tonnes of marlin are caught by gamefishing in the Western and Central Pacific Ocean, which compares with an estimate of around 18 000 metric tonnes caught by commercial longline and purse seine vessels.
Marlin fisheries management in Australia
Authors: Findlay James D. , Cross Colleen M. , Bodsworth Andrew G.
Published: August 2003

Australia has a relatively long history with respect to management of fishery interactions with marlins. Sectoral conflict has been, and remains, the main driver of management action. Whilst constrained by verified catch and effort data from both recreational and commercial sectors, a range of management actions including limited entry, non-retention, non-targeting, closed areas and gear restrictions are reviewed. The review of management performance shows that the effectiveness of management actions varies considerably. Some measures such as voluntary non-retention policies have had little impact, whereas others such as closed areas have had a marked impact on fishery interactions and sectoral conflict. Relatively small areaclosures reduced the interactions of Japanese longliners with black marlin by 85%. On a per unit-of-effort basis marlinsare currently afforded greater protection than ever from overfishing; however, effort from all sectors continues to increase and sectoral conflict with respect to marlins is expected to continue to result in calls for further management action.
Managing Atlantic marlin as bycatch under ICCAT. The fork in the road: recovery or collapse
Authors: Peel Ellen , Nelson Russell , Goodyear C. Phillip
Published: August 2003

Atlantic billfish (marlin, sailfish and spearfish) are managed under the jurisdiction of the International Commission for the Conservation of Atlantic Tunas (ICCAT). Because they are not commonly a target species, most fishing mortality is generated as a function of bycatch in various commercial fisheries. Billfish are very important species for recreational fisheries. The record indicates that ICCAT has placed its greatest emphasis on managing target fish to maximize their catch for ‘food purposes’ and has not placed the same level of emphasis on maximizing catch for ‘other purposes’, such as for the benefit of recreational fisheries.Stock assessments indicate Atlantic marlin are severely overexploited, with the rates of decline showing no signs of slowing. The primary source of billfish mortality is as bycatch in pelagic longline fisheries for tuna and swordfish. Simultaneous fishing mortality rates that will produce maximum sustainable yield (MSY) for at least one targeted tuna species is near the extinction rate for blue marlin. Failure to significantly reduce fishing mortality on marlin by restraining effort on target species has led to the collapse of both blue and white marlin stocks and, if continued indefinitely, may lead to extinction of either species. Although ICCAT's charter does not prioritize management between different types of fisheries, commercial or recreational, or among different species of fish within its authority, the de facto result of ICCAT's actions to date has relegated billfish to the role of bycatch species. The needs of the directed recreational billfish industry have been largely ignored.In the absence of responsible action by ICCAT to reduce fishing mortality on marlin, those concerned with the conservation of billfish will be forced to seek alternative conservation and management assistance through The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and other protected species options. Compatible management solutions now must be identified and implemented by ICCAT if diverse fishing interests are to coexist and the stocks are to return to MSY. Time and area closures and live releases, coupled with some restraints on targeted effort, may offer a solution most acceptable to all fishing interests.
Relationship between catch, effort, CPUE and local abundance for non-target species, such as billfishes, caught by Indian Ocean longline fisheries
Authors: Fonteneau Alain , Richard Nicolas
Published: August 2003

This paper analyses the local relationship between effort, catches, catch per unit effort (CPUE) and abundance of target species (such as tunas) and of non-target species (such as billfishes). The Indian Ocean longline fisheries are taken as an example. This paper evaluates the potential bias in the relationship between local CPUE and abundance when fisheries are increasing their fishing effort. A presentation of the Indian Ocean longline fisheries is carried out. A statistical analysis of CPUE is conducted using a generalized additive model which tends to indicate that the local effort is an important component in the statistical behaviour of the local CPUE. A migratory model in which both resources and fisheries are mobile was built. This model simulates the combined exploitation of two species, a target and a bycatch species, both fished at increasing intensity. This model confirms the potential bias as a result of the concentration of fishing effort in areas of high density of the target species. It also suggests that the CPUE of bycatch species may be more heavily biased because of their status. It is recommended that local fishing efforts should preferably be taken into account in order to calculate the CPUE of both target and non-target species.
Monitoring the recreational gamefish fishery off south-eastern Australia
Authors: Lowry Michael , Murphy Jeff
Published: August 2003

The east coast Australian gamefish fishery is a diverse, multi-species fishery that targets billfish, sharks, tuna and other pelagic fish along the east Australian seaboard. A Gamefish Tournament Monitoring Program (GTMP) was undertaken, and 39021 angler trips from 1996 to 2000 were analysed. The program reports on trends in fishing effort, catch rates, catch composition, proportions of captures tagged and released and spatial distribution of catches for the principal recreational billfish species: black marlin (Makaira indica), striped marlin (Tetrapterus audax) and blue marlin (Makiara nigricans).The GTMP was principally designed as part of an integrated program to monitor the recreational gamefish fishery. The spatial and temporal design of the program restricted statistical analyses however, there were trends in fishing effort, directed effort, catch rates, catch composition, proportions of fish tagged and spatial distribution of catches for the principal recreational billfish species over seven successive years (1994–2000). Analysis of catch data, stratified by directed effort, indicated significant differences in catches of target species, demonstrating the importance of calculating catch rate estimates according to the main target preference. Analysis of tournament based tagging information indicated that while overall tournament tagging rates remained high (88%) there were significant differences in the number of fish tagged between species groups highlighting the impact that angler attitude and the competition point score structure has on the harvest of gamefish target species.
Mortality rate of striped marlin (Tetrapturus audax) caught with recreational tackle
Authors: Domeier Michael L. , Dewar Heidi , Nasby-Lucas Nicole
Published: August 2003

A project was initiated in the autumn of 2000 to document the mortality of striped marlin caught on recreational fishing tackle, with a follow-up study conducted in autumn of 2001. Fish were caught using typical recreational fishing methods and 80 pop-up satellite archival tags were deployed with new software and mechanical release mechanisms that allowed tags to detach and transmit early if the fish died. The first year study was also designed to compare the effectiveness and associated mortality of circle hooks versus J-hooks, while the second year study compared offset and non-offset circle hooks. All fish were caught on live bait. Circle hooks were found to be equally effective in hooking and landing striped marlin and far less likely to cause serious bleeding or become lodged in areas other than the mouth. Non-offset and 5° offset circle hooks had very similar performance. Depth and temperature records allowed us to determine the fate of individual marlin following release. In total, 16 of 61 fish died (mortality rate of 26.2%), all within 5 days of release (mean 1.5 days). Injury was a clear predictor of mortality; 100% of fish that were bleeding from the gill cavity died, 63% of fish hooked deep died, and 9% of those released in good condition died.
Factors affecting striped marlin catch rate in the New Zealand recreational fishery
Authors: Holdsworth John , Saul Peter , Browne Gene
Published: August 2003

A 25-year time series of striped marlin catch per unit effort (CPUE) data has been collected from gamefish charter skippers fishing the north-east coast of New Zealand. The CPUE averaged over the whole gamefishing season ranged from 0.053 striped marlin per charter boat day in 1984–1985 to 0.269 striped marlin per charter boat day in 1998–1999. This study investigates the amount of the variability in gamefish charter CPUE that can be explained by environmental and fishing-related factors for the period 1981–1997. Factors investigated were sea surface temperature during the fishing season, El Niño southern oscillation index, the position of the 20°C isotherm at the beginning of the fishing season, annual commercial catch of striped marlin in the New Zealand 200 mile zone and surface longline CPUE in the wider south-west Pacific. A stepwise multiple regression was used to develop a model of recreational striped marlin CPUE to determine the factors that best accounted for the variation observed. Surface longline CPUE in the general south-west Pacific (10°S–40°S latitude, 165°E–160°W longitude) had the strongest correlation with recreational CPUE (P = 0.001), but a poor correlation was found with longline CPUE from the western Tasman Sea and Coral Sea (10°S–40°S latitude, 145°E–165°E longitude). The total surface longline catch of striped marlin in New Zealand each season was negatively correlated with recreational CPUE (P = 0.019), which indicates a possible interaction between these fisheries.
Evidence of blue marlin, Makaira nigricans, spawning in the vicinity of Exuma Sound, Bahamas
Authors: Serafy Joseph E. , Cowen Robert K. , Paris Claire B. , Capo Thomas R. , Luthy Stacy A.
Published: August 2003

Exuma Sound is a semi-enclosed body of water bounded by islands of the Bahamas. During July 2000, sampling for larval billfish was carried out throughout the Sound's surface waters as well as in adjacent open waters of the Atlantic Ocean. A total of 99 larval billfish (Istiophoridae) was collected. Ninety of the larvae were identifiable as blue marlin (Makaira nigricans) and three as sailfish (Istiophorus platypterus). The remaining larvae were also istiophorids, unidentified to species owing to damage; no larval Xiphias gladius were collected. Larval blue marlin densities ranged from 0 to 3.4 larvae/1000 m2; their sizes ranged from 3.1 mm notochord length to 22.6 mm standard length. Densities tended to be highest north-east of the Sound's central axis, especially within the two regions where exchange with the Atlantic is greatest. Mean densities tended to decrease in the direction of mean flow; mean lengths increased from 8.08 mm at the Sound's mouth to 14.7 mm standard length at its upper reaches. Length-based estimates of larval age ranged from 2.2 to 17.2 days. Given these age estimates and assuming passive surface transport, the blue marlin larvae collected were likely the result of recent spawning in waters that include Exuma Sound and may extend some 200 km south-east of its mouth. This study suggests that Exuma Sound functions as a nursery area for blue marlin, and possibly other billfish species, at least during the summer. Limited sampling just outside Exuma Sound, in the Atlantic Ocean proper, also yielded blue marlin larvae.
Historical development of recreational billfishing in Bermuda and the significance of catches of large blue marlin (Makaira nigricans)
Authors: Luckhurst Brian E.
Published: August 2003

Directed fishing effort for blue marlin (Makaira nigricans) and white marlin (Tetrapterus albidus) in Bermuda commenced in the early 1970s. The first annual billfish tournament was held in 1974. This 4-day tournament has been held every year since its inception and, with improvements in charter fishing vessels and fishing gear, local captains have become increasingly proficient at catching marlin. The development of a strong billfish conservation movement in the mid-1980s in the tropical western Atlantic promoted tag and release of marlin. This conservation ethic has been translated into a mean release rate in Bermuda of 91.6% for blue marlin and 97% for white marlin over the past 15 years. The billfish tournament has become primarily a release event, owing to the 227-kg (500 lbs) minimum weight for landing blue marlin. The catch of a blue marlin weighing 512 kg (1130 lbs) in 1984 gave Bermuda prominence in the billfishing world at that time. Since that event, an additional eight blue marlin weighing over 454 kg (1000 lbs) have been caught in Bermuda, giving the island a reputation as a primary site for catching large fish. This has had socio-economic benefits for the island, as foreign anglers contract local charter fishing vessels in search of a trophy blue marlin and foreign fishing boats come to fish Bermuda waters with attendant economic benefits for the island.
Use of charter boat data to infer the annual availability of black marlin, Makaira indica, to the recreational fishery off Cairns, Australia
Authors: Campbell Robert A. , Pepperell Julian G. , Davis Timothy L. O.
Published: August 2003

Catch data, recorded in daily diaries kept by the captains of charter boats in the recreational fishery that targets black marlin (Makaira indica) in the Cairns/Lizard Island region off north-eastern Australia, were used to calculate annual indices of fishing success (catch per day). Generalized Linear Models were used to investigate factors likely to influence catch rates, such as captain, area fished, water temperature, moon phase and the strength and direction of prevailing currents. Despite a high degree of inter-annual variability in the catch, results indicate that there has been a long-term decline of between 20–30% in estimated availability between 1970 and 1997. Models fitted to the data for the period 1987–1996 indicate that several environmental factors can have a significant influence on availability in any given year, with higher catch rates occurring close to a half moon and associated with water temperatures around 26.0–26.5°C. Catch rates for the period 1980–1997 were also found to be negatively correlated with longline effort levels within the inshore region close to the recreational fishery, though this correlation was not found to be significant.
Age and growth of black marlin, Makaira indica, in east coast Australian waters
Authors: Speare Peter
Published: August 2003

Sagittae, anal and dorsal fin spines were collected from black marlin, Makaira indica, in eastern Australian waters to evaluate and interpret age information from these structures. Presumed annual marks in sections of the third anal and third dorsal spines from 69 fish ranging in size from 8.5 to 451 kg were examined. Sectioned otoliths were also examined for presumed daily microincrements using both light and scanning electron microscopy. Spine radius and sagitta weight each varied predictably with the length and weight of the fish. The time period between consecutive growth marks was checked against the growth of these hardparts recovered from a tetracycline-injected and recaptured fish at large for 6 months. The increase in the size of fin spines from the recaptured fish was consistent with calculated growth curves derived from counts of presumed annual zones. Lengths and weights at age, based on these bands, are presented for black marlin. External ridges were observed on the edge and ventral surface of the rostrum of the sagitta, but they were inconsistently clear to be reliably counted. Sagittae displayed an internal record of microincremental growth on a scale that suggested a daily periodicity. Confident and consistent enumeration of these increments was restricted to fish <40 kg (~1600 mm lower jaw–fork length). A daily cycle of increment deposition was not confirmed by a count from the recaptured fish that fell short of the 198 days at large. The discrepancy was most likely associated with the difficulties of enumerating microincrements. The ages assigned to black marlin in this study support ages suggested from analysis of length–frequency data on juvenile fish. They underline the restraints previously recognized in decoding sagittae of blue marlin and confirm the utility of fin spines in providing age information for istiophorids.
Status of swordfish stocks in the eastern Pacific Ocean estimated using data from Japanese tuna longline fisheries
Authors: Hinton Michael G.
Published: August 2003

Swordfish (Xiphias gladius) are harvested in target and non-target fisheries throughout the eastern Pacific Ocean (east of 150°W). Analyses of trends in catch rates (catch per unit effort) standardized using general linear models indicate that there are two stocks in the eastern Pacific Ocean that have a north–south boundary at 5°S latitude; this is in striking contrast to the 10°N boundary that has generally been assumed by previous studies. Trends in standardized catch per unit effort have held relatively level for the north stock and have been increasing for the south stock. Considering these trends and given that annual catches have been fairly stable in the region since 1989, it appears that swordfish are not overfished in the eastern Pacific Ocean. Given the potential for rapid change in the nature of those gill-net and longline fisheries that are increasingly targeting swordfish in the region, the trends in standardized catch per unit effort should be closely monitored for indications of changing status of these stocks.
Social and economic perspective on recreational billfish fisheries
Authors: Ditton Robert B. , Stoll John R.
Published: August 2003

At the Second International Billfish Symposium in Kona, it was reported that little was known about the social and economic aspects of recreational billfish fisheries. There was plenty of background, some good questions, but few answers. There had been little history of social science involvement in fisheries management at the time and even less in billfish fisheries. Whether authorized or not, fishery management decisions worldwide are going to be made on the basis of ‘best available’ social and economic understanding. Unfortunately, the values held by many in the billfish angler community are not likelyto be well represented in the mix for various reasons. Research in the USA and in Latin America over the past 13 years hasprovided an understanding of the billfish angler constituency, its commitment to catch and release and support for resource conservation, its local and regional impacts on tourism economies, and its willingness-to-pay above andbeyond trip costs (a measure of user value) in the US Atlantic, Puerto Rico, Costa Rica and Mexico Pacific. Although knowledge of the recreational billfish fishery has improved, comparatively little is known about the social and economic benefits associatedwith commercial (direct and bycatch) billfish fisheries. With little more than dockside prices available in many localities, it is difficult to know their value in comparison with recreational fisheries and the possible trade-offs associated with various management measures. In addition to describing what is still not known, this paper will identify a future research agenda in this area.
Stock structure of the world's istiophorid billfishes: a genetic perspective
Authors: Graves John E. , McDowell Jan R.
Published: August 2003

Istiophorid billfishes are highly migratory species that inhabit the tropical and subtropical, epipelagic waters of the world's oceans, a large, relatively homogeneous environment that lacks significant physical barriers. Based on these observations alone, one would not expect marlins, sailfish and spearfishes to exhibit substantial stock structure. This assumption has been evaluated with a variety of techniques, including analyses of morphological characters, adult distribution, tag and recapture data, the spatial and temporal distribution of spawning and, recently, molecular genetic characters. This paper focuses on inferences of istiophorid billfish stock structure derived from investigation of several different classes of molecular markers, and reviews our current understanding of the genetic basis of stock structure of striped marlin, white marlin, blue marlin, sailfish and black marlin. Significant genetic differences exist between Atlantic and Indo-Pacific populations of blue marlin and sailfish, and the presence of distinct mitochondrial DNA lineages suggests that ocean populations were isolated in the past. However, the occurrence of identical genotypes in both oceans is evidence of recent genetic contact. The genetic data do not support recognition of separate Atlantic and Indo-Pacific species of blue marlin or sailfish. White and striped marlin are separated by about the same level of genetic divergence as Atlantic and Indo-Pacific populations of blue marlin and sailfish, but preliminary analysis of the mitochondrial DNA control region suggests that, unlike Atlantic and Indo-Pacific populations of blue marlin and sailfish, white marlin and striped marlin represent independent evolutionary units. If white and striped marlin are valid species, they are of very recent origin. Significant intraspecific genetic heterogeneity was found among collections of striped marlin and sailfish within the Indo-Pacific; both species exhibited a clear spatial partitioning of genetic variation among geographically distant collection locations. There was no genetic evidence for within-ocean population structuring for other istiophorids examined. Inferences of billfish stock structure derived from studies of molecular markers complement those obtained using other methods of analysis, and together these studies demonstrate substantial differences in the level of population structuring among istiophorid billfishes, information critical for effective management of these highly migratory species.
Use of minimum size regulations to achieve reduction targets for marlin landings in the Atlantic Ocean
Authors: Venizelos Arietta , Sutter Frederick , Serafy Joseph
Published: August 2003

Trends in US recreational catch and effort data for Atlantic blue marlin and white marlin from 1972 to 2000 are examined. A method for predicting and setting minimum size regulations for this fishery is described. Additionally, this paper re-examines the impact of the most recent minimum size increases on the US recreational fishery for Atlantic marlin. The effectiveness of setting minimum size limits as a primary management approach is discussed, as is the increase in catch and release fishing in the US recreational marlin fishery.
Alternative stable states in the aquatic vegetation of shallow urban lakes. I. Effects of plant harvesting and low-level nutrient enrichment
Authors: Morris Kay , Boon Paul I. , Bailey Paul C. , Hughes Leesa
Published: August 2003

Shallow urban lakes are often subject to chronic nutrient enrichment and their submerged plants are sometimes harvested to facilitate recreational use. The theory of alternative stable states predicts that: (i) low levels of nutrient enrichment should have little effect on the existing communities of submerged macrophytes in such lakes; but (ii) harvesting the plants should facilitate a shift to phytoplankton dominance. These two predictions were tested with large (3000 L), replicated mesocosms in a shallow urban lake densely colonized by the submerged angiosperm, Vallisneria americana Michaux. Harvesting V. americana substantially increased light penetration through the water column, but did not significantly increase phytoplankton biomass. Vallisneria americana regrew rapidly after harvesting and Chara species, which were previously absent, appeared in the harvested mesocosms. Chronic low-level nutrient enrichment significantly increased phytoplankton biomass (>100 μg chlorophyll a L–1) but not epiphyte biomass on the leaves of V. americana or on plastic leaf surrogates. The aboveground biomass and leaf area index of V. americana were not affected significantly by nutrient enrichment. The theory of alternative stable states successfully predicted the resilience of the submerged angiosperm community to low-level nutrient enrichment, but did not accurately predict the response to plant harvesting. The response of the lake vegetation to higher levels of nutrient enrichment is reported.
Alternative stable states in the aquatic vegetation of shallow urban lakes. II. Catastrophic loss of aquatic plants consequent to nutrient enrichment
Authors: Morris Kay , Bailey Paul C. , Boon Paul I. , Hughes Leesa
Published: August 2003

The theory of alternative stable states predicts that high nutrient concentrations increase the probability of shallow lakes switching from a state dominated by vascular macrophytes to one dominated by phytoplankton and/or other algae. In the first paper of this series it was demonstrated that chronic, low-level nutrient loading did not affect a switch across vegetation states. To test the possibility that higher nutrient loadings result in vegetation changes, replicated mesocosms (~3000 L) were placed in an urban lake densely colonized by Vallisneria americana Michaux, a submerged angiosperm, and were subjected to higher levels of chronic nutrient enrichment. Moderate and high nutrient loadings significantly increased phytoplankton biomass and produced extensive, dense mats of floating algae. Many mesocosms became covered by the floating fern Azolla pinnata R.Br. This reduced light penetration and concentrations of dissolved oxygen in the water column profoundly and resulted in the complete loss of V. americana from almost all nutrient-enriched mesocosms within 4 months. A catastrophic loss of submerged aquatic plants so rapidly after nutrient enrichment is a relatively novel experimental finding, particularly in terms of the likely mechanism; that is, shading and subsequent anoxia caused by dense mats of floating plants other than algae.