Dispersal of adult Black Marlin (Istiompax indica) from a Great Barrier Reef spawning aggregation

Full description

Adult and juvenile black marlin (Istiompax indica) were obtained between 1987 and 1991 from the recreational fishery operating along the Queensland coast, eastern Australia. Thirty males between 8.5 kg and 83.5 kg and 26 females (11.6-64 kg) were sourced from the nearshore fishing grounds off Cape Moreton, Dunk Island and Cape Bowling Green. Twenty five large females (295-525 kg) and 3 males (59-158 kg) were secured from the Lizard Island Game Fish Club's annual October tournaments off the Ribbon reefs.Date of capture, weight (kg), lower jaw-fork length (LJFL cm) and gonad weights (gms) were recorded for each specimen. Gonad tissue was routinely taken from the mid-section of a gonad, randomly left or right, and placed directly into 10% neutral buffered formalin solution. Histological sections were prepared and a software driven computer dissecting microscope was utilized for processing the histological sections to recover imagery, oocyte counts and measurements. Larval billfish sampling took place over several days in October and November 1988 and 1989 in the vicinity of the recreational fishing fleet supplying adult specimens for the reproductive component of this study. Sampling took place along the extent of embayments at First Corner and Second Corner on No. 10 Ribbon Reef and in a southerly facing embayment on Yonge Reef. The contents of the cod end of the net from each tow were preserved in 70% ethanol. Fish larvae were separated and retained from each sample for later identification of the billfish larvae. Measurement software and calibrated imagery were used to provide standard lengths for each larva to 0.1 mm following rehydration. Six larvae identified as black marlin based on visual characters were submitted to DNA analysis (400 bases of the mitochondrial DNA control region compared to known black marlin sequences). Larval black marlin were aged based on published age-length relationships and growth models for larval blue marlin. The smallest istiophorid larva recorded in this study was 1.7 mm and this value was used as size at hatching. An instantaneous growth rate of 0.0976 enabled calculated age estimates to be assigned to each larva. Between 2002 and 2009, a total of 67 Popup satellite archival transmitting (PSAT) tags were deployed on black marlin captured via rod-and-reel from recreational fishing boats fishing the GBR between Cairns and the Ribbon Reefs. Tags were deployed between September and December on fish assessed to be in good health after capture. Sea surface temperature (SST) records from the PSAT tags were used to determine the mean temperature experienced by black marlin within the study area. Daily SST values were obtained for each tagged fish remaining in the study area by accessing the PSAT transmitted temperature/depth data.To compliment the PSAT tag results, data on black marlin from the east coast of Australia, tagged using conventional tags were extracted from the tagging database owned and maintained by Industry and Investment NSW.
An integrated study of black marlin (Istiompax indica) reproductive biology, larval sampling and adult black marlin tagging was undertaken to provide evidence of spawning and to document the geographic range of the black marlin stock that frequents the GBR.

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Maintenance and Update Frequency: notPlanned

Statement: Statement: Processing of histological sections:Histological preparation employed staged alcohol dehydration and wax embedded tissue sectioned at 5 mm prior to staining with haematoxylin and counter-staining with eosin.Three areas from each histological slide preparation were randomly selected at 40X magnification and imaged for later counting of the observed development stages. Oocyte counts were made across each image and measurements (diameter) from a selection of oocytes at each stage of development. Singular measurement was constrained to those oocytes that were not distorted by the fixing process which was especially evident among the more developed stages. Where distortion occurred, 3 diameter measurements were made to provide an acceptable average diameter. Selection was also limited to oocytes displaying a nucleus with the assumption that it was situated towards an axis of the oocyte. Post ovulatory follicles could not be measured due to their convoluted shape.Oocyte development stages were classified following:Arocha F (2002) Oocyte development and maturity classification of swordfish from the north-western Atlantic. J Fish Biol 60: 13-27.Larval billfish sampling:A conical net of 1 mm mesh was hung from a 1 m diameter frame and towed clear of the wake from a stern quarter of a 6 meter boat at a nominal 2 knots for 30 minutes (approx. 1800 m). The frame was buoyed to position the net immediately below the sea surface.Larval billfish identification:All billfish larvae were identified by Jeff Leis of the Australian Museum based on head profile and pigmentation as applied in:Leis JM, Goldman G, Ueyanagi S (1987) Distribution and relative abundance of billfish larvae (Pisces: Istiophoridae) in the Great Barrier Reef lagoon and Coral Sea near Lizard Island, Australia. Fish Bull 85: 757-765.Six billfish larvae identified as black marlin by Leis were DNA tested and returned 3 black marlin, 2 blue marlin and 1 undetermined, thus invalidating the visual identification method.Chow S (1994) Identification of billfish species using mitochondrial cytochrome b gene fragment amplified by polymerase chain reaction. Report of the 2nd ICCAT billfish workshop. Int Comm Conserv Atl Tunas XLI:549-556.Larval billfish aging:Age/length relationships and growth models used to derive estimates for larval black marlin are described in:Prince ED, Lee DW, Zweifel JR (1991) Estimating age and growth of young Atlantic blue marlin Makaira nigricans from otolith microstructure. Fish Bull 89: 441-459.Serafy JE, Cowen RK, Paris CB, Capo TR, Luthy SA (2003) Evidence of blue marlin, Makaira nigricans, spawning in the vicinity of Exuma Sound, Bahamas. Mar Freshwater Res 54: 299-306.Sponaugle S, Denit KL, Luthy SA, Serafy JE, Cowen RK (2005) Growth variation in larval Makaira nigricans. J of Fish Bio 66: 822-835.PSAT tagging:Once a marlin was hooked and subsequently controlled alongside the vessel, the condition of the fish was assessed; condition factors that would eliminate an individual fish from the tagging study included visible bleeding from the mouth or gills, hook in the gut or throat, or exhaustion that prevented the fish from maintaining upright while swimming. Fish that were determined to be in good health were tagged using a hand-held tagging pole to insert a nylon dart into the dorsal musculature at the base of the tallest portion of the first dorsal fin. Tags were rigged with an umbrella-style dart and 136 kg test Sufix Superior monofilament (Yao I Fabric). The dart was inserted to a depth of 9.5 cm such that the nylon leader exited the body of the fish at a 45° angle towards the posterior of the fish.PSAT tags from both Wildlife Computers (WC-Redmond WA, USA) and Microwave Telemetry (MT-Columbia MD, USA) were used for this study. WC PSAT tag models included PAT0, PAT1, PAT2, PAT3, PAT5 and PAT6 and the original MT PTT-100 model. PSAT tags are intended to remain attached to the fish recording temperature, depth and light data until a preprogrammed date and time when an electrolytic release mechanism activates and causes the tag to detach from the fish. Once released, the tag floats to the surface and transmits data to the Argos satellite array. WC data are transmitted in a summarized histogram form while MT data are transmitted as raw hourly values for the measured parameters. The dispersal pattern of each WC tagged fish was estimated with an extended version of the TrackIt model. This model estimates two positions per day using raw light time-series data and is independent of the tag manufacturer's light-based positional estimates. MT PSATs do not provide raw light data so the TrackIt model cannot be employed and we relied upon the geolocation solutions from MT. Movement patterns were plotted on both a local and oceanbasin scale. For local movement analyses the GBR Environment (GBRE) was defined as the area encompassing the GBR, Queensland Plateau, Marion Plateau, Queensland and Townsville Troughs. This was done for two reasons - light based geolocation estimates were not precise enough to discriminate between fish locations adjacent to or 200 km seaward of the reef and, fishery data indicated that the GBRE experiences higher catch per unit effort during the months of October through December.PSAT tags are described in:Domeier ML, Kiefer D, Nasby-Lucas N, Wagschal A, O'Brien F (2005) Tracking Pacific bluefin tuna (Thunnus thynnus orientalis) in the northeastern Pacific with an automated algorithm that estimates latitude by matching sea surface temperature data from satellites with temperature data from tags on fish. Fish Bull 103: 292-306.The TrackIt model is described in:Nielsen A, Sibert JR (2007) State-space model for light-based tracking of marine animals. Can J Fish Aquat Sci 64: 1055-1068.Catch per unit effort data used to define the study area was sourced from:Williams D, McB, Milicich MJ, Kearney RE (1993) Trends in marlin abundance and stock composition off Eastern Australia as indexed by catch, effort and tagging data. Report to ECTUNAMAC. pp 81.Conventional tags:Industry and Investment New South Wales (I&I NSW), Australia, owns and maintains a conventional tagging database produced by the NSW Game Fish Tagging Program (GFTP). To gather migration data for select game fish species the GFTP has been distributing conventional tags to recreational fishers since 1973. A stainless steel anchor dart is used on larger species such as billfish and sharks. When compiling data for use in this study, tag recaptures that were missing location data or estimated size at both release and recapture were excluded. When analyzing movement of mature fish, recaptured fish that were a minimum of 100 kg upon release or recapture were included in the analyses. This was done to exclude all immature fish, based on the fact that females mature around 100 kg. Since males mature at a much smaller size (40 kg), certainly some mature males were unavoidably excluded from the analyses of mature fish movements.

Notes

Credit
Speare, Peter J, Mr (Co Investigator)

Credit
Domeier, Michael L (Co Investigator)