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Larval Fish Identification from Cruises at the Hancock Seamounts, TC-84-05 and TC-85-01

Metadata Updated: October 19, 2024

Ichthyoplankton sampling was conducted aboard the NOAA vessel Townsend Cromwell in 9-29 July 1984 and 4-10 February 1985. Collectors included George Boehlert, James Uchiyama, Robert Humphreys, Randolph Chang, Alan Everson, Victor Honda, Bert Kikkawa, Raymond Clarke, Thomas Kazama, and Michael Seki. Two locations were sampled intensively during these cruises; one location was over the seamount summit ("seamount" location); the other location was 20 km west, over a water depth of approximately 1,800-4,750 m ("reference" location). Ichthyoplankton was sampled with an opening-closing Tucker trawl equipped with three nets and a double-release mechanism operated by messengers. The nets were 0.333 mm mesh (Nitex) with a 1.4 m2 mouth area. Ship speed was adjusted over tow speeds of about 0.9-1.1 m/second to maintain a wire angle at 45?. At this angle, the effective mouth area of the Tucker trawl is 1.0 m2 ; tow depths were estimated as a function of wire angle and meters of wire out. Four discrete depth strata (0-25, 25-50, 50-100, and 100-200 m) were sampled. Replicate tows at each depth comprised a sampling series. To sample at discrete depths without contamination by animals from shallower depths, the trawl was lowered with the first net open, and the second net was opened for the desired sampling time and then closed, and the trawl was retrieved with the third net open. To sample the two shallower strata, the trawl was lowered to 50 m, the second net was opened at that depth, and then the third net was opened at 25 m to sample the shallow stratum. For the two deeper strata, the second net was closed at the upper end of each stratum, and the trawl was retrieved with the third net open. Thus, a full set of duplicate samples for each depth stratum required six deployments of the trawl. The summer cruise had two series of night sampling (9-10 and 28-29 July) and one of day sampling (14-15 July); the winter cruise had one series of day and night sampling (4-10 February 1985). Each net was fished for 18 minutes and tows were conducted in a stepped oblique fashion, in an attempt to sample depths equally within each stratum. The volume of water filtered was estimated with calibrated General Oceanics flowmeters mounted in the center of each net. Plankton samples were preserved at sea in a 4% buffered formaldehyde seawater mixture. In the laboratory, plankton volume was determined from a known total volume minus the remaining water volume after the plankton were strained (Omori and Ikeda 1984); gelatinous plankton and fishes larger than approximately 50 mm were removed before the volume was determined. Whole samples were sorted for fish eggs, larvae, and squid para larvae under a dissecting microscope. Larval fishes were identified to the lowest possible taxonomic level by Bruce Mundy.

Access & Use Information

License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Dates

Metadata Date February 29, 2024
Metadata Created Date October 19, 2024
Metadata Updated Date October 19, 2024
Reference Date(s) May 5, 1992 (publication)
Frequency Of Update notPlanned

Metadata Source

Harvested from NMFS PIFSC

Additional Metadata

Resource Type Dataset
Metadata Date February 29, 2024
Metadata Created Date October 19, 2024
Metadata Updated Date October 19, 2024
Reference Date(s) May 5, 1992 (publication)
Responsible Party (Point of Contact)
Contact Email
Guid gov.noaa.nmfs.inport:8792
Access Constraints Cite As: Pacific Islands Fisheries Science Center, [Date of Access]: Larval Fish Identification from Cruises at the Hancock Seamounts, TC-84-05 and TC-85-01 [Data Date Range], https://www.fisheries.noaa.gov/inport/item/8792., Access Constraints: None
Bbox East Long 180
Bbox North Lat 31
Bbox South Lat 29
Bbox West Long 178
Coupled Resource
Frequency Of Update notPlanned
Harvest Object Id 91e458b4-2384-4c92-8f97-d0c87180e105
Harvest Source Id c0beac72-5f43-4455-8c33-1b345fbc2dfe
Harvest Source Title NMFS PIFSC
Licence NOAA provides no warranty, nor accepts any liability occurring from any incomplete, incorrect, or misleading data, or from any incorrect, incomplete, or misleading use of the data. It is the responsibility of the user to determine whether or not the data is suitable for the intended purpose.
Lineage Data was collected in the field by PIFSC staff, and entered in table format into electronic spreadsheets.
Metadata Language eng
Metadata Type geospatial
Old Spatial {"type": "Polygon", "coordinates": [[[178.0, 29.0], [180.0, 29.0], [180.0, 31.0], [178.0, 31.0], [178.0, 29.0]]]}
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True
Temporal Extent Begin 1984-07-09
Temporal Extent End 1984-07-29

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