A video method for quantifying size distribution, density, and three-dimensional spatial structure of reef fish spawning aggregations

There is a clear need to develop fisheries independent methods to quantify individual sizes, density, and three dimensional characteristics of reef fish spawning aggregations for use in population assessments and to provide critical baseline data on reproductive life history of exploited populations. We designed, constructed, calibrated, and applied an underwater stereo-video system to estimate individual sizes and three dimensional (3D) positions of Nassau grouper (Epinephelus striatus) at a spawning aggregation site located on a reef promontory on the western edge of Little Cayman Island, Cayman Islands, BWI, on 23 January 2003. The system consists of two free-running camcorders mounted on a meter-long bar and supported by a SCUBA diver. Paired video “stills” were captured, and nose and tail of individual fish observed in the field of view of both cameras were digitized using image analysis software. Conversion of these two dimensional screen coordinates to 3D coordinates was achieved through a matrix inversion algorithm and calibration data. Our estimate of mean total length (58.5 cm, n = 29) was in close agreement with estimated lengths from a hydroacoustic survey and from direct measures of fish size using visual census techniques. We discovered a possible bias in length measures using the video method, most likely arising from some fish orientations that were not perpendicular with respect to the optical axis of the camera system. We observed 40 individuals occupying a volume of 33.3 m3, resulting in a concentration of 1.2 individuals m–3 with a mean (SD) nearest neighbor distance of 70.0 (29.7) cm. We promote the use of roving diver stereo-videography as a method to assess the size distribution, density, and 3D spatial structure of fish spawning aggregations.

A method for estimating the rate of shedding of tags from yellowfin tuna

ENGLISH: The present paper describes a new method for estimating the shedding rate of tags. The method utilizes not only data on tagging and recovery of fish marked with two tags but also data from those marked with one. One important advantage of the new technique is that the estimates of the shedding rates are free from distortion caused by variations in fishing intensity during the total recovery period. The idea of this method appears to be implicit in a short note by Gulland (1963). This technique has been applied to the data obtained by the Inter-American Tropical Tuna Commission in a tagging cruise off the west coast of southern Baja California, during June 1963, at which time both single and double-tagged yellowfin tuna were released. Details of the tagging procedure and equipment have been described by Fink (1965b). The results presented in the present paper are for yellowfin tuna tagged with dart tags. Estimates of shedding should be made separately for each species investigated and also for each type of tag used, since these rates may be variable and often unexpectedly high (Springer and McErlean 1961, Chadwick 1963). SPANISH: El presente estudio describe un nuevo método para estimar las tasas del desprendimiento de marcas. El método emplea no solamente los datos sobre la marcación y recobro de peces marcados con dos marcas, pero también datos de los peces marcados con una marca. Una ventaja importante de la nueva técnica, es que las estimaciones de las tasas de desprendimiento son libres de alteración, causada por las variaciones en la intensidad de pesca durante el período total de recobro. La idea de este método parece ser implícita en un breve apunte por Gulland (1963). Esta técnica se ha aplicado a los datos obtenidos por la Comisión Interamericana del Atún Tropical, en un crucero de marcación efectuado frente a la costa occidental al sur de Baja California, en junio de 1963, tiempo en el cual fueron liberados atunes aleta amarilla marcados tanto con una como con dos marcas. Los detalles del procedimiento de la marcación y del equipo usado han sido descritos por Fink (1965b). Los resultados presentados en este estudio, pertenecen al atún aleta amarilla marcado con marcas de dardo. Las estimaciones del desprendimiento deben efectuarse separadamente para cada especie que ha sido investigada y también para cada tipo de marca usado, ya que estas tasas pueden ser vaiables, y a menudo inesperadamente altas (Springer y McErlean 1961, Chadwick 1963). (PDF contains 20 pages.)

An egg production method for estimating spawning biomass of pelagic fish: Application to the northern anchovy, Engraulis mordax

Fishery scientists engaged in estimating the size of free-swimming populations have never had a technique available to them whereby all the parameters could be estimated from a resource survey and where no parameter values need to be assumed. Recognizing the need for a technique of this kind, the staff of the Coastal Fisheries Resources Division of the Southwest Fisheries Center (SWFC) devised an egg production method for anchovy biomass assessment. Previously, anchovy biomass was estimated by approximate methods derived from a long-time series and anchovy larval abundance, which required about 5 ma of shiptime each year to integrate the area under a seasonal spawning curve. One major assumption used in the larval abundance census method is that there is constant proportionality between larval numbers and spawning biomass. This has now proved to be erroneous. (PDF file contains 105 pages.)

A rapid and simple method for the determination of Formaldehyde in Fishery Products

The content of free formaldehyde (FA) in minced fish muscle was measured by the following procedure: A mixture of minced fish muscle and water was deproteinized by means of the Carrez reagent. The FA content of the filtrate was determined reflectometrically using the Reflectoquant test strips and the RQflex. The results agreed well with the colorimetrically (Nash test) measured FA content. Der Gehalt an freiem Formaldehyd (FA)in Fischerzeugnissen wurde mit folgender Methode bestimmt: Zerkleinertes Fischfleisch wurde mit Wasser homogenisiert und mit Carrez-Reagenz enteiweißt. Der Formaldehydgehalt des Filtrates wurde reflektometrisch unter Verwendung von Reflectoquant-Teststätbchen und des RQflex ermittelt. Die Ergebnisse stimmten gut mit kolorimetrisch (Nash Test) gemessenen FA-Gehalten überein.

Major and trace element analytical methods of the National Status and Trends Program: 2000-2006

This document contains analytical methods that detail the procedures for determining major and trace element concentrations in bivalve tissue and sediment samples collected as part of the National Status and Trends Program (NS&T) for the years 2000-2006. Previously published NOAA Technical Memoranda NOS ORCA 71 and 130 (Lauenstein and Cantillo, 1993; Lauenstein and Cantillo, 1998) detail trace element analyses for the years 1984-1992 and 1993-1996, respectively, and include ancillary, histopathology, and contaminant (organic and trace element) analytical methods. The methods presented in this document for trace element analysis were utilized by the NS&T Mussel Watch and Bioeffects Projects. The Mussel Watch Project has been monitoring contaminants in bivalves and sediment for over 20 years, and is the longest active contaminant monitoring program operating in U.S. costal waters. Approximately 280 Mussel Watch sites are monitored on biennial and decadal timescales using bivalve tissue and sediment, respectively. The Bioeffects Project applies the sediment quality approach, which uses sediment contamination measurements, toxicity tests and benthic macroinfauna quantification to characterize pollution in selected estuaries and coastal embayments. Contaminant assessment is a core function of both projects. Although only one contract laboratory was used by the NS&T Program during the specified time period, several analytical methods and instruments were employed. The specific analytical method, including instrumentation and detection limit, is noted for each measurement taken and can be found at http://NSandT.noaa.gov. The major and trace elements measured by the NS&T Program include: Al, Si, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Sn, Sb, Ag, Cd, Hg, Tl and Pb.