The use of aerial photographs for estimating school sizes of cetaceans

Scott, Michael D. and Perryman, Wayne L. and Clark, William G. (1985) The use of aerial photographs for estimating school sizes of cetaceans. Inter-American Tropical Tuna Commission Bulletin, 18(5), pp. 381-419.

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Abstract

ENGLISH: The accuracy and precision of dolphin school size estimates based on aerial photograph counts were examined using data collected on recent aerial and ship surveys. These estimates were found to be accurate during a 1979research cruise aboard a tuna purse-seiner; dolphin schools were photographed from the ship’s helicopter, encircled with the purse-seine, and then counted as the dolphins were released from the net. A comparison of photographic estimates with these counts indicated that the relationship was fairly close and gave no indication of significantly differing from 1:1. During a 1980 aerial study, photographic estimates from different schools, passes, and camera formats were compared and were found to be quite precise with a standard deviation of approximately 60/0 of school size. Photographic estimates were also compared with estimates made by aerial observers. Most observers tended to underestimate school size, particularly for large schools. The variability among observers was high, indicating that observers should be individually calibrated. SPANISH: Se examinó la exactitud y la precisión de las estimaciones de la magnitud de los cardúmenes de delfines basadas en el cálculo de las fotografías aéreas, usando los datos obtenidos en los últimos reconocimientos aéreos y de los barcos. En 1979, durante un crucero de investigación en un cerquero atunero, se encontró que estas estimaciones eran acertadas; se fotografiaron los cardúmenes de delfines desde un helicóptero del barco, cercados con la red y luego se contaron a medida que se libraban los delfines de la red. Una comparación de las estimaciones fotográficas con estos cálculos indicó que la relación era bastante aproximada y no hubo indicación que se diferenció significativamente de la razón 1:1. Durante un estudio aéreo en 1980, se compararon las estimaciones fotográficas de diferentes del cardúmenes, en los pases y los formatos de las cámaras y se encontró que eran bastante precisos, con una desviación normal de cerca del 60/0 de la magnitud cardumen. Se compararon también las estimaciones fotográficas con las estimaciones realizadas por los observadores aéreos. La mayoría de los observadores tienden a subestimar la magnitud de los cardúmenes, especialmente los cardúmenes grandes. La variabilidad entre los observadores fue elevada, lo que indica que se deben calibrar individualmente los datos de observadores. (PDF contains 39 pages.)

Item Type: Article
Title: The use of aerial photographs for estimating school sizes of cetaceans
Personal Creator/Author:
CreatorsEmail
Scott, Michael D.
Perryman, Wayne L.
Clark, William G.
Journal or Publication Title: Inter-American Tropical Tuna Commission Bulletin
Volume: 18
Number: 5
Page Range: pp. 381-419
Date: 1985
Issuing Agency: Inter-American Tropical Tuna Commission
Additional Information: This article is bilingual and contains both Spanish and English translations.
Uncontrolled Keywords: aerial photography; school size; cetacean; fotografias aereas; los cardúmenes; los cetaceos
Subjects: Management
Oceanography
Item ID: 3459
Depositing User: Joan Parker
Date Deposited: 28 May 2010 19:13
Last Modified: 29 Sep 2011 17:26
URI: http://aquaticcommons.org/id/eprint/3459

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