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Sampling Statistics in the Atlantic Menhaden Fishery

Author: Alexander J. Chester

Publisher:

Published: 1984

Total Pages: 478

ISBN-13:

Atlantic menhaden, Brevootia tyrannus, the object of a major purse-seine fishery along the U.S. east coast, are landed at plants from northern Florida to central Maine. The National Marine Fisheries Service has sampled these landings since 1955 for length, weight, and age. Together with records of landings at each plant, the samples are used to estimate numbers of fish landed at each age. This report analyzes the sampling design in terms of probability sampling theory. The design is classified as two-stage cluster sampling, the first stage consisting of purse-seine sets randomly selected from the population of all sets landed, and the second state consisting of fish randomly selected from each sample set. Implicit assumptions of this design are discussed with special attention to current sampling procedures. Methods are developed for estimating mean fish weight, numbers of fish landed, and age composition of the catch, with approximate 95% confidence intervals. Based on specific results from three ports (Port Monmouth, N.J., Reedville, Va., and Beaufort, N.C.) for the 1979 fishing season, recommendations are made for improving sampling procedures to comply more exactly with assumptions of the sampling design. These recommendations include adopting more formal methods for randomizing set and fish selection, increasing the number of sets sampled, considering the bias introduced by unequal set sizes, and developing methods to optimize the use of funds and personnel.

Age and Size Composition of the Menhaden Catch Along the Atlantic Coast of the United States, 1952-55

Author: Fred C. June

Publisher:

Published: 1959

Total Pages: 76

ISBN-13:

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Included are a brief description of menhaden purse-seine fishing gear, methods, and seasons; a summary of the major features of the 1955 Atlantic Coast purse-seine fishery; a description and analysis of the methods of sampling the catches; and tabular data resulting from the catch-sampling program. Measurements of the catch of Atlantic menhaden (Brevoortia tyrannus), apparent abundance, and total fishing effort showed considerable variation in different areas of the coast in 1955, with highest apparent abundance encountered on the North Carolina fall fishing grounds. Age, length, and weight composition of samples from the catches from 1952 through 1955 revealed the presences of a dominant year class in the fishery and established that different age and size groups support the catches in different areas along the coast; in summer, younger, smaller fish were found to occur in southern waters, and older, larger fish, farther northward. All age and size groupings were shown to be represented in the fall fishery off North Carolina.