Nelson G.A.,Annisquam River Marine Fisheries Field Station
Transactions of the American Fisheries Society | Year: 2014
Cluster sampling is a common survey design used pervasively in fisheries research to sample fish populations, but it is not widely recognized by researchers. Because fish collected via cluster sampling are not independent of each other, standard simple random sampling estimators and statistical tests that assume independence cannot be used to make inferences about fish populations. If the clustered nature of fisheries data is ignored, the main consequence is that the type I error rate of common statistical tests will be severely inflated and significant differences will often be found in group comparisons where none exist. The goal of this paper is to provide an introduction to the estimation of population attributes and analysis of fisheries data collected via cluster sampling. This article addresses the nature of clustered fisheries data, reviews the random cluster sampling estimators of population attributes, explores the implications of violating the assumption of independence in hypothesis testing, and reviews current statistical approaches that can be used to analyze appropriately clustered data.Received November 8, 2013; accepted February 27, 2014. © 2014 © American Fisheries Society 2014.
Nelson G.A.,Annisquam River Marine Fisheries Field Station |
Armstrong M.P.,Annisquam River Marine Fisheries Field Station |
Stritzel-Thomson J.,Annisquam River Marine Fisheries Field Station |
Friedland K.D.,National Oceanic and Atmospheric Administration
Fisheries Oceanography | Year: 2010
Striped bass, Morone saxatilis, were captured and released with temperature-measuring data storage tags in Salem Sound, Massachusetts, to collect data on their thermal preferences in coastal and marine waters and to identify environmental factors that may influence temperatures experienced during their summer residence. Striped bass recaptured during summer of 2006 (21 of 151 releases) experienced a wide range of temperatures (6.5-28.0°C) while at-large for 1-53 days. Overall mean temperature and standard deviation selected by striped bass recaptured in Salem Sound during the longest commonly-shared duration of time (3-12 July) were 17.8 and 3.57°C, respectively. Comparison of temperature data between fish and 13 vertical arrays in Salem Sound revealed that striped bass experienced higher and more variable temperatures, and that daily changes in temperature actually experienced were unrelated to daily changes in surrounding ambient temperature. Regular cyclical changes in temperature of all striped bass and vertical arrays were identified as influences of the local tide, which contributed about a 2°C change in temperature, on average, over the complete cycle. Most striped bass appeared to limit their activities to depths shallower than the lower limit of the thermocline, above which temperatures generally exceed 9.0°C in Salem Sound. Therefore, it is likely that the vertical distribution of striped bass is restricted by the low temperatures below this depth. An implication of this finding is that the spatial distribution of striped bass may be defined coarsely by knowledge of the distribution of temperature in coastal areas. © 2010 Blackwell Publishing Ltd.
Hernandez K.M.,Integrated Statistics |
Hernandez K.M.,National Oceanic and Atmospheric Administration |
Hernandez K.M.,Moss Landing Marine Laboratories |
Risch D.,Integrated Statistics |
And 9 more authors.
ICES Journal of Marine Science | Year: 2013
Atlantic cod (Gadus morhua) stocks in northeastern US waters are depleted and stock recovery has been slow; research into the spawning behaviour of this species can help inform conservation and management measures. Male cod produce low-frequency grunts during courtship and spawning. Passive acoustic monitoring (PAM) offers a different perspective from which to investigate the occurrence, spatial extent and duration of spawning cod aggregations. A marine autonomous recording unit was deployed in the "Spring Cod Conservation Zone" (SCCZ) located in Massachusetts Bay, western Atlantic, to record cod grunts from April-June 2011. Cod grunts were present on 98.67% of the recording days (n = 75 days). They occurred across all 24 h, although significantly more grunts were found during the day than night-time (p = 0.0065). Grunt durations ranged from 57-360 ms, and the fundamental frequency and second harmonic had mean peak frequencies of 49.7 ± 5.6 and 102.9 Hz ± 10.9 sd, respectively. Cod grunt rates were low compared with those reported for other spawning fish, and may be indicative of diel movement patterns. Next steps will focus on expanding PAM coverage within the SCCZ, alongside prospecting for unknown spawning grounds within existing archival data. © 2013 © United States Government [NOAA] 2013. Published by Oxford University Press.