Accuracy of Trip Durations Reported by Marine Sport-Boat Fishermen

Self‐reporting bias in sport fisheries of Chinook Salmon Oncorhynchus tshawytscha in Idaho was quantified by comparing observed and angler‐reported data. A total of 164 observed anglers fished for 541 h and caught 74 Chinook Salmon. Fifty‐eight fish were harvested and 16 were released. Anglers reported fishing for 604 h, an overestimate of 63 h. Anglers reported catching 66 fish; four less harvested and four less released fish were reported than observed. A Monte Carlo simulation revealed that when angler‐reported data were used, total catch was underestimated by 14–15 fish (19–20%) using the ratio‐of‐means estimator to calculate mean catch rate. Negative bias was reduced to six fish (8%) when the means‐of‐ratio estimator was used. Multiple linear regression models to predict reporting bias in time fished had poor predictive value. However, actual time fished and a categorical covariate indicating whether the angler fished continuously during their fishing trip were two variables that were present in all of the top a priori models evaluated. Underreporting of catch and overreporting of time fished by anglers present challenges when managing Chinook Salmon sport fisheries. However, confidence intervals were near target levels and using more liberal definitions of angling when estimating effort in creel surveys may decrease sensitivity to bias in angler‐reported data. Received January 3, 2013; accepted May 20, 2013

Section: Modelsupporting

confidence: 70%

Section: Modelmentioning

confidence: 99%

Self‐Reporting Bias in Chinook Salmon Sport Fisheries in Idaho: Implications for Roving Creel Surveys

McCormick

Quist

Schill

2013

“…In contrast, Johnson and Wroblewski (1962), who instructed their survey clerks to round their observed trip lengths to the nearest quarter hour, found no significant difference between the observed and reported estimates of trip duration. Similarly, McEachron et al (1986) compared anglergenerated estimates (rounded to 0.5 h) to observed trip durations (rounded to 0.1 h) and found no significant difference between them.…”

Section: Discussionmentioning

confidence: 99%

“…The accuracy of angler-generated estimates of trip duration has been examined in some recreational fisheries (Johnson and Wroblewski 1962;Edwards 1971;Radford 1973;McEachron et al 1986;Phippen and Bergersen 1991). These studies have shown inconsistent trends: some find that anglers tend to overestimate the duration of their fishing trip (Edwards 1971), others that they tend to underestimate it (Phippen and Bergersen 1991), and still others find that angler-generated estimates of trip duration are unbiased (Johnson and Wroblewski 1962;Radford 1973;McEachron et al 1986).…”

mentioning

confidence: 99%

“…These studies have shown inconsistent trends: some find that anglers tend to overestimate the duration of their fishing trip (Edwards 1971), others that they tend to underestimate it (Phippen and Bergersen 1991), and still others find that angler-generated estimates of trip duration are unbiased (Johnson and Wroblewski 1962;Radford 1973;McEachron et al 1986). The variable outcomes of these previous studies indicate that it is prudent to test the accuracy of angler-generated estimates of trip duration for different fisheries.…”

mentioning

confidence: 99%

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The Importance of Validating the Duration of Fishing Trips: Are Harvest Rates from On‐Site Recreational Fishing Surveys Unbiased?

Steffe¹,

Murphy²

2010

Harvest rates are often used as indicators of fishing quality and in the estimation of total harvest in some on‐site survey designs. The unbiased estimation of harvest and fishing effort is critical for calculating accurate harvest rates. On‐site survey designs allow survey clerks to validate harvest data directly. This harvest validation assumes that the level of intentional deception by fishers is relatively small. Therefore, validating angler‐generated estimates of trip duration is important because this can provide evidence that harvest rates and other variables derived from effort data are also unbiased. Also, one can partition effort and harvest within trips to calculate directed harvest rates for different target species or species groups, knowing that the angler‐generated estimates of total trip length are not contributing systematically to any bias in the directed harvest rates. We examined the accuracy of trip duration estimates reported by trailer boat fishers in the marine waters of New South Wales, Australia. Comparing these angler‐generated estimates with observed records of actual trip duration demonstrated that the angler‐generated estimates were empirically unbiased both for estimates in terms of party‐hours and those in terms of angler‐hours. These findings have several implications for the interpretation and analysis of survey results. We therefore recommend that angler‐generated estimates of trip duration be validated for different recreational fisheries; moreover, reliable reference points should be incorporated into all interview protocols because they can minimize the bias in self‐reported estimates of fishing effort. The validation of trip duration and harvest rate data are vital for convincing fisheries managers and stakeholders that surveys can provide reliable information about a fishery.

Accuracy of Angler‐Reported Harvest in Roving Creel Surveys

Mallison

Cichra

2004

Harvest data obtained during roving creel surveys are often based on angler‐reported information without validation. Angler creels were inspected following interviews during roving creel surveys on three Florida lakes. Comparisons between reported and counted harvest revealed significant differences for anglers targeting sunfish Lepomis spp. (22% error) and black crappie Pomoxis nigromaculatus (7% error). Differences were negligible for anglers targeting sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis), palmetto bass (male white bass × female striped bass), and largemouth bass Micropterus salmoides. Accuracy among species was inversely related to bag limit size; this was attributed to a combination of factors, including species, number and size of fish harvested, limit‐conscious behavior of anglers, and differences among angler groups. Accuracy within species was not significantly influenced by the reported number of fish harvested or trip duration, nor was the interaction of the two significant. Daily total harvest estimates based on reported data were biased for sunfish (19% error) and black crappies (5% error), but correction factors were effective in reducing total errors to 2% for both species. Inspection of creels is recommended for all roving creel survey interviews when accuracy is critical to meeting study objectives. When moderate accuracy is sufficient, angler‐reported harvest may be used if validated or adjusted with a correction factor if found to be inaccurate.