Estimating Harvest of Anglers on Large Geographic Scale Using a Combined Telephone-Diary Survey Approach: Strength, Limitations and Some Findings

Fisheries managers are looking for valid information on basic characteristics of recreational fisheries, such as landings and effort data, to inform management decisions. A complementary survey approach was designed to generate data on effort and harvest as well as various human dimensions of anglers using a telephone-diary-mail-survey design for a multi-species, multi-site fishery in a water-rich state in northern Germany (Mecklenburg-Vorpommern). First, a nationwide telephone screening was applied to estimate the total number of active resident and non-resident anglers in the study area. Afterwards, a one year diary study with randomly recruited resident and non-resident anglers was conducted. Beside the documentation of date, effort and harvest the diary participants were also asked to recorded additional information as directed effort, used angling method and satisfaction with the harvest. Routine check-up telephone calls were used to encourage the participants, generate detailed human dimensions data on the characteristics of anglers and evaluate diary entries. After the end of the diary study, 648 anglers (response rate 58%) returned complete diaries. Responding diarists were significantly older, had a higher level of education and encompassed more avid anglers than the non-responding participants. Thus, resident diarists were weighted against external characteristics of a random sample of the resident angler population to reduce the risk of biased catch and harvest estimates. Indeed, estimates for harvest and effort based on weighted samples were significantly lower than unweighted mean estimates. Extrapolations of average annual harvest rates per angler to the population level revealed that for the most economically important fish species such as eel (Anguilla anguilla), cod (Gadus morhua), pike (Esox lucius), carp (Cyprinus carpio) or perch (Perca fluviatilits), recreational fishing landings greatly exceeded commercial fisheries landings. Because diary estimates of annual angler landings were generally smaller relative to estimates of angler harvest stemming from three-month recall periods using telephone surveys and control on-site creel surveys, we concluded that the use of diary-data likely resulted in conservative estimates of total landings. Our survey design may serve as a model for further studies because of its cost-effectiveness relative to standard creel surveys and because the panel structure of diary studies allows rich insights into individual angler behaviour that is not possible to be accomplished by cross-sectional creel surveys.