Catch and Effort from a Recreational Trolling Fishery in a Large Lake

Home , Trolling (fishing)

Catch and effort from a recreational trolling fishery in a large lake Catch and effort from Over the past several decades recreational fisheries have grown substantially throughout the world. Until recently, however, recreational catch has been a recreational trolling ignored in the management of many important fisheries. The studies presented in this thesis examine different approaches for monitoring recreational trolling fisheries’ catch and effort in Lake Vänern, Sweden, the largest lake in the European fishery in a large lake Union. Paper I presents results from a complemented roving/mail-in survey, designed to estimate recreational effort and catch of Atlantic salmon (Salmo salar) and brown trout (S. trutta). The results show that the recreational trolling fishery today harvests more salmon and trout annually than the commercial and subsistence fisheries combined, and that there are seasonal patterns in effort Anders Andersson and catch. Paper II evaluates different angler catch reporting methods (mail-in, tournament reports, and face-to-face interviews), compares catch rates within and among spring and fall fishing periods and examines mail-in data for recall bias. Harvest per boat day did not differ significantly among catch reporting methods, indicating that all three could be useful for estimating harvest rates. Finally, there was no evidence for recall bias in mail-in surveys. In summary, this thesis has developed the framework for a recreational angler survey program for Lake Vänern, and should be of interest to researchers and managers interested in estimating catch and effort for fisheries at large spatial scales.

ISBN 978-91-7063-706-3 Faculty of Health, Science and Technology

ISSN 1403-8099 Biology

LICENTIATE THESIS | Karlstad University Studies | 2016:28 LICENTIATE THESIS | Karlstad University Studies | 2016:28 Catch and effort from a recreational trolling fishery in a large lake

Anders Andersson

LICENTIATE THESIS | Karlstad University Studies | 2016:28 Catch and effort from a recreational trolling fishery in a large lake

Anders Andersson

LICENTIATE THESIS

Karlstad University Studies | 2016:28 urn:nbn:se:kau:diva-41780

ISSN 1403-8099

ISBN 978-91-7063-706-3

Distribution: Karlstad University Faculty of Health, Science and Technology Department of Environmental and Life Sciences SE-651 88 Karlstad, Sweden +46 54 700 10 00

Print: Universitetstryckeriet, Karlstad 2016

WWW.KAU.SE Abstract

Over recent decades recreational fisheries have grown substantially throughout the world. Despite this increase, catches from recreational fisheries have often been ignored in fisheries management, although this is now being remedied. Monitoring recreational fisheries can be expensive, and the primary means used for monitoring is angler (creel) surveys, typically funded from sales of fishing licences. The studies presented in this thesis examine different approaches for monitoring recreational trolling fisheries’ catch and effort, where fishing licenses are not required and there are no reporting requirements. I present results from a complemented roving/mail- in survey undertaken during 2013-2014 to estimate recreational effort and catch of Atlantic salmon (Salmo salar) and brown trout (S. trutta) in the largest lake in the European Union, Lake Vänern, Sweden. I also evaluate different angler catch reporting methods (mail-in, tournament reports and face-to-face interviews) and compare catch rates within and among spring and fall fishing periods. In addition, mail-in survey data are examined for recall bias.

I estimate that 28.7 tonnes of salmon and trout combined were harvested by the recreational trolling fishery in 2014, more than the commercial and subsistence fisheries combined. Seasonal differences in both recreational effort and catch were observed. Effort, in boat hours, was significantly higher in spring than in fall. Catch rates of trout were higher in fall than in spring, but there were no seasonal differences in catches of salmon. Harvest per boat day did not differ significantly among catch reporting methods, indicating that all three methods could be useful for managers interested in harvest rates. In contrast, total and released catch per boat day differed among reporting methods, with tournament anglers catching more fish in total. Finally, there was no evidence for recall bias in mail-in surveys, indicating that mail-in surveys are useful for collecting unbiased catch data. My study is the most comprehensive angler survey to date for Lake Vänern, and my results should be of immediate use to local fisheries managers and should also be of interest to researchers and managers interested in estimating catch and effort for fisheries at large spatial scales.

Contents

List of papers ...... 5 Contributions ...... 5 Introduction ...... 6 Objectives ...... 8 Material and methods ...... 9 Study site ...... 9 Angler survey methods ...... 10 Summary of results ...... 11 Discussion ...... 14 Acknowledgements ...... 17 References ...... 18

List of papers

This thesis is based on the following two papers, which are referred to by their Roman numerals.

I. Andersson, A., Greenberg, L., Bergman, E., Su, Z., Andersson, M., Piccolo, J. (2016). Estimating effort and catch of a recreational trolling fishery in one of Europe’s largest lakes. Manuscript. II. Andersson, A., Bergman, E., Greenberg, L., Piccolo, J. (2016). Comparing mail-in, interview and tournament catch rates for a recreational salmonid fishery. Manuscript.

Contributions

Anders Andersson had a leading role in the studies. John Piccolo, Larry Greenberg and Eva Bergman contributed to the main ideas, survey design, and writing. Anders Andersson performed the field work and collection of data. Furthermore, Anders ran the statistical tests and wrote both of the papers. In paper I, Zhenming Su provided advice on catch estimation and Magnus Andersson contributed with substantial knowledge about the Lake Vänern recreational fisheries, as well as made important comments for improving the paper. John Piccolo, Larry Greenberg and Eva Bergman made valuable comments for improving both of the papers.

Introduction

Fishing has been a major source of food for centuries and also an important recreational activity for decades in many countries (Valdimarsson & James 2001; Welcomme 2001). Since the mid-20th century, recreational fishing has increased substantially around the globe. In many coastal and inland areas this increase in activity has resulted in recreational fisheries that exceed commercial fisheries in terms of both catch and economic value (McPhee et al. 2002; Cooke et al. 2015). In the past, recreational fisheries have been considered to have negligible impacts on fish populations, and therefore recreational catch has often been ignored in fisheries management (McPhee et al. 2002; Post et al. 2002; Coleman et al. 2004). Today, awareness of the potential impact of recreational fisheries on fish populations has increased, and it is recognized that estimating recreational effort and catch is necessary for sustainable fisheries management (McPhee et al. 2002; Jones & Pollock 2012). Over the past decades, a substantial body of angler survey literature has been developed to accurate estimate catch and effort, although this still remains challenging.

In some recreational fisheries, reporting of catch is not mandatory, which can hinder monitoring and functional management (Hartill & Edwards 2015). In these fisheries, angler (or creel) surveys are the primary method of collecting effort and catch data, as well as other pertinent information about angler behavior (Pollock et al. 1994). Estimates of parameters such as effort, harvest and released catch provide information that can form the basis for management decisions such as size and bag limits and harvest allocation between commercial and recreational fisheries (Jones & Pollock 2012). There are two main types of angler surveys, on-site and off-site surveys, which in turn can each consist of different survey approaches. Examples of on-site surveys are access site, roving and aerial surveys, while mail, telephone, logbooks and diaries are examples of off-site surveys. An angler survey involving two or more contact methods is referred to as a complemented survey (Pollock et al. 1994). The approach one should use is determined by the

6 purpose of the study, survey area and budget limitations. Normally off- site surveys are less expensive than are on-site surveys (Pollock et al. 1994; Jones & Pollock 2012), but the main drawback is that off-site surveys are typically more susceptible to various biases (Pollock et al. 1994).

In general, there is no guarantee that anglers’ reports contain accurate data. Different survey techniques can be affected by various types of biases (Pollock et al. 1994). Some examples of biases that can occur in angler surveys are recall (memory) and nonresponse biases (Connelly et al. 2000), misidentification of species (Page et al. 2012), prestige bias and rounding bias (Pollock et al. 1994). Generally, self-reported catch, which is used for off-site techniques, seems to be more subject to bias than catch obtained from on-site surveys where creel clerks can inspect catch directly (Pollock et al. 1994; Roach et al. 1999). This is one reason why an access site survey is preferred for unbiased estimates of effort and catch.

The possibility of using an access-site survey, however, depends on budget resources and the scale of the study area (Pollock et al. 1994). In large lakes, reservoirs and coastal areas (e. g., large geographic areas), for example, there may be benefits of using off-site surveys. In addition to being less expensive to implement, they offer greater opportunities to get in contact with anglers when anglers are widely dispersed (Pollock et al. 1994; Henry & Lyle 2003; Jones & Pollock 2012). A compromise commonly used in large-scale studies to minimize bias while still reaching many anglers is to use some form of complemented survey, where catch is estimated from on-site and effort from off-site techniques (Jones & Pollock 2012).

Lake Vänern, Sweden, is the third largest lake in Europe and the largest lake in the European Union (EU), with major inland commercial, subsistence and recreational fisheries estimated at over 600 tonnes per year (Sandström et al. 2014). In addition to its large size, a major challenge for estimating recreational catch in Lake Vänern is that there are no reporting or license requirements for the recreational fisheries. As

7 a result, funding to support an angler survey program is lacking, and to date only a few sporadic surveys have been conducted. Consequently, previous estimates of annual harvest of Atlantic salmon (Salmo salar) and brown trout (S. trutta) are fraught with uncertainty and range from 16 to 88 tonnes (Johansson & Andersson 2011; Piccolo et al. 2012). This highlights the critical need for research directed at developing robust catch estimators for the Lake Vänern recreational fishery.

Objectives

The main objective of this thesis was to estimate fishing catch and effort for a salmon and trout recreational fishery in a large lake, Lake Vänern. In the first study (Paper I), my main objective was to estimate recreational trolling effort and catch of salmon and trout in the lake. This was done by developing a complemented survey approach that utilized the limited human and economic resources that were available. In addition, I examined seasonal patterns in effort and catch with focus on two main fishing periods, and I made the first species-specific catch estimates for salmon and trout in Lake Vänern. In Paper II, the main objective was to compare catch rates among different reporting methods (mail-in surveys, tournament reports and live face-to-face interviews) and between three survey periods. Furthermore, I also examined mail-in survey data for potential recall bias.

Material and methods

Study site

The study was conducted on Lake Vänern, the EUs’ largest lake, with a surface area of 5650 km2. Lake Vänern is an oligotrophic lake, with a mean depth of 27 meters (Nilsson 1979; Nyberg et al. 2001), and holds unique populations of landlocked Atlantic salmon and trout (Nilsson 1979; Ros 1981; Piccolo et al. 2012). Fishing for salmonids in Lake Vänern has been important for centuries (Degerman 2004), and in the early 1900s commercial fisheries harvested annually around 100 tonnes of salmon and trout combined (Nilsson 1979; Piccolo et al. 2012). Due to exploitation of tributaries and overfishing, catches in the lake declined dramatically, resulting in wild populations of less than 100 spawners in the mid-1900s (Piccolo et al. 2012). Today, substantial commercial, subsistence and recreational fisheries are maintained by compensatory hatchery stocking (Piccolo et al. 2012; Bergman et al. 2014). Since the 1990s wild populations are protected, and all wild salmon and trout must be released. However, fishing for hatchery salmonids in the lake is extensive, and in addition to the catches obtained by the recreational trolling fisheries, several sport trolling tournaments are conducted on the lake every year. Commercial and subsistence fisheries are required to report their catches, but this is not the case for recreational fisheries (Sandström et al. 2014). Hence, estimates of recreational, and therefore total catch, are very uncertain. Some of the most recent estimates of annual recreational harvest of salmon and trout are based upon fishing effort counts from 1998 and 2009, which are then multiplied by catch rates from two major trolling tournaments (Andersson et al. 2010; Johansson & Andersson 2011). Thus, there is a need to improve survey methods and estimates of total catch in Lake Vänern’s recreational fishery.

Angler survey methods

In Paper I, I performed a complemented roving/mail-in survey which included 1) effort counts of trailers and boats, and 2) distribution of mail-in surveys to anglers for collection of catch information. Effort counts were conducted at 20 major access sites (Fig. 1) in main fishing periods for salmon and trout (spring and fall 2014), and mail-in catch surveys were placed on the windshields of all cars with empty boat trailers in conjunction with effort counts. Mail-in surveys had pre-paid postage, and anglers could choose to report only one, or up to three fishing trips. Effort was estimated in boat hours per access site for survey periods by using an equation based upon a multiple day estimator for instantaneous counts (Lockwood et al. 1999). Catch was expressed as both total (includes both kept and caught and released fish) and harvested (kept) catch per boat hour for both salmon and trout, separately and together. Total harvest of salmon and trout combined was estimated for each period by multiplying total effort in boat hours with catch rates from survey periods estimated by The Ratio of Means Estimator (Lockwood et al. 1999), and then later also expanded to an annual harvest estimate.

20 . 1. 3 2. .

4 19 . Norway 18. 17 Sweden . .5 9 .6 Baltic Sea . .7 10.. 8 North Sea 13 16 . . . 11 15. .12 14. 10 km

Figure 1. Lake Vänern, Sweden, showing sampled access sites for the salmon recreational fishery, numbered in clockwise order.

Some literature argues that self-reported catch tends to be biased (Carline 1972; Roach et al. 1999). Therefore, I had a major interest in evaluating potential biases associated with the mail-in surveys. In Paper II, I compared three different reporting methods: mail-in surveys, tournament reports and live face-to-face interviews. I tested for catch rate differences for total, harvested and released catch per boat day among all methods and fishing periods. The first analysis (in Paper II) consisted of comparing mail-ins and tournament reports over three fishing periods. Mail-in surveys were distributed to anglers in the complemented survey in 2014 (as described in Paper I), but also during a pilot study in spring 2013, and tournament reports from all three fishing periods were obtained from the Swedish Anglers Association. The second analysis (in Paper II) consisted of comparing all three reporting methods over one period (fall 2014). In addition to mail-ins and tournament reports, face-to-face interviews were conducted during fall 2014 on weekend afternoons at six different access sites with high recreational trolling effort. For data analyses, a total number of 320 mail-in survey trips, 307 tournament reports and 58 face-to-face interviews were used. In addition to these two analyses, we also evaluated mail-in surveys for recall bias.

Summary of results

Major findings in Paper I were that recreational trolling fishing in Vänern is substantial and now harvests more salmon and trout annually (ca. 28.7 tonnes) than the commercial and subsistence fisheries combined (ca. 21 tonnes) (Fig. 2). Other findings were that recreational trolling effort differed between fishing periods, with significantly higher effort in boat hours in the spring than in the fall (Paper I; Tab. 1). Catch and harvest rates of salmon were significantly higher than catches of trout, independent of season. When comparisons within species were carried out, I found that catches of salmon did not differ between fishing periods, whereas both catch and harvest rates of trout were significantly higher in the fall than in the spring (Fig. 3).

In Paper II, my comparison of catch rates estimated by the different reporting methods showed no difference in terms of the number of harvested fish per boat day. Around one salmon or trout was harvested per boat day, independent of reporting method and fishing period (Fig. 4. see also Paper II; Fig. 1). In terms of released catch, tournament anglers reported significantly higher catch rates than those estimated from my mail-in survey (Fig. 4). Fishing periods showed significant differences for all estimates of catch rates (total, harvested and released). Total and released catch was higher in spring 2013 than in the other two periods, and harvest rates were lowest in spring 2014 (Paper II; Fig. 1). Finally, there was no indication that the mail-in surveys were affected by recall bias.

60 Recreational (previous surveys by Swedish Board of Fisheries) Recreational (Paper I)

) 50 Commercial

Subsistence tonnes

metric (

30 harvest

20 Annual 10

0 1995 2000 2005 2010 2015

Figure 2. Commercial and subsistence fisheries harvest of salmon and trout (data from the Swedish Agency for Marine and Water Management and the County Administrative Board of Värmland) compared to estimated recreational fishing harvest of salmon and trout for 1998, 2009 and 2014. White bars from 1998 and 2009 depict estimates made by the Swedish Board of Fisheries, and the hatched bar depicts estimates of the recreational fishery based upon the 2014 angler survey (Paper I).

a) Salmon catch b) Trout catch

)

hour

boat

per per fish

of c) Salmon harvest d) Trout harvest

(Nr. (Nr. CPUE

Figure 3. Boxplots showing catch and harvest rates for salmon and trout in the Lake Vänern recreational trolling fishery during spring and fall surveys 2014. Plots are based on completed fishing trips from mail-in surveys in spring (n=86) and fall (n=107).

a) total b) harvested c) released

day

boat Catch per per Catch

Interviews Mail-ins Tournaments Interviews Mail-ins Tournaments Interviews Mail-ins Tournaments

Figure 4. Catch per boat day from three different reporting methods, total, harvested and released catch during fall 2014. Number of fishing trips: 58 interviews, 142 mail- ins, and 33 tournaments.

Discussion

My research shows that the catch from the recreational fisheries in Lake Vänern is substantial, with catches of salmon and trout exceeding those in the commercial and subsistence fisheries. This result suggests that fisheries managers should continue to develop a robust angler survey program for Lake Vänern. One major challenge however, is the lack of funding for a monitoring program. For this reason, only two effort surveys have been conducted in the past, one in 1998 and one in 2009. These have been less extensive than the current study and have included only the spring fishing period (Andersson et al. 2010; Johansson & Andersson 2011).

I found seasonal variation in both effort and catch (Paper I; Paper II). Effort, when expressed in terms of the number of boat hours, was significantly higher in the spring than in the fall, which probably is related to the longer day length and hence longer fishing trips than in the fall, as there was no significant difference in the number of boat days. The fall season, in general, has more inclement weather (wind and rain), which may have also contributed to the lower fishing effort in fall. Catch also varied seasonally, but only for trout, with higher catch and harvest rates in the fall than in the spring (Paper I). This result gives further support to the notion that the fishery should be sampled in both spring and fall. Catches are expected to vary seasonally due to differences in fish behaviour in relation to temperature, dissolved oxygen and prey abundance and distribution. For many freshwater species, for example, catches often peak during spring and fall periods (Pope & Willis 1996).

An important result of this study is that the harvest rate of salmon and trout combined, which was approximately one per fishing trip, did not vary with reporting method (Paper II). Hence, any of the three reporting methods used in this study would be useful for managers who need information about harvest rates for the recreational trolling fisheries in Lake Vänern. In contrast, both total and released catch per boat day differed between reporting methods. Tournament anglers caught in

14 general more fish in total than others, highlighting the fact that tournament reports should be used with caution if estimating total or released catch (Paper II; see also Gabelhouse & Willis 1986).

The response rates in my mail-in survey were approximately 24 % for all three surveyed periods (Paper II), which can be considered quite good since no reminders could be sent out and no rewards could be offered; these tools are often used to increase response rates in mail surveys (Pollock et al. 1994). Response rates in other studies typically range from 7-54 % (Connelly et al. 2000; Roth et al. 2001; Connelly & Brown 2011; Melstrom & Lupi 2013; Zarauz et al. 2015), and may end up around 50 % even after three reminders (Pollock et al. 1994). Mail-in surveys with self-reported data have been shown to be subject to recall and prestige bias (Connelly et al. 2000; Jones & Pollock 2012), i. e., the risk that anglers forget over time or that submitted reports selectively show fishing trips with good catch rates. My analyses, however, showed that this was not the case, indicating that reporting bias among Lake Vänern recreational trolling fishers seems to be negligible, at least within the investigated time period (see Paper II).

As mentioned in the literature, catches of few, but memorable fish, usually are not forgotten (Pollock et al. 1994; see also McCormick et al. 2015); this may be the case for salmon and trout in Lake Vänern, where most anglers catch few, but large fish, and harvest is restricted to fish ≥ 60 cm. Mail-in surveys can therefore be considered as an unbiased method for catch estimates. Although reporting bias currently appears low, periodic assessments are important to monitor possible changes in reporting trends over time. In addition, other forms of voluntary reporting methods would be desirable to test, and currently the Swedish Anglers Association is developing web and phone-based applications. The integration of these into a robust angler survey program for Lake Vänern would appear essential, since there are no current plans to increase management funding or require fishing licenses. The major challenge with those new voluntary reporting methods is to get anglers to report. Moreover, effort surveys will continue to be a necessary complement to catch surveys.

Management of recreational fisheries at large spatial scales can be challenging. My research represents an attempt to compare different methods that can be used in developing a quantitative and robust angler survey program for a large lake, using Lake Vänern as a case study, and building upon earlier methods developed by the Swedish Board of Fisheries (Swedish Board of Fisheries 1998; Andersson et al. 2010). My results appear to be robust, with relatively low variances in estimates, but future research should further assess the method for biases in both effort and catch estimators. A better picture of fishing effort, both temporally (e.g. within and among years, during long spring days) and spatially (e.g., small ports) would be desirable. More visits at access sites, preferably two counts per port, would help to more accurately assess angler behaviour and see how fishing pressure can vary over a day. This could be done by selecting index ports that can be monitored more frequently to observe trends in the fishery and to collect additional angler behaviour data. One method of assessing the precision of our effort estimates could be to use aerial counts of fishing boats (e.g., Vølstad et al. 2006), but currently there is no funding available for such studies.

For Lake Vänern, the popular and ongoing fishery for hatchery salmon and trout, alongside slowly-recovering wild stocks, will pose challenging management questions in the future. Projections for recovery of wild stocks are on the order of several decades at a minimum (Bergman et al. 2015), so hatchery stocking will continue to be important for many years to come. One major challenge will be to optimize the number of hatchery smolts released, while taking wild fish into account, so that anglers can maintain or increase their catch of hatchery-released salmon and trout. To manage such a sustainable fishery, information about angler effort and catch is essential (McPhee et al. 2002; Post et al. 2002; Cooke et al. 2006). Together with studies of the impact of salmonids on prey abundance and the food web, we can increase our understanding of the entire life cycle for salmon and trout in this system, and thus improve conditions for hatchery smolt. An improved method for estimating catch and effort for salmon and trout in Lake Vänern should also provide a

16 framework for an angler survey program for other species as well, for which in terms of recreational fisheries, very little is known.

Acknowledgements

I would like to thank my supervisors for guiding me through this process. I would like to especially thank John Piccolo who inspired me and always encouraged me with positive thinking. For assistance in the field, I thank S. Jonsson, J. Wolfbrandt, D. Höök and R. Gow for their work as survey clerks. For information about the Lake Vänern trolling fishery I would like to thank M. Johansson, S-G. Steénson and E. Pettersen. Also thanks to colleagues at the Department of Environmental and Life Sciences and to J. Watz who helped me with statistical analyses. To Johanna, Tess and Leo: thank you for your love and for always supporting me. I couldn’t have made it without you.

References

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ISBN 978-91-7063-706-3 Faculty of Health, Science and Technology

ISSN 1403-8099 Biology

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