This article was downloaded by: [Department Of Fisheries] On: 28 February 2013, At: 22:44 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK North American Journal of Fisheries Management Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/ujfm20 The Influence of Release Strategy and Migration History on Capture Rate of Oncorhynchus mykiss in a Rotary Screw Trap Ian A. Tattam a d , James R. Ruzycki b , Peter B. Bayley c , Hiram W. Li a & Guillermo R. Giannico c a Oregon Cooperative Fishery Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon, 97331, USA b Oregon Department of Fish and Wildlife, Eastern Oregon University, 203 Badgley Hall, One University Boulevard, LaGrande, Oregon, 97850, USA c Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon, 97331, USA d Oregon Department of Fish and Wildlife, Post Office Box 9, John Day, Oregon, Oregon, 97845, USA Version of record first published: 19 Feb 2013. To cite this article: Ian A. Tattam , James R. Ruzycki , Peter B. Bayley , Hiram W. Li & Guillermo R. Giannico (2013): The Influence of Release Strategy and Migration History on Capture Rate of Oncorhynchus mykiss in a Rotary Screw Trap, North American Journal of Fisheries Management, 33:2, 237-244 To link to this article: http://dx.doi.org/10.1080/02755947.2012.758202 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. North American Journal of Fisheries Management 33:237–244, 2013 C American Fisheries Society 2013 ISSN: 0275-5947 print / 1548-8675 online DOI: 10.1080/02755947.2012.758202 ARTICLE The Influence of Release Strategy and Migration History on Capture Rate of Oncorhynchus mykiss in a Rotary Screw Trap Ian A. Tattam*1 Oregon Cooperative Fishery Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331, USA James R. Ruzycki Oregon Department of Fish and Wildlife, Eastern Oregon University, 203 Badgley Hall, One University Boulevard, LaGrande, Oregon 97850, USA Peter B. Bayley Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331, USA Hiram W. Li Oregon Cooperative Fishery Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331, USA Guillermo R. Giannico Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331, USA Abstract Rotary screw traps are used in rivers throughout the west coast of North America to capture emigrating juvenile salmonids. Calibrating the capture efficiency of each trap is essential for valid estimates of fish passage. We released PIT-tagged Oncorhynchus mykiss upstream of a rotary screw trap in the South Fork John Day River, Oregon, to estimate capture efficiency. We used three strategies for release of fish recently captured in the trap. We recaptured 28% of medium-sized fish (86–145 mm FL) and 14% of large-sized fish (146–230 mm FL) released during daylight 1.6 km upstream from the trap. We recaptured 33% of medium-sized fish and 17% of large-sized fish released Downloaded by [Department Of Fisheries] at 22:44 28 February 2013 during daylight 4.8 km upstream from the trap. We recaptured 42% of medium-sized fish and 23% of large-sized fish released at twilight 1.8 km upstream from the trap. A PIT tag antenna detected summer-tagged parr (which were PIT-tagged upstream 1–5 months before migration) as they approached the trap to evaluate potential bias from reduced recapture of recently trapped fish. We captured 53% of the medium-sized first-time migrants and 40% of the large-sized first-time migrants. Although average capture efficiencies of first-time migrants were greater than those from any of the recently trapped fish from the three release strategies, twilight releases of recently trapped fish were the least negatively biased, especially for medium-sized fish. Extensive population monitoring of salmonid fishes across et al. 1991). Returns of adult anadromous salmonids are in- the west coast of North America (Volkhardtet al. 2007) has been fluenced by numerous factors in freshwater and marine life initiated in response to declining salmonid abundance (Nehlsen stages. Survival rates in migratory corridors and in the ocean are *Corresponding author: [email protected] 1Present address: Oregon Department of Fish and Wildlife, Post Office Box 9, John Day, Oregon 97845, USA. Received May 7, 2012; accepted December 6, 2012 237 238 TATTAM ET AL. variable (Bilton et al. 1982; Achord et al. 2007) and may mask movement patterns. There has been no evaluation of whether the influence of freshwater rearing areas on production. Hence, these protocols result in equal capture efficiency between recent there is a need to determine abundance by life stage (Solazzi releases and migrants that have not been previously captured et al. 2000; Johnson et al. 2005) to measure effects of proximate in an RST. We evaluated these protocols by estimating capture factors, such as marine survival (Pyper et al. 2002). Most of- efficiency for Oncorhynchus mykiss that were PIT-tagged 1–5 ten such life history monitoring involves estimation of numbers months before their downstream migration (hereafter “summer- of (1) out-migrant juveniles emigrating from freshwater, and tagged parr”) and monitored by a PIT tag antenna immediately (2) adults returning to freshwater to spawn. upstream from an RST. Abundance estimates of juvenile salmonids emigrating from The three objectives of this study were: (1) compare esti- rearing habitats require out-migrant traps, except in the few mates of the capture efficiency of an RST among recent releases situations where census counts may be conducted at weirs. A made during daylight hours in two different locations and recent common out-migrant trap throughout the west coast of North releases made after the end of civil twilight, (2) develop a size- America is the rotary screw trap (RST; E.G. Solutions, Corvallis, structured model predicting capture efficiency for juvenile O. Oregon). Rotary screw caps can be nested inside weirs (Scace mykiss, and (3) validate the accuracy of the model by compar- et al. 2007) to increase capture efficiency. This can potentially ing the model-predicted capture efficiency for recent releases result in overcrowding of the holding box, causing mortality against estimates of capture efficiency for summer-tagged parr of biologically and economically valuable fishes (Music et al. detected by an antenna as they approached an RST. 2010). Thus, RSTs are commonly used as a “stand-alone” gear that samples a portion of the channel profile and captures a portion of the emigrant population. Valid estimates of capture METHODS efficiency are required for each RST in each location (Thedinga Site description.—This study was conducted in the South et al. 1994; Roper and Scarnecchia 2000) in order to estimate Fork John Day River (SFJD), a fifth-order basin located in out-migrant abundance. northeastern Oregon (Figure 1). The SFJD supports a natu- Capture efficiency varies depending on stream size, water rally reproducing population of O. mykiss, including resident velocity, water depth, cone rotation speed, and fish size (Roper and anadromous life history types. No hatchery stocking occurs and Scarnecchia 2000). The most commonly used method of in this basin, so all O. mykiss observed in this study were natu- estimating capture efficiency is to capture unmarked fish in the rally produced. Oncorhynchus mykiss are widely distributed in trap, apply a unique mark or tag, such as a PIT tag (Schultz et al. the SFJD and its four main tributaries downstream from Izee 2006; Copeland and Venditti 2009), and release the marked fish Falls, a barrier for anadromous fish movement (Figure 1). Em- upstream of the RST. The proportion of these marked fish (here- igration of juvenile O. mykiss from the SFJD is bimodal, with after referred to as “recent releases”) subsequently recaptured peaks occurring in October–November and April–May. During in the trap estimates capture efficiency for that sample period fall 2005, we estimated that 3,966 O. mykiss migrated past this (Thedinga et al. 1994; Miller et al. 2000). This mark–recapture RST site (I. Tattam, unpublished data). The O. mykiss captured population estimation technique is subject to the assumptions in the trap during this period ranged in fork length (FL) from 82 of the Petersen estimate (Seber 1982). Violation of any of these to 227 mm, with a mean of 140 mm. assumptions can result in erroneous population estimates (Frith We operated a 1.52-m-diameter RST at river kilometer 10 of et al. 1995). The most pertinent, yet seldom evaluated, is the as- the SFJD (Figure 1). An RST comprises a partially submerged sumption of equal capture efficiency of marked and unmarked cone with an interior helical structure that is passively rotated fish. For an estimate of catch efficiency to be unbiased the cap- by water pressure and funnels emigrant fish into a submerged Downloaded by [Department Of Fisheries] at 22:44 28 February 2013 ture efficiency of recent releases, which are fish captured in an holding box on the downstream end of the trap.