Note:  The following article was written in 1998 by Maryland DNR Fisheries Biologist Rudy Lukacovic.  He condensed the paper in March 2011 for Careful Catch readers.  The regulations cited were those in effect during the time of the original publication and are not current.  For current fishing regulations visit the Maryland DNR fishing regulations website.

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Recreational Catch-and-Release Mortality of White Perch
Prepared by Rudolph Lukacovic
(1998)

INTRODUCTION

Management of recreationally important fish involves the use of tools such as minimum size restrictions, creel limits and/or closed seasons. Currently white perch Morone americana  caught by recreational fishermen in Maryland are not protected or regulated by any of these management options.
White perch was the primary species targeted by recreational anglers in spring in the Choptank and Chester Rivers in 1996 and 1997 (Sadzinski and Webb 1998). White perch accounted for 85% of the four most commonly caught and released species (white perch, yellow perch Perca flavescens, channel catfish Ictalurus punctatus and white catfish Ictalurus catus). The general fishing experience for white perch on the Choptank was ranked the highest by anglers among the four targeted species, however 57% of those anglers interviewed ranked the fishing as only fair or poor. Twenty five percent of the white perch caught from the Choptank River in 1996 were harvested and represented 91% of the overall harvested catch. Anglers that targeted white perch in 1996 ranked the fishing as poor (30%), fair (27%), good (37%) or excellent (6%).
In the future it is possible that a minimum size restriction or creel limit for recreational fishing might be considered as a means of manipulating the size structure of the population. White perch less than 8 in were harvested at rates well below their proportion in the population because anglers generally prefer fish over 8 inches.
Minimum size limits are used to protect and enhance fish populations by allowing fish to live long enough for them to spawn one or more times. It is also an effective way to provide quality fishing by preventing the harvest of smaller individuals and allowing a greater number fish to survive to a more desirable size. Creel limits reduce fishing mortality if they are less than typical angler catch. Minimum size limits and creel limits will work if survival rate of the released fish is high.
White perch are among the three most sought-after recreational species in Maryland’s Chesapeake Bay and its tributaries (Sadzinski and Webb 1998) and are often caught using bait. Muoneke and Childress (1994) reported that natural baits were often swallowed more deeply by fish than artificial lures and resulted in higher mortality. Siewert and Cave (1990) reported that worm-baited hooks were ingested deeper by bluegill Lepomis macrochirus, resulting in significantly higher mortality (88%) than when the same species was caught with artificial lures (28%).
Fisheries Management Plan stock assessment committees recommend that programs monitor and quantify discard levels. Currently anglers are discarding 75% of the white perch they catch and most are less than 6.5 in. The mortality rate of white perch that are caught and released is not known. If the mortality rate is high for released fish, a minimum size may not be an appropriate management tool.

METHODS

The mortality study was conducted on Unicorn Branch, a tributary to the Chester River. This site, located at a Maryland Department of Natural Resources-Fisheries Service field office, was selected because of its proximity to electrical power and access to a large number of anglers who provided fish as test specimens. White perch stage a spring spawning migration in this stream and concentrate in the spill-way below the dam at the state-owned Unicorn pond.
Recreational anglers were asked to donate white perch they would normally have released. Fish were taken from anglers that used spin fishing gear with shad darts baited with live grass shrimp. All hooks were barbed. This was the most common angling technique used at this site for white perch. Fish were hooked and played normally and if not desired by the angler were placed in a water filled 5.0 gal bucket. Hook location was indicated by hole-punching the caudal fin. Shallow hooked fish, defined as hooked in the lips, mouth or gills, were unmarked. Deep hooked fish, defined as hooked in the gullet or stomach, were marked in the upper lobe of the caudal fin. Foul hooked fish were defined as being hooked in the external surface anywhere posterior to the eyes and were marked in the lower lobe of the caudal fin.  Fish were transported to holding tanks in the buckets.
Two 340 gal circular fiberglass tanks, 5.0 ft wide and 30 in deep were used to hold fish. A central stand pipe drained each tank. Water was supplied to the tanks by means of a 1.0 horsepower electrical pump (115 volts, 10.0 amps). Pump capacity resulted in approximately twelve exchanges of water in each tank each day. Water drawn from Unicorn Branch, was piped under the service road through a culvert and introduced to the tanks above the surface to maximize aeration and at an angle to cause a current into which fish would orient. Water temperature (C) was recorded in both tanks and Unicorn Branch each day. Tanks were covered with locking wooden lids.
White perch were observed daily for mortality. After 48 hours they were measured, sexed, hook location (hole punch position) recorded and then released.

RESULTS

Five hundred and twenty four white perch were used in six trials conducted between March 28 and April 4, 1998. One white perch (0.2%), a 7.6 in female, was lip hooked and died during the first 24 hours after capture during Trial III. All released fish appeared vigorous when released and swam off under their own power. None of the wounds on the foul hooked fish appeared to be infected.
The number of fish in each trial varied due to the number of anglers present at the site and their success. Approximately 56% (292) fish were males. They ranged in total length from 5.3- 9.0 in and averaged 7.2 in. About 44% (232) were females. Female white perch ranged in total length from 6.3-9.6 in and averaged 7.5 in. Most white perch (95.4%) were shallow hooked, 4.4% were foul hooked and 1 fish (0.2%) was deep hooked.
Water temperature increased at a relatively constant rate during the first four trials,  declined slightly during Trial V and leveled off during the last trial. Pump capacity produced approximately 12 exchanges of water each day in each tank. As a result stream and tank temperatures remained the same throughout the entire study. Water temperature was 60F on the first day of the experiment and 67F on the last day. The greatest change occurred during Trial II when the temperature increased from 62-65F. All other trials had a change in temperature of 2F) or less.

DISCUSSION

The mortality among released white perch under the conditions of this study (low water temperatures, no salinity) was very low (0.2%). Only a single fish was deeply hooked and deep hooking is usually a significant contributor to release mortality (Muoneke and Childress 1994). Anglers used grass shrimp (Palaemonetes) on a shad dart. Natural baits alone are more often swallowed deeply and their use can result in higher mortality. The combination of a natural bait on an artificial lure produced a very low rate of deep hooking in this study.
Twenty three fish (4.4%) were foul hooked and all survived. Foul hooking was defined in this study as a hook wound in the outside body anywhere posterior to the eyes. Foul hooked white perch were generally wounded in the back or shoulder area, away from any vital organs.
The white perch spawning migration is initiated by rising water temperatures. The study began when the white perch arrived at the spillway below Unicorn Pond to spawn. Temperature and salinity have been shown to influence the survival of striped bass Morone saxatilis that are caught and released (RMC 1990; Lukacovic and Uphoff 1997). High temperatures and low salinities can increase mortality associated with stress. In this study temperatures remained low and did not appear to exacerbate mortality from stress. Salinity was non-existent at this site.
Average size and size range of fish used in this study were not representative of all fish in the stream because anglers tended to keep larger fish. White perch donated to this study would have been released either because of undesirable size or because anglers were catch-and-release fishing. The criteria that individual anglers used to judge whether a fish was desirable was not consistent. Eighty four percent of the fish used in this study were less than 8 inches. If minimum size regulations or creel limits were to be considered in the future, survival of released fish in the spring spawning run fishery is high enough for these measures to be successful.

LITERATURE CITED

Lukacovic, R. and J. Uphoff. 1997. Hook Location, fish size and seasonality as factors     influencing mortality of striped bass caught with bait in Chesapeake Bay. Maryland     Department of Natural Resources, Fisheries Service, Annapolis, Maryland.

Mouneke, M.I. and M.W. Childress. 1994. Hooking mortality: a review for recreational     fisheries. Reviews in Fisheries Science 2: 123-156.

RMC, Inc. 1990. An evaluation of angler induced mortality of striped bass in Maryland.     Completion Report (P.L. 89-304, AFC-18-1) to National Marine Fisheries Service,     Gloucester, Massachusetts.

Sadzinski, R.A. and E.J. Webb. 1998. Assessment of the 1997 recreational finfish harvests in     the Choptank and Chester rivers and summer head boat surveys. In Piavis, P.G., B.H.     Pyle, A.A. Jarzynski, R.A. Sadzinski, E.J. Webb, C. Markham, J.P. Mower, R.     Lukacovic and D.R. Weinrich. Stock assessment of selected resident and migratory     recreational finfish species within Maryland’s Chesapeake Bay. Federal Aid Project F-    54-R. Annual Report, Department of the Interior, Fish and Wildlife Service.

Siewert, H.F. and J.B. Cave. 1990. Survival of released bluegill Lepomis macrochirus caught     on artificial flies, worms, and spinner lures. Journal of Freshwater Ecology 5:407-411.