Note:  The following article was written in 2002 by Maryland DNR Fisheries Biologist Rudy Lukacovic and condensed in March 2011 for Careful Catch readers by the author.  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.

Recreational Catch-and-Release Mortality of Yellow Perch During Their Spring
Spawning Migration.
Prepared by: Rudy Lukacovic


Management of recreationally important fish generally involves the use of such tools as minimum size restrictions, creel limits and/or closed seasons or areas. Currently yellow perch Perca flavescens caught by recreational fishermen in Maryland’s tidal waters are regulated by all of these management options.
Yellow perch caught by recreational anglers in Maryland’s tidal rivers are protected by a size limit and a creel limit. A (9 in) minimum size limit is required for yellow perch caught from the tidal waters of Maryland’s Chesapeake Bay, except those closed to harvest. Harvest is prohibited in the Magothy, Nanticoke, Patapsco, Severn, South and West rivers. A five fish per day creel limit is in effect for all open tidal waters.
Recreational anglers fishing the spawning tributaries in spring have increasingly focused on yellow perch. In 1998, 9.7% of interviewed anglers fishing the Choptank and Chester rivers targeted yellow perch (Webb and Zlokovitz 1999). In 1999, 37% were targeting yellow perch (Zlokovitz and Webb 2000).
Yellow perch comprised 29% of the total of all species caught (harvested and released combined) by anglers fishing the Choptank and Chester rivers in 1999 (Zlokovitz and Webb 2000). White perch Morone americana represented another 67%. However, harvested catch consisted of 80% white perch and only 17% yellow perch. In both systems 88% of the yellow perch caught by recreational anglers were released. This difference in percent harvested is reflective of there being no size limit for white perch and a relatively high one for yellow perch.
Fisheries management plan stock assessment committees recommend that programs monitor and quantify discard levels. Yellow perch are a highly sought-after recreational species in Maryland’s Chesapeake Bay tributaries during their spring spawning migrations. Currently anglers are discarding 88% of the yellow perch they catch while the mortality rate of sub-legal (< 9 in) yellow perch that are caught and released is not known. A study was undertaken during spring 2002 to quantify losses and identify factors contributing to these losses. This data would provide management with information regarding the effectiveness of size and creel limits for this fishery.


A tank system to hold caught-and-released yellow perch was set up on Wye Stream, a tributary to the Wye River East. This site, located at the Maryland Department of Natural Resources, Wildlife Management Wye Mills field office, was selected because of its access to a large number of anglers who would provide fish as test specimens. Yellow perch stage a spring spawning migration in this stream and concentrate in the spill-way below the dam at the state-owned Wye Pond.
Two 340 gal circular fiberglass tanks were used to hold fish. Water was supplied to each tank by means of separate siphons pulling water from the pond. Flow to each tank was approximately 7 gal per minute. A central stand pipe drained each tank. Water temperature was recorded in both tanks and Wye Stream each day. Tanks were covered with locking wooden lids.
Recreational fishermen, representing a variety of angling experience, were asked to donate yellow perch they would normally have released. Fish were taken from anglers that used spin-fishing gear with shad darts baited with live grass shrimp (Palaemonetes spp.) or minnows (Fundulus spp.). All hooks were barbed. This was the most common angling technique used at this site for yellow 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. Fish were transported to holding tanks in the buckets.
Yellow perch were observed daily for mortality. After 48 hours, the surviving fish were measured, sexed, hook location was recorded and released. Temperature was recorded each day in the tanks and in the stream below the test site.


Cooperating anglers provided 241 yellow perch for the study. These fish were used in nine 48-hour trials that began on March 2 and continued through March 18, 2002. Number of fish used in each trial was dependent on number of anglers and their success. Yellow perch used per trial varied from five to 53. Yellow perch averaged 9.1 in total length and ranged in size from 6.6 – 11.9 in. Male yellow perch were predominant in the catch, representing 87.6% of the fish used in this study. Female yellow perch represented 11.2% of the test fish and 88.9% of those females had already spawned at the time of capture. Sex could not be determined for three yellow perch (1.2%). More than half of the test fish (56.8%) were greater than the minimum legal size 9 in.
Among the sub-legal fish (n= 104), males were the predominant sex, representing 91.3% of that group. Females accounted for 6.7% of the sub-legals and the remainder (1.9%) were unknown.  All sub-legal females were spent.
Anglers also caught pumpkinseed sunfish Lepomis gibbosus, black crappie Pomoxis nigromaculatus, brown bullhead Amerius nebulosus, largemouth bass Micropterus salmoides, and golden shiner Notemigonus crysoleucas. Most of these fish were of undesirable size and were released. Largemouth bass were closed to harvest.
The deep-hooking rate for all yellow perch was 5.8%. Deep-hooking rates ranged between trials from 0.0% to 60.0%. Deep hooking occurred less than 12.5% of the time during all trials except one trial with a small sample size (Trial 5). Among sub-legal yellow perch deep-hooking occurred 8.7% of the time.
Deep-hooking mortality was 35.7% for all yellow perch. Sub-legal yellow perch that were deeply hooked died 33.3% of the time. Shallow-hooking mortality was 0.9% for all yellow perch. No shallow-hooked sub-legal yellow perch died in any trial. Overall mortality in this study, and mortality of sub-legal yellow perch was the same (2.9%).
Water temperatures in Wye Stream ranged from a low of 42.1°F in Trial 2 to 57.6°F in Trial 9. Water temperatures in the tanks differed slightly from stream water temperatures during some trials. The maximum difference in temperature between the stream and the tank was 1.8°F and there was no difference in the temperatures in three trials. The greatest change in tank water temperature during any one 48-hour trial occurred during Trial 9 (+5.4°F).


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. Length limits may also provide quality fishing by preventing the harvest of smaller individuals and allowing a greater number of fish to survive to a more desirable size. Creel limits reduce fishing mortality if they are less than the typical angler catch. Minimum size limits and creel limits assume a high rate of survival among released fish.
Mortality among released yellow perch under the conditions of this study (low water temperatures, no salinity) was low (2.9%). Anglers used grass shrimp or minnows on a shad dart. The combination of a natural bait on an artificial lure produced a fairly low rate of deep hooking among all yellow perch in this study (5.8%) as well as among the sub-legal fish (8.7%).  A study evaluating catch-and-release mortality for white perch on their spawning migration in Unicorn Branch, a tributary of the Chester River, showed anglers using similar terminal tackle shallow hooked their fish 95.4% of the time (Lukacovic 1999). Muoneke and Childress (1994) report that natural baits are often swallowed more deeply by fish than artificial lures and their use results in higher mortalities. Siewert and Cave (1990) reported that worm-baited hooks were ingested deeper by bluegill, resulting in significantly higher mortality (88%) than when the same species was caught with artificial lures (28%).
Shallow hooking mortality was extremely low in this study. Sub-legal yellow perch that were shallow-hooked experienced no mortality and only two of 227 yellow perch (0.9%) greater than the minimum size of 229 mm died. Size-related mortality among shallow-hooked striped bass caught in warm water has been documented in several catch-and-release studies (RMC 1990, Lukacovic and Uphoff 1997).  Larger fish fight longer and are more difficult to handle than smaller fish. Differences in the ratio of gill surface area to body volume increase as fish get larger. Therefore larger fish have a more difficult time eliminating carbon dioxide from their bloodstream and re-oxygenating their tissues after extreme physical exertion. However, for striped bass caught at low water temperatures fish size was not a factor. (Lukacovic and Florence 1999).
Deep-hooking mortality, as expected, was markedly higher, 35.7%. The physical injury associated with swallowed hooks caused profuse bleeding that was clearly visible in most cases. Mortality was extremely rapid as most deaths among deep-hooked fish were documented with minutes. Significant differences in mortality between deep and shallow hooked fish have been consistently documented in catch-and-release mortality studies (Siewart and Cave 1990, Bugley and Shepard 1991,  May 1973, Lukacovic and Uphoff 1997, Lukacovic 2000).
The yellow perch spawning migration is initiated by rising water temperatures. Fish migrate from estuarine areas of tidal tributaries such as Wye River into upper freshwater reaches.  Spawning generally begins when water temperatures reach 44°F; Piavis 1991). Temperatures during Trial 1 were 43.5 – 47.5F, then decreased during Trial 2. This experimental site may have been subject to more rapid changes in water temperature than some other spawning streams. Water is supplied to Wye Stream from the surface of Wye Pond, a 48 acre state-owned lake. Diurnal heating and cooling of the surface water of the lake resulted in more rapid changes in water temperature in the spillway than in other streams that are not affected by a large shallow body of water immediately upstream. The study began when the yellow perch arrived at the spillway below Wye Pond to spawn. Temperature and salinity have been shown to influence the survival of striped bass 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. Yellow perch donated to this study would have been released either because of sub-legal or 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.
Man-made impediments to migration in some spawning streams, such as the dam at Wye Pond or beaver dams will cause fish to concentrate below these structures. This site at Wye Mills was selected because of high angler participation in this fishery and high rates of angler success. Also access to Wye Pond provided sufficient height difference in water levels to produce enough head pressure needed to run the siphon system.
A similar experimental design has been used successfully in previous catch-and-release studies conducted by Maryland’s Fisheries Service. These studies have evaluated recreational release mortality using artificial lures (sometimes with natural bait added) under similar environmental conditions (low water and air temperatures and freshwater, i.e. no salinity). American shad Alosa sappidissima caught by recreational anglers using unbaited shad darts below Conowingo Dam on the Susquehanna River in 1997 experienced a 48 hr mortality of less than 1% (Lukacovic 1998). Hickory shad Alosa mediocris caught and released by fly fishers in Deer Creek suffered no mortality after 48 hrs (Lukacovic and Pieper 1996). White perch caught on baited shad darts experienced release mortality <1% (Lukacovic 1999). Low mortality was anticipated for yellow perch in this experiment.
Maryland regulations require barbless hooks to be used when targeting yellow perch in tidal waters. An informal query of fishers at Wye Stream indicated only one of approximately 30 anglers asked were aware of this regulation. Barbless hooks can reduce handling time when removing the hook from fish. There is no evidence to suggest that they reduce deep hooking. Under the environmental conditions recorded in this experiment, shallow-hooking mortality was low; less than 1% for all fish, and 0% for sub-legal fish. Therefore, no substantial increase in survivorship would be gained by reducing handling time.
Even though sub-legal fish represented less than half of the fish used in this study (43.2%) they represented almost two thirds of the deep hooked fish (64.3%). Smaller fish may be more competitive and exhibit  more aggressive feeding behavior.
The majority of the yellow perch sport-fishery occurs during spring with cool air and water temperatures. Survival rates of both legal and sub-legal sized yellow perch are high enough under these circumstances, that size and creel limits appear to be effective management practices for this species.

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