Thomas E. Brooking

Comparison of Angler and Cormorant Harvest of Walleye and Yellow Perch in Oneida Lake, New York

Abstract Since at least the beginning of the last century, sport anglers and commercial fishers have often held cormorants responsible for declining catches. The recovery of double-crested cormorant Phalacrocorax auritus populations throughout the Great Lakes region since the late 1970s has rekindled efforts to assess their impact on sport fish populations. In this paper we compare the species and age composition of fish consumed by double-crested cormorants (diet study) and harvested by anglers (creel survey) with abundance estimates of walleyes Stizostedion vitreum and yellow perch Perca flavescens (mark-recapture and catch per unit effort). The numbers of walleyes consumed by cormorants were similar to those harvested by anglers; however, cormorants consumed only subadults, whereas anglers harvested only age-4 and older adults. Cormorants and anglers combined harvested 7% of age 1-3 walleyes and 14% of the adult walleye population. Cormorant consumption of adult yellow perch was similar to angler harve...

Size-Dependent Alewife Predation on Larval Walleyes in Laboratory Experiments

Abstract Alewives Alosa pseudoharengus can be significant predators on larval fish, and fishery managers must consider potential predation when developing stocking strategies. We conducted laboratory experiments to determine sizes of larval walleyes Stizostedion vitreum that alewives can capture. Adult alewives (122 ± 1.52 mm total length, TL) preyed intensely on larval walleyes from the time the larvae hatched until they reached about 16 mm TL. All larval walleyes smaller than this size were captured on the first strike by an alewife. Avoidance behavior by larval walleyes was first observed when they reached 16–19 mm TL, and although some survived the first strike, all were consumed by the end of 1 h. When larvae averaged about 25 and 30 mm TL, few were captured on the first strike, and 75% and 33%, respectively, were consumed within 1 h. When larvae were about 34 mm TL, only 5% were eaten by the end of 1 h. Alewife gape height and width were both about twice as large as the largest larval walleye body h...

Survival and Growth of Intensively Reared Large Walleye Fingerlings and Extensively Reared Small Fingerlings Stocked Concurrently in Small Lakes

Abstract Size of walleyes Stizostedion vitreum at the time of stocking is thought to play a key role in determining the success of stocking programs. Because starvation and predation risk are size-dependent processes, fingerlings stocked at larger sizes are expected to survive better than fingerlings stocked at smaller sizes. However, large fingerlings often require different culture techniques that make them more expensive to produce. Therefore, large fingerlings should only be used if returns are high enough to offset costs. We evaluated the relative success of two sizes of stocked walleye fingerlings in four lakes in New York State. For four consecutive years (1993–1996), each lake was stocked with equal densities (50 fish/ha) of small (30–50-mm), extensively reared pond fingerlings in June and large (120–140-mm), intensively reared fall fingerlings in September. In October, we electrofished each lake to determine growth and survival of stocked fingerlings. Despite being stocked at a much later date, a...

First occurrence of the mysid Hemimysis anomala in an inland lake in North America, Oneida Lake, NY

ABSTRACT Hemimysis anomala (Crustacea, Mysidae) is a recent invader to North America that until now was reported only from the Laurentian Great Lakes and their immediate embayments, along with the St. Lawrence River. In August 2009, we identified Hemimysis in diets of white perch and yellow perch in Oneida Lake, NY. Night time vertical plankton net tows detected Hemimysis at four sites across the lake. Hemimysis in fish diets (5.5– 8.6 mm) were larger than in net tows (2.2–7.0 mm) and reproduction is occurring as some females had brood sacs. This is the first documented introduction of Hemimysis to an inland lake in North America, outside the Great Lakes. Oneida Lake is located 53 river km upstream from Lake Ontario, the nearest known source of Hemimysis. No genetic differences were found between Hemimysis in Oneida Lake and Lake Ontario, indicating this is likely the source of introduction. Several large rapids, locks, and dams separate the two lakes, and as a result the most likely vector of introduction to Oneida Lake is pleasure boat or light commercial traffic via the canal system or overland transport. The presence of Hemimysis in Oneida Lake 3 years after it was first found in Lake Ontario suggests this species may spread rapidly throughout the basin. Despite an intensive monitoring program on Oneida Lake directed at fish, Zooplankton, and limnology, Hemimysis was only detected in fish diets and night time Zooplankton tows, indicating it may go undetected in lakes for some time using traditional daytime net tows.

Food web effects and the disappearance of the spring clear water phase in Onondaga Lake following nutrient loading reductions

Abstract The annual spring clear water phase (May–June) in Onondaga Lake, New York, unexpectedly disappeared in 2003 following several years of phosphorus and ammonia loading reductions at the Metropolitan Syracuse Wastewater Treatment Facility (Metro). Mean chlorophyll a concentration during May–June was higher from 2003 to 2007 than from 1990 to 2002, with mean Secchi disk depths <2 m. Large zooplankton (Daphnia sp.) were abundant during April–June before 2003 but were rare from 2003 to 2007, while abundance of small zooplankton (Bosmina longirostris) increased. Alewife (Alosa pseudoharengus) catches from electrofishing surveys dramatically increased in 2003, and hydroacoustic surveys estimated the alewife population to be between 1600 and 2300 fish/ha in spring 2005–2007. The alewife population in 2005 was dominated by a strong 2002 year class. Increasing biomass of the 2002 year class coincided with the timing of the shift from large to small zooplankton in late summer of 2002. This indicates that the strong 2002 alewife year class initiated a classic trophic cascade in Onondaga Lake, causing the decline and continuing low abundance of Daphnia sp. and the disappearance of the spring clear water phase. The increase in alewife may have been associated with decreasing ammonia concentrations following improvement to Metro. Unionized ammonia has been below levels considered toxic to nonsalmonid fish species since 1999, and the ammonia concentration continues to decrease in the lake. Thus, reductions in nutrient loading can lead to unanticipated food web effects causing decreases rather the expected increases in water clarity in the spring–early summer period.

Angler Catch Rates and Catchability of Walleyes in Oneida Lake, New York

Abstract Understanding the relationship between anglers and fish is important to the management of angling fisheries. We compared angler catch rates estimated from creel surveys with (1) population density estimates of age-3 and older walleyes Sander vitreus based on mark–recapture and (2) mean growth of walleyes aged 4–6 in Oneida Lake during 1957–1959, 1997, and 2002– 2003. We also compared walleye catchability to walleye population density. Angler catch rates were not related to walleye population density; however, by combining population density and walleye growth, we were able to explain 97% of the variability in angler catch rates, perhaps because growth rates were related to prey abundance. Catchability of walleyes decreased as population density increased. Consideration of these effects should improve our understanding of angler–fish dynamics and allow fishery managers to better predict the effects of management actions.

Analysis of Compensatory Responses in Land-Locked Alewives to Walleye Predation: A Tale of Two Lakes

Abstract We compared one established population (Cayuta Lake) and one expanding population (Canadarago Lake) of landlocked alewives Alosa pseudoharengus to evaluate compensatory responses of alewives to predation by walleyes Sander vitreus. Alewives have been present in Cayuta Lake since at least 1977, and during the years 1995 to 2009 the population ranged from 24,470 fish/ha in 2000 to 3,800 fish/ha in 2007. Alewives were first observed in Canadarago Lake during 1999, and the population remained at low densities (<26 fish/ha) until reaching 370 fish/ha in 2006 and 1,050 fish/ha in 2009. Differences in zooplankton reflected higher planktivory rates in Cayuta Lake than in Canadarago Lake. Density of age-3 and older walleyes was higher in Canadarago Lake (21–24 fish/ha) than in Cayuta Lake (12–14 fish/ha), despite elevated stocking rates of fingerling walleyes in Cayuta Lake during 2002–2006. Alewife density explained 77–84% of the variation in alewife length at age and 48–84% of the variation in condition...

Overwinter Mortality of Gizzard Shad: Evaluation of Starvation and Cold Temperature Stress

Abstract Overwinter mortality of gizzard shad Dorosoma cepedianum has been attributed to starvation, cold stress, and predation; however, the interactions among these factors are not well understood and can change across winter. We evaluated possible causes for overwinter mortality of age-0 gizzard shad through a combination of experiments and field sampling during the winters of 2005–2006 and 2006–2007. In the first experiment, gizzard shad were placed into cages in Oneida Lake, New York, during three time periods prior to ice formation. The fish exhibited low mortality at temperatures above 8°C but high mortality (>75%) in all cages as temperature dropped below 8°C. We observed no consistent patterns of length-dependent mortality or changes in total percent dry weight (DW). However, the viscerosomatic index (VSI) decreased during all time periods, indicating disproportionate use of visceral tissues. In the second experiment, gizzard shad were exposed to temperature treatments of 1, 2, and 4°C in experim...

Hydroacoustic Target Strength Distributions of Alewives in a Net-Cage Compared with Field Surveys: Deciphering Target Strength Distributions and Effect on Density Estimates

Abstract Acoustic estimation of fish abundance requires knowledge of the target strength (TS) distribution associated with the fish present. We measured the TS distribution at 70 kHz for five size-groups of alewives Alosa pseudoharengus (mean total length = 68-138 mm) swimming freely in a large net-cage. Although the mean and mode of the distributions were significantly related to fish length, the TS range obtained from each length-class was over 25 decibels (dB). The TS distributions were negatively skewed and had a tendency toward bimodality. The TS distributions at 70 and 123 kHz were similar for one alewife size-group that was measured with both frequencies. Small but inconsistent differences were found between day and night for the same groups of fish. Shapes of the TS distributions were similar when centered on the mode, and we derived a probability density function (PDF) for TS at 70 kHz as a function of fish length to describe these distributions. We used this PDF to predict TS distributions based...

Influence of Party Size and Trip Length on Angler Catch Rates on Oneida Lake, New York

Abstract Angler catch rates have been used to compare angler success in sport fisheries among years or systems, to assess relative fish abundance, and to evaluate management efforts. Understanding the factors that influence angler catch rates is critical for the proper interpretation and application of these data. Information for 10,998 angler trips was collected through an angler diary program conducted during 1994–1998 and direct-contact roving creel surveys conducted during 1997 and 2002–2004 to examine the influences of angler party size and trip length on the catch rates for walleye Sander vitreus, smallmouth bass Micropterus dolomieu, and yellow perch Perca flavescens at Oneida Lake, New York. Party size and trip length were correlated; therefore, we constructed separate models combining data for year, party size, and trip length to examine the relationship between these factors and the angler catch rate. In both the diary program and the creel survey, the angler catch rates for all species decrease...