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Michael J. Porta

Publications and source records attributed to Michael J. Porta.

5 recordsLinked to original sources
USGS2019

Marking otoliths of Alligator Gar by immersion in oxytetracycline

Alligator Gar Atractosteus spatula are increasingly being stocked to restore populations, making the need to identify stocked individuals important for monitoring. Oxytetracycline (OTC) immersion allows for large numbers of fish to be marked simultaneously, thus eliminating the need to handle fish individually, but protocols for doing so have not been investigated fully for this species. In this study, we sought to identify dosages of OTC (concentration and duration of exposure) that would successfully mark juvenile Alligator Gar while minimizing mortality as a result of the marking procedures. Juvenile Alligator Gar (38 ± 4.4 mm [mean ± SE]) were collected from raceways at Tishomingo National Fish Hatchery 18–22 d after hatch and were marked during transport to the Oklahoma Fishery Research Laboratory. Ten individuals per treatment (360 total individuals) were randomly placed into one of three replicates containing one of four concentration × duration combinations of Pennox 343 OTC solution. Juvenile Alligator Gar were exposed to an OTC concentration of 0 (control), 500, 600, or 700 mg/L for a duration of 4, 5, or 6 h. Asteriscus, lapillus, and sagittal otoliths were examined for mark presence at 14 d postexposure by using fluorescent microscopy. The OTC concentration and duration both affected mean mark quality similarly among otolith types. Mortality increased with increasing OTC concentration, suggesting that a balance between concentration and duration is needed to achieve marking goals. Based on our findings, batch marking of Alligator Gar was successful at OTC concentrations from 500 to 700 mg/L for 4–6 h, although immersion at 500 mg/L for 6 h and 600 mg/L for 4–6 h produced the best balance between high mark quality and low associated mortality.

North American Journal of Fisheries Management↗
USGS2018

Precision of four otolith techniques for estimating age of white perch from a thermally altered reservoir

The White Perch Morone americana is an invasive species in many Midwestern states and is widely distributed in reservoir systems, yet little is known about the species' age structure and population dynamics. White Perch were first observed in Sooner Reservoir, a thermally altered cooling reservoir in Oklahoma, by the Oklahoma Department of Wildlife Conservation in 2006. It is unknown how thermally altered systems like Sooner Reservoir may affect the precision of White Perch age estimates. Previous studies have found that age structures from Largemouth Bass Micropterus salmoides and Bluegills Lepomis macrochirus from thermally altered reservoirs had false annuli, which increased error when estimating ages. Our objective was to quantify the precision of White Perch age estimates using four sagittal otolith preparation techniques (whole, broken, browned, and stained). Because Sooner Reservoir is thermally altered, we also wanted to identify the best month to collect a White Perch age sample based on aging precision. Ages of 569 White Perch (20–308 mm TL) were estimated using the four techniques. Age estimates from broken, stained, and browned otoliths ranged from 0 to 8 years; whole‐view otolith age estimates ranged from 0 to 7 years. The lowest mean coefficient of variation (CV) was obtained using broken otoliths, whereas the highest CV was observed using browned otoliths. July was the most precise month (lowest mean CV) for estimating age of White Perch, whereas April was the least precise month (highest mean CV). These results underscore the importance of knowing the best method to prepare otoliths for achieving the most precise age estimates and the best time of year to obtain those samples, as these factors may affect other estimates of population dynamics.

Oklahoma↗
USGS2009

Ages and lengths of yellow perch Perca flavescens , white perch Morone americana , and lake whitefish Coregonus clupeaformis in commercial trap nets in western Lake Erie

We collected samples of yellow perch (Perca flavescens) and white perch (Morone americana) in spring, and of lake whitefish (Coregonus clupeaformis) in autumn, from commercial trap nets set in western Lake Erie in 2008. The yellow perch sample (N = 153) was dominated (72%, of the total sample) by the 2003 year class, followed by the 2005 year class (12%). The white perch sample (N = 201) was dominated by the 2005 year class (39% of the total sample), followed by the 2003 year class (23%). The lake whitefish (N = 99) sample was dominated by the 2003 year class (75%) followed by the 2001 year class (10%). For yellow perch (both sexes in spring, analyzed separately) and lake whitefish (males in autumn), mean total length at age 5 was the same for the 2001 year class (calculated from historical data) and the 2003 year class.

Lake Erie↗
USGS2009

Surveillance and status of fish stocks in western Lake Erie, 2008

The Lake Erie Biological Station has conducted bottom trawl assessments of fish populations in western Lake Erie near East Harbor State Park, Ohio each summer and autumn since 1961. The catches of most age-0 forage fishes in 2008 were less than their 15-year means. Mean densities for five species exceeded the long term mean. Mean density of age-0 white perch Morone americana was more than double last year’s mean and the long-term mean. Densities of both yellow perch Perca flavescens and walleye Sander vitreus were at or above their long term mean. Catches of round goby Neogobius melanostomus (all ages combined) exceeded the previous five years, but were substantially below the species’ 13-year (1996-2008) mean. For five species, mean total lengths of age-0 individuals captured in 2008 were greater than their respective 20-year means. During 1988-2007, the frequency of occurrence for yellow perch diet items was highest for benthic invertebrates and zooplankton during the summer and benthic invertebrates in autumn. During summer zooplankton and benthic invertebrates were frequently consumed by white perch. Benthic prey for white perch occurred more frequently in the last 5-10 years.

Lake Erie↗