David C. Glover

Prospects for Fishery-Induced Collapse of Invasive Asian Carp in the Illinois River

ABSTRACT Invasive Asian Carp are threatening to enter Lake Michigan through the Chicago Area Waterway System, with potentially serious consequences for Great Lakes food webs. Alongside efforts to keep these fishes from entering Lake Michigan with electric barriers, the state of Illinois initiated a fishing program aimed at reducing their densities through intensive commercial exploitation on the Illinois River. In this study, we explore prospects for the “collapse” of Asian Carp in the Illinois River through intensive fishing. Based on a meta-analysis of demographic data, we developed a dynamic simulation model to compare the performance of existing and alternative removal strategies for the Illinois River. Our model projections suggest that Asian Carp in the Illinois River are unlikely to collapse if existing harvest rates are kept below 0.7 or fishing continues to be size selective (targeting only fish >500 mm or <500 mm) or species selective (targeting mostly Bighead Carp), although their biomasses cou...

Status and Habitat Use of Scaphirhynchus Sturgeons in an Important Fluvial Corridor: Implications for River Habitat Enhancement

AbstractIn the central United States, recovery efforts for populations of the federally endangered Pallid Sturgeon Scaphirhynchus albus have been ongoing since its listing in 1990. Its congener, the Shovelnose Sturgeon S. platorynchus, has also recently been listed as threatened where it overlaps with Pallid Sturgeon. The status of both species in the Mississippi River is unknown and so are habitat enhancement priorities that would benefit their recovery. Using field data collected from 2002 through 2005, we (1) estimated the adult population size of both species using mark–recapture methods and (2) quantified habitat use of these sturgeons with multiple gears to elucidate habitat enhancement priorities in the middle Mississippi River—an important fluvial corridor that connects the upper Mississippi River and Missouri River basins with the lower Mississippi River basin. Population size was estimated to be 1,516 (95% CI = 710–3,463) Pallid Sturgeon (five individuals per river kilometer [rkm]) and 82,336 (9...

Potential of Asian Carp from the Illinois River as a Source of Raw Materials for Fish Meal Production

Abstract Incentivizing overfishing through the creation of high-value markets for Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis has been proposed as a management strategy for controlling Asian carp in the Illinois River. Asian carp may be rendered into a protein-dense fish meal, and one of the most attractive, high-value end uses for such a product is aquafeed manufacturing. However, the nutritional content and shelf stability of Asian carp as a raw material must be determined to assess its suitability for rendering and subsequent use as a protein source in aquafeeds, which was the focus of this study. To determine seasonal, geographical, and species variation in body composition, fatty acids, and oxidative stability, Asian carp were collected from five reaches of the Illinois River during the fall, spring, and summer (up to 12 individuals of each species per reach per season) and analyzed. Slight geographical, seasonal, and species variation exists in the body composition and fatty ...

Characterising and predicting algal blooms in a subtropical coastal lagoon

Algal bloom is a major concern worldwide. In this study, we characterised the physical and biochemical parameters during an algal bloom event in a coastal lagoon in an attempt to predict local blooms in the future. Results showed that the highest concentrations of dissolved inorganic phosphorus (DIP), chlorophyll a (chl a) and phytoplankton abundance were found in the inner area, whereas the highest dissolved inorganic nitrogen (DIN) concentration occurred near the inlet-outlet channel. Chl a was correlated with DIP, and there was a significant exponential relationship between chl a and the nitrogen to phosphorus ratio (N/P ratio) across all sampling stations and times. A higher proportion of the variation in chl a was explained by the N/P ratio than either DIP or DIN. We found that a N/P ratio <2.38 will likely trigger an algal bloom (chl a ≥ 10 µgL–1) in the lagoon. Our results suggest that the N/P ratio could be used as an expedient and reliable measure of the potential eutrophic status of coastal lagoons.

Spatiotemporal Reproduction and Larval Habitat Associations of Nonnative Silver Carp and Bighead Carp

AbstractThe establishment of nonnative Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis (collectively referred to as “bigheaded carp”) in the central United States may have negative ecological consequences and economic impacts. Our objectives were to quantify patterns and habitat associations of adult bigheaded carp reproduction, larval production, and habitat use; such information is important for control strategies and identifying recruitment sources. During May–August 2011, we sampled adults and larvae at 10 sites distributed adjacent to and within the main channel of the Mississippi River at Pool 26 (study area = 28 river kilometers). Female reproductive status, adult location, and larval density were compared to environmental conditions, including temperature, site velocity, and turbidity. Large females spawned earlier than their smaller counterparts. No clear spawning aggregations of adults were observed, suggesting plasticity in staging habitat. Larvae were distributed across all...

A refined electrofishing technique for collecting Silver Carp: Implications for management

AbstractDetecting nuisance species at low abundance or in newly established areas is critical to developing pest management strategies. Due to their sensitivity to disturbance and erratic jumping behavior, Silver Carp Hypophthalmichthys molitrix can be difficult to collect with traditional sampling methods. We compared catch per unit effort (CPUE) of all species from a Long Term Resource Monitoring (LTRM) electrofishing protocol to an experimental electrofishing technique designed to minimize Silver Carp evasion through tactical boat maneuvering and selective application of power. Differences in CPUE between electrofishing methods were detected for 2 of 41 species collected across 2 years of sampling at 20 sites along the Illinois River. The mean catch rate of Silver Carp using the experimental technique was 2.2 times the mean catch rate of the LTRM electrofishing technique; the increased capture efficiency at low relative abundance emphasizes the utility of this method for early detection. The experiment...

Picoplankton dynamics and picoeukaryote diversity in a hyper-eutrophic subtropical lagoon.

Picoplankton (cells with a diameter of 0.2–3.0 μm) is the dominant contributor to both primary production and biomass in the ocean. Most of the previous studies on picoplankton have been conducted in the oligotrophic open sea with few in the eutrophic area. In this study, we investigated the dynamics of different groups of picoplankton and the diversity of picoeukaryote (based on 18S rDNA) in a hyper-eutrophic marine coastal lagoon. The results indicated that temperature and phosphate concentration were most responsible for the dynamics of different picoplankton groups. Examination of 135 clones revealed 27 different Denaturing Gradient Gel Electrophoresis (DGGE) patterns. At least 7 high-level taxonomic groups of picoeukaryote were recorded. The picoeukaryotic diversities included Alveolates, Stramenopiles, Haptophyceae, and Viridiplantae, with Stramenopiles being the most diverse group. Overall the results of this study indicated that picoplankton diversity was low relative to studies conducted in more oligotrophic waters.

Differential Seasonal Steroid and Gonadotropin Expression in Full-Sibling Female Channel Catfish Maturing at Two or Three Years of Age under Normal and Accelerated Thermoperiods

AbstractThe present study was designed to determine whether female Channel Catfish Ictalurus punctatus exhibiting accelerated maturation display similar steroid (estradiol and testosterone) and gonadotropin (luteinizing hormone and follicle-stimulating hormone [FSH] messenger RNA) profiles within the first reproductive period compared with full-sibling females that reached maturity 1 year later. The accelerated maturation (AM) fish were maintained under a shortened annual temperature cycle, consisting of 4 months in 26°C water followed by 2 months at 13–14°C, repeated for three cycles. In 2007, 2-year-old AM fish were 12 times more likely to spawn on any given day than the normal maturation (NM) fish. The 2-year-old NM group was 21 times more likely to spawn as 3-year-old fish in 2008 than in the previous year, 2007. In 2007, NM fish had higher body mass in January, March, and May and maintained higher gonadosomatic index (GSI). Two-year-old AM fish never had significantly higher levels of any measured va...

Decapod community structure in a subtropical mountain stream in Taiwan before and after a catastrophic typhoon

Extreme events (typhoons, floods, and mudflows) can influence the abundance and community structure of aquatic organisms. In this study, we compare freshwater decapod abundance and community structure in main channel and tributary sites in a subtropical area of Taiwan before and after the typhoon Tembin. The results indicate that the physical conditions, decapod abundance and the Shannon diversity index were significantly different between the main channel and tributary sites, but were not significantly affected by the typhoon. The decapod community structure also showed significant differences spatially, but not temporally. The results of this study suggest that decapod communities are highly resilient to the acute effects of typhoons.