Arnold G. Eversole

A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10+ Years of Increased Awareness

Abstract The American Fisheries Society Endangered Species Committee herein provides a list of all crayfishes (families Astacidae and Cambaridae) in the United States and Canada that includes common names; state and provincial distributions; a comprehensive review of the conservation status of all taxa; and references on biology, conservation, and distribution. The list includes 363 native crayfishes, of which 2 (⟨ 1%) taxa are listed as Endangered, Possibly Extinct, 66 (18.2%) are Endangered, 52 (14.3%) are Threatened, 54 (14–9%) are Vulnerable, and 189 (52.1%) are Currently Stable. Limited natural range continues to be the primary factor responsible for the noted imperilment of crayfishes; other threats include the introduction of nonindigenous crayfishes and habitat alteration. While progress has been made in recognizing the plight of crayfishes, much work is still needed.

Intensification of pond aquaculture and high rate photosynthetic systems

Abstract Aquaculture production systems may range from tanks and raceways, in which water quality is controlled by water dilution and discharge to the environment to captive water systems, in which water quality is controlled by microbial reactions within the tank or pond. Attempts at intensification of pond aquaculture beyond the commonplace practice of supplemental aeration may be classified into categories of physical/chemical techniques and a broad range of microbial techniques. Most of these techniques are directed at raising the ‘ceiling’ of the system ammonia detoxification rate. Physical–chemical techniques for intensification of pond aquaculture have included use of in-pond cages and raceways, water blending and shading of the algal community, as well as, direct flocculation and removal of algal and bacteria biomass from ponds. A variety of microbial processes can be used to reduce ammonia levels in a conventional pond. These processes include nitrification/denitrification, photosynthesis, and heterotrophic bacterial re-growth. In this paper, simplified microbial growth fundamentals, and elemental mass balances are used to analyze and compare the various aquaculture intensification techniques and, in particular, to compare conventional and heterotrophic techniques to the use of high rate photosynthetic systems. Direct or indirect photosynthetic systems include enhanced algal systems (with water mixing), polyculture, hydroponics, wetlands, and terrestrial irrigation/fertilization. The development of Clemson Universitys Partitioned Aquaculture System (PAS) constitutes an attempt to combine a number of the various physical, chemical, and microbial intensification techniques into a single integrated system. The PAS represents an adaptation of high rate microalgal culture to produce a sustainable, minimal discharge, high yield, and more controllable fish production process. The PAS combines the advantages of process control of recirculating tank aquaculture with the lower costs of earthen pond aquaculture. Central to the economic success of the PAS is the use of low speed (1–3 r.p.m.) paddlewheels as an energy efficient means of establishing a uniform water velocity field within an aquaculture pond. The PAS represents a redesign of the conventional aquaculture pond culture technology providing a spectrum of applications ranging from moderate yield (6700–11 200 kg/ha) ‘engineered ecosystems’ to high yield (16 800–33 600 kg/ha) controlled ‘production processes’. This high rate photosynthetic system offers the potential for a 90% reduction in total water usage per unit of fish produced. The modular nature of the PAS, the increased productivity per unit area, reduced water requirement, and reduced environmental impact offers the potential for fish culture systems to be installed at sites not currently suitable for conventional aquaculture.

Filtration of green algae and cyanobacteria by Nile tilapia, Oreochromis niloticus, in the Partitioned Aquaculture System

Abstract Nile tilapia, Oreochromis niloticus , held in a timed pulse fed Continuous Stirred Tank Reactor (CSTR) were provided Partitioned Aquaculture System (PAS) algal-rich water dominated by green algae (i.e., Scenedesmus and Ankistrodesmus ) and cyanobacteria (i.e., Microcystis and Merismopedia ) to determine filtration rates (FR). A similar number and size of tilapias were stocked at 1.5 kg/tank into each of the six CSTRs (127 l) for 58-h experiment period. The cell counts of phytoplankton in water filtered by tilapias indicated significant reduction in green algae and cyanobacteria. Nile tilapia was more effective filtering the larger particle size taxa in both water sources. FR measured as mg of particulate organic carbon (POC) per kg wet fish weight per hour increased as POC increased. A curvilinear filter-feeding rate model provided a maximum filtration rate (FR max ) of 641 mgC/kg/h at 26 mgC/l in green algal-dominated water. The projected FR max of cyanobacterial-dominated water was 865 mgC/kg/h at 59 mgC/l. The derived filter-feeding rate models will help to describe Nile tilapia filtration kinetics in the PAS and the potential for control of nuisance cyanobacteria.

Effects of size and temperature on mud crab,Panopeus herbstii, predation on hard clams,Mercenaria mercenaria

Predation byPanopeus herbstii onMercenaria mercenaria was significantly affected by temperature, and the size of predators and prey items. LargerP. herbstii opened more clams and preyed more successfully on larger clams than did smaller crabs. Increase in seed clam size and decrease in water temperature significantly reduced predation. Clam size appeared to be more important than crab satiation in reducing predation rate. Planting larger seed clams in cooler months should help to improve clam survival by reducing the impact ofP. herbstii in culture operations.

Comparative Nile tilapia and silver carp filtration rates of Partitioned Aquaculture System Phytoplankton

Abstract Nile tilapia ( Oreochromis niloticus ) and silver carp ( Hypophthalmichthys molitrix ) held in timed-pulse feeding chambers were provided water dominated either by green algae ( Scenedesmus , Ankistrodesmus and Tetraedron ) or by cyanobacteria ( Microcystis ) to compare filtration rates (FRs). FRs were expressed as suspended particulate organic carbon (POC)/kg wet fish weight/h and as phytoplankton units filtered based on counts. Nile tilapia and silver carp filtration significantly reduced phytoplankton number of both taxonomic groups with the larger phytoplankton being filtered proportionally more than the smaller phytoplankton. Nile tilapia FR of green algae was significantly higher than silver carp; however, silver carp FR of cyanobacteria was higher than Nile tilapia. Ivlevs 90% saturation FRs (FR 90 ) in green-algal and cyanobacterial water sources were 702 and 812 mgC/kg/h for Nile tilapia and 414 and 1028 mgC/kg/h for silver carp, respectively. Silver carp were observed to reach these FR 90 values at lower POC concentrations than Nile tilapia with both green algae and cyanobacteria.

Age, growth, and sex ratio of American eels in brackish-water portions of a South Carolina River

Abstract American eels Anguilla rostrata (yellow phase; N = 462) collected from brackish-water portions (range of salinity: 0–23‰) of the Cooper River, South Carolina, ranged in length from 26.0 to 68.7 cm and in weight from 32 to 767 g. The length-weight relationship is log10W = -5.85 + 3.07 log10L; W = wet weight (g) and L = total length (mm). Age estimates (inland years) from 442 pairs of otoliths indicated a mean age of 4.3 years and range of 1–12 years. Growth of American eels from brackish-water areas of the Cooper River was faster than growth of the species from northeastern United States and Canada. American eels from this southern habitat appear to migrate back to sea after ages 6–7, sooner than eels from northern locations. Histological examination of gonads from 458 specimens revealed that females outnumbered males 23 to 1. These results were consistent with most previous investigations and suggest that females dominate American eel populations in brackish-water and freshwater habitats in North...

19 Partitioned aquaculture systems

Publisher Summary Low capital cost and the relative reliability offish production are the major advantages offish culture in earthen ponds. Disadvantages of pond production are the need for continuous management of dissolved oxygen concentrations, as well as other fluctuating water quality variables. Labor requirements (especially for harvesting) and problems with off-flavors, predators, and diseases represent additional management difficulties. These issues, combined with land, water, and environmental resource constraints, have stimulated a search for technological improvements in aquaculture practices. Shifting production to more energy-intensive systems is one solution, either through application of increased aeration (2 to 38 kW/ha; 1 to 20 hp/acre) in ponds, or by abandoning the land-intensive pond altogether and shifting production to higher density recirculating tank or raceway systems. Researchers and producers have made significant efforts to address the need for intensification of pond aquaculture while minimizing environmental impacts. Pond aquaculture productivity is limited first by oxygenation of the water column and second by accumulation of ammonia to levels toxic to the cultured organisms.

Tag Retention, Growth, and Survival of Red Swamp Crayfish Procambarus clarkii Marked with Coded Wire Tags

Abstract Juvenile red swamp crayfish (or crawfish), Procambarus clarkii (20–41 mm in total length) were collected from a crayfish culture pond by dipnetting and tagged with sequentially numbered, standard length, binary-coded wire tags. Four replicates of 50 crayfish were impaled perpendicular to the long axis of the abdomen with a fixed needle. Tags were injected transversely into the ventral surface of the first or second abdominal segment and were imbedded in the musculature just beneath the abdominal sternum. Tags were visible upon inspection. Additionally, two replicates of 50 crayfish were not tagged and were used as controls. Growth, survival, and tag retention were evaluated after 7 d in individual containers, after 100 d in aquaria, and after 200 d in field cages. Tag retention during each sample period was 100%, and average mortality of tagged crayfish within 7 d of tagging was 1%. Mortality during the remainder of the study was high (75–91%) but was similar between treatment and control samples...

AGE AND GROWTH OF THE KNOBBED WHELK BUSYCON CARICA (GMELIN 1791) IN SOUTH CAROLINA SUBTIDAL WATERS

Abstract Knobbed whelk, Busycon carica (Gmelin, 1791), age and growth were estimated using tagged and recaptured individuals (n = 396) from areas off South Carolina coastal islands. Recaptured whelks were at large an average of 298 d (4–2,640 d). Growth, an increase in shell length (SL), was evident in 24% of the recaptured whelks, whereas 29% of recaptured individuals were the same size as when released and 47% were smaller than the released size. Mean growth rate was <0.001 mm SL/d and 0.022 mm SL/d if decreases in SL were assumed to be zero. Smaller whelks (≤90 mm SL) at large for over one year grew seven times faster than larger whelks. The von Bertalanffy growth model: SLt = 159.5(1 − e−0.0765(t+0.4162)), was developed from the mark—recapture whelks exhibiting growth. Based on a South Carolina minimum legal size of 102 mm SL, whelks recruit into the fishery at 13 y of age. The longevity, large size at maturity and slow growth suggest the potential for over harvest of knobbed whelk. Future whelk management plans may wish to consider whether economically viable commercial harvest can be sustainable.

Technical Notes: Toxicity of Ammonia to Fingerling White Bass: Effect of Selected Environments on Uptake Dynamics

Abstract The 96-h median lethal concentration of un-ionized ammonia-nitrogen for fingerling white bass Morone chrysops (mean weight ± SD, 4.4 ± 1.42 g) at 19.7 ± 0.4°C was 0.63 ± 0.17 mg/L in soft (≤5.0 mg calcium/L) freshwater. The uptake of ammonia by fingerling white bass (mean weight, 14.0 ± 2.74 g) was similar in soft freshwater, hard (78.3 ± 3.80 mg calcium/L) freshwater, and dilute (7.4 ± 0.30 g sea salt/L) seawater. However, exposure time did affect the concentration of plasma ammonia in exposed white bass. Based on the observations in this study and others, it is estimated that growth of fingerling white bass should not be inhibited if fish are continuously exposed to un-ionized ammonia nitrogen at 0.06 mg/L or less.