John G. Riley

A closer look at the bacteriology of nitrification

The mineralizing ability of nitrifying bacteria is well known among aquaculturists, but the underlying bacteriology is abstruse. The proceeding literature review details sources of nitrogenous fish waste and peculiarities of the Nitrobacteraceae family, including survival mechanisms, frailties, and intrinsic kinetics. Fundamental catabolic and anabolic reactions are elucidated, as is the implication of reducing power allotment for respiratory efficiency. Attention is paid to the paramount role of nitrifiers in biofiltration and recommendations are made for future recirculating aquaculture research.

Quality evaluation of American lobsters fed diets containing crab processing waste

Abstract The objectives of this study were to evaluate the effects of incorporating wet crab processing waste (CW) into pelleted feeds on (1) weight gain; (2) shell strength; (3) sensory quality; and (4) proximate composition of American lobsters. Soft shell lobsters were fed one of three pelleted diets (0%, 20% or 40% CW) or a cod rack control (industry standard diet) for 6 weeks. Lobsters fed the 40CW diet had similar weight gains to those fed the control diet. Lobsters fed the CW diets had higher concentrations of shell ash and calcium compared to the controls, however, lobsters from the control treatment had significantly stronger shells as measured by compression to fracture. Sensory analyses revealed no adverse affect of the 40% CW diet on texture or flavor of tail meat. Protein and lipid composition of lobster tail meat was not significantly affected by dietary treatment.

A Low-Flow Self-Cleaning Drainage System for Fish Rearing Tanks

Abstract A float–stopper mechanism was designed to drain fish holding tanks directly from the bottom. Unlike traditional, top-drawn standpipe systems, it allows continuous flushing of settled solid waste. It also prevents the accumulation of these wastes between the two standpipes that are used in bottom-drawn, double-walled standpipe systems. When suspended solids are forced upward between the outer and inner standpipes of such systems, a minimum velocity must be maintained to prevent sediment accumulation. This minimum velocity determines the minimum flow rate through the tank. The system described in this report flushes well over a wide range of flow rates.

Photoelectric measurement of lobster (homarus americanus) response to feed attractants

Abstract The apparatus described was designed to measure the speed and direction of lobster response to feed attractants with minimal observer influence on the test animal. Lobster activity was monitored in an 84 × 10 × 10 in (213 × 25 × 25 cm) plexiglas tank based on interruption of photoelectric cells. Impulses from the photocells trigger the pens of a 6-channel event recorder. During its operation the apparatus is covered with an opaque plastic sheet. Lobster behavior was such that the animals always settled in one of the chamber ends and the test material could be injected at the far end. The lobsters responded to a variety of test materials.