- A Unit to Continuously Monitor Dissolved Oxygen and
Temperature at User-Selected Depths and Locations in Culture
Ponds
Philip R. Pearson, Bartholomew W. Green
A 2004 field study conducted during actual channel catfish
Ictalurus punctatus harvests and a small-scale research
study conducted in 2005, required continuous measurement of
dissolved oxygen concentration and temperature at two depths in
the water column. The on-farm study required data collection in
grading nets loaded with high densities of channel catfish,
whereas the small-scale study was conducted in 0.1-acre channel
catfish research ponds. Commercially available monitoring units
did not meet study requirements, so a free-floating data
collection unit comprised of a combination of state-of-the-art
sensor and datalogger technology and readily available
materials was developed. The data collection units proved
durable under conditions existing in both loaded grading nets
and in small research ponds.
- A Calculator for Estimating Oxygen Consumption By
Channel Catfish
Philip R. Pearson, Rachel V. Beecham
A review of scientific literature concerning channel catfish
Ictalurus punctatus respiration resulted in development of
a Microsoft Excel© spreadsheet for estimating the volume of
oxygen consumed by a given channel catfish biomass. Channel
catfish farmers and live haulers using diffused oxygen aeration
systems can use computed estimates of oxygen consumption as a
guide for setting flow rates for diffusers placed in grading
nets and haul tanks, respectfully. Entry of eight variables
into the spreadsheet provides estimates of oxygen gas
consumption with respect to time and biomass, the liquid oxygen
equivalent of that volume, liquid oxygen expense, and the ratio
of liquid oxygen expense to gross revenue.
- Impact of Horizontal or Vertical Circulation on Water
Quality, Plankton, and Catfish Production
Bartholomew Green, Peter Perschbacher, Kevin Schrader
The present study was conducted to evaluate the effect of a
horizontal discharge or an up-welling vertical discharge
circulator on water quality, plankton and channel catfish
production. Twelve 0.25-acre earthen ponds were used for this
completely randomized design study. Four ponds each were
equipped with a low-revolutions-per-minute (approximately 6
RPM) horizontal discharge circulator or an up-welling vertical
discharge circulator. Circulators operated continuously. All
ponds were equipped with an electric paddlewheel aerator (0.373
kW) that was activated when pond DO concentration was 4.0 mg/L
or less. Control ponds were equipped with only the paddlewheel
aerator. Ponds were stocked with stocker catfish at 4,567
lb/acre; mean initial stocker weight was 0.72 lb/fish.
Fingerling catfish (32.8 lb/1,000) were understocked at
6,000/acre. Ponds were stocked in late January to early
February. Fish were fed a 32% protein floating extruded feed
daily to apparent satiation. Ponds were harvested during the
last week of October. Green algae predominated in all
treatments ponds through mid-June, after which blue-green algae
predominated until harvest. Chlorophyll a concentrations were
similar among treatments, and averaged 240.3, 197.2, and 194.7
mg/m3 for the control, horizontal and vertical circulation
treatments, respectively. Off-flavor algae were present in
treatment ponds from mid-July through early September. No
treatment differences were detected among water quality
variable means. However, temperature and dissolved oxygen
concentration profiles were uniform to the 30-in depth in
circulated ponds. Thus, excess photosynthetically produced
dissolved oxygen was retained in circulated ponds. Net catfish
yield was similar among treatments and averaged 7,484 lb/acre,
of which 86% exceeded 1.25 lb average weight. Mean individual
weight at harvest among treatments was 1.99 lb. At harvest,
fish from all treatments were classified as being off-flavor.
Pond circulation impacted positively pond temperature and
dissolved oxygen, but had no significant impact on fish
production, plankton, or water quality variables.
- Effect of Stocking Rate on Growth, Survival and Yield of
Channel x Blue Hybrid Catfish in a Microbially Based Production
System
Bartholomew Green
The effect of stocking rate on growth, survival, and yield of
channel x blue hybrid catfish reared in a microbially based
production system was evaluated in this study. Nine 450 ft2 x
30” deep, HDPE-lined divided raceways were used for this study.
Each raceway was equipped with a ½-hp electric paddlewheel
aerator that operated continuously. Stocker channel x blue
hybrid catfish (186 lb/1,000) were stocked into raceways at 25,
50, 75, 100, 125, 150, 175, 200, and 225 fish/raceway. Fish
were fed a 32% protein feed. Additional carbon, as wheat flour,
was added daily to each raceway based on feed additions
beginning in July. Water quality variables were measured at
weekly intervals. Raceways were harvested after 188 days. At
harvest, mean individual fish weight ranged from 0.74 – 1.19
lb/fish. Mean individual fish weight decreased linearly with
increased stocking rate. Fish survival ranged from 60 – 80%,
and averaged 70%. The biomass of fish at harvest increased
linearly from 0.01 – 0.08 lb/ft3. Dense phytoplankton blooms
formed in the raceways as indicated by chlorophyll a
concentrations ranged from 1,000 – 4,000 mg/m3. Microbial
action maintained low concentrations of total ammonia nitrogen
and nitrite nitrogen in all raceways, and resulted in
concentrations of nitrate nitrogen that ranged from 20 – 90
mg/L NO3-N at the end of the experiment. The results of this
study indicate that hybrid catfish can be grown in a
microbially based production system in raceways. Mean weight at
harvest was inversely proportional to stocking rate, while
final biomass was directly proportional to stocking rate.
Further testing and refinement of this system is on-going.
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