SCREENING AND EVALUATION OF POLYMERS AS FLOCCULATION AIDS
FOR THE TREATMENT OF AQUACULTURAL EFFLUENTS
James M. Ebeling, Kata L. Rishel, Philip L. Sibrell-2005
Aquacultural Engineering 33 (4): 235-249
Abstract:
As environmental regulations become more stringent, environmentally sound waste
management and disposal are becoming increasingly more important in all aquaculture
operations. One of the primary water quality parameters of concern is the suspended
solids concentration in the discharged effluent. For example, EPA initially
considered the establishment of numerical limitations for only one single pollutant:
total suspended solids (TSS). For recirculation systems, the proposed TSS limitations
would have applied to solids polishing or secondary solids removal technology.
The new rules and regulations from EPA (August 23, 2004) require only qualitative
TSS limits, in the form of solids control best management practices (BMP), allowing
individual regional and site specific conditions to be addressed by existing
state or regional programs through NPDES permits. In recirculation systems,
microscreen filters are commonly used to remove the suspended solids from the
process water. Further concentration of suspended solids from the backwash water
of the microscreen filter could significantly reduce quantity of discharge water.
And in some cases, the backwash water from microscreen filters needs to be further
concentrated to minimize storage volume during over wintering for land disposal
or other final disposal options. In addition, this may be required to meet local,
state, and regional discharge water quality. The objective of this research
was an initial screening of several commercially available polymers routinely
used as coagulation–flocculation aids in the drinking and wastewater treatment
industry and determination of their effectiveness for the treatment of aquaculture
wastewater. Based on the results of the initial screening, a further evaluation
of six polymers was conducted to estimate the optimum polymer dosage for flocculation
of aquaculture microscreen effluent and overall solids removal efficiency. Results
of these evaluations show TSS removal was close to 99% via settling, with final
TSS values ranging from as low as 10–17 mg/L. Although not intended to
be used for reactive phosphorus (RP) removal, RP was reduced by 92–95%
by removing most of the TSS in the wastewater to approximately 1 mg/L–P.
Dosage requirements were fairly uniform, requiring between 15 and 20 mg/L of
polymer. Using these dosages, estimated costs range from $4.38 to $13.08 per
metric tonne of feed.
(The Conservation Fund Freshwater Institute, 1098 Turner Road, Shepherdstown,
WV 25443, USA; email of J. Ebeling:
j.ebeling@freshwaterinstitute.org)
MEASUREMENT OF 5-DAY BIOCHEMICAL OXYGEN DEMAND WITHOUT SAMPLE DILUTION OR BACTERIAL
AND NUTRIENT ENHANCEMENT
Jiang Xinglong, Claude E. Boyd-2005
Aquacultural Engineering 33 (4): 250-257
Abstract:
A direct method for measuring the 5-day biochemical oxygen demand (BOD5) of
aquaculture samples that does not require sample dilution or bacterial and nutrient
enrichment was evaluated. The regression coefficient (R2) between the direct
method and the standard method for the analyses of 32 samples from catfish ponds
was 0.996. The slope of the regression line did not differ from 1.0 or the Y-intercept
from 0.0 at P = 0.05. Thus, there was almost perfect agreement between the two
methods. The control limits (three standard deviations of the mean) for a standard
solution containing 15 mg/L each of glutamic acid and glucose were 17.4 and
20.4 mg/L. The precision of the two methods, based on eight replicate analyses
of four pond water samples did not differ at P = 0.05.
(Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China;
email of C. Boyd:
ceboyd@acesag.auburn.edu)
DEVELOPMENT OF CRYOPRESERVATION PROCEDURES FOR SEMEN OF PACIFIC BLUEFIN TUNA
THUNNUS ORIENTALIS
Han-Hwang Gwo, Ting-Sheng Weng, Lee-Shing Fan, Yan-Horn Lee-2005
Aquaculture 249 (1-4): 205-211
Abstract:
A method for cryopreservation of Pacific bluefin tuna semen, on board ships,
was developed in the current study. Semen was collected by squeezing the abdomen
of long-line fished tuna. The effect of following variables was tested on post-thaw
sperm cell motility: two extender solutions (1% NaCl or 1% glucose), three cryoprotectant
compounds (glycerol, DMSO and methanol) at three different concentrations (10,
20 or 30%), the duration of equilibration time (5, 10 or 20 min) in the cryoprotectant
solutions and two freezing procedures (immediate immersion in liquid nitrogen
or by a two-step freezing procedure). Samples were stored for 7, 30 or 60 days
in liquid nitrogen. Post-thaw motility was found only in samples suspended in
1% NaCl (275–290 mOsm/kg) and in those subjected to the two-step freezing
procedure. Motility was observed only in 11 of the tested treatment groups and
no clear trend was found for the equilibration time in the different cryoprotectant
solutions. Sperm cells remained motile for about 480 s after thawing, with those
suspended in glycerol showing a distinctive specific pattern. Cells suspended
in glycerol showed a gradual increase in motility during the first 20 s after
thawing and motility was reduced later after 480 s. The duration of storage
in liquid nitrogen did not affect post-thaw motility of sperm cells. The methods
suggested for cryopreservation of Pacific bluefin tuna sperm cells based on
sperm cell motility, await confirmation by successful fertilization of eggs,
whenever they will become available.
(Department of Leisure Planning, National Formosa University, 64 Wen-Hua Rd.,
Huwei, Yunlin, 632, Taiwan; email of Yan-Horn Lee:
ghh0426123@yahoo.com.tw)
RELATIVE IMPORTANCE OF FAMILY, SITE, AND FIELD PLACEMENT TIMING ON SURVIVAL,
GROWTH, AND YIELD OF HATCHERY-PRODUCED PACIFIC OYSTER SPAT (CRASSOSTREA GIGAS)
Lionel Dégremont, Edouard Bédier, Patrick Soletchnik, Michel Ropert,
Arnaud Huvet, Jeanne Moal, Jean-Francois Samain, Pierre Boudry-2005
Aquaculture 249 (1-4) : 213-229
Abstract:
Summer mortality has been reported in the Pacific oyster, Crassostrea gigas,
for many years in different parts of the world. The causes of this phenomenon
are complex. The multidisciplinary program “MOREST”, coordinated
by IFREMER, was initiated to understand the causes of summer mortality of Crassostrea
gigas juveniles in France and to reduce its impact on oyster production. Within
this program, three successive groups of bi-parental families were bred in a
hatchery in 2001 and placed in the field during summer in three sites (Ronce,
Rivière d'Auray, and Baie des Veys). This paper reports the relative
importance of family, site and field placement timing for three characters of
major importance for oyster production: survival, growth, and yield. At the
end of the summer period, significant differences for the three characters were
observed among sites and families for each group. Family effect was the largest
variance component for survival, representing 46% of the total. Variance component
analysis revealed that variation in yield among families depended either on
survival or on growth according to the site. Significant family × environment
interactions were observed for yield and survival but not for growth. No difference
in survival was found among groups in the three sites at the end of the experiment,
but a critical period of mortality was identified from late July until early
September. The influence of environmental conditions, notably on reproductive
allocation and its relationship with the studied traits, is discussed.
(IFREMER — Laboratoire de Génétique et Pathologie —
17390 La Tremblade, France; email of P. Boudry:
pierre.boudry@ifremer.fr)
ADVANCES IN REARING COBIA RACHYCENTRON CANADUM LARVAE IN RECIRCULATING AQUACULTURE
SYSTEMS: LIVE PREY ENRICHMENT AND GREENWATER CULTURE
Cynthia K. Faulk, G. Joan Holt-2005
Aquaculture 249 (1-4): 231-243
Abstract:
Cobia Rachycentron canadum is a relatively hardy species which exhibits high
rates of growth during the larval and juvenile periods. Currently, this species
is considered to be a good candidate for commercial production in recirculating
aquaculture systems. However, little information is available regarding the
nutritional requirements of cobia larvae in such systems, and this information
is required to advance commercial technologies for the successful production
of cobia fingerlings. Experiments were conducted to examine the effects of enriching
rotifers and Artemia with live algae or commercial preparations on the growth
and survival of cobia R. canadum larvae and to evaluate the benefits of adding
live algae to the systems. Prey items were enriched with live Isochrysis galbana,
live Nannochloris oculata, Algamac 2000, Algamac 2000 supplemented with 10%
or 20% Aquagrow arachidonic acid, or Algamac 3050. In addition, larvae fed prey
enriched with Algamac 2000 were reared in the presence of live I. galbana (
40,000 cells ml- 1) or N. oculata ( 80,000 cells ml- 1). Significant differences
in the fatty acid composition of the rotifers and Artemia were found among treatments.
Generally, prey enriched with the commercial preparations contained higher levels
of highly unsaturated fatty acids than those enriched with live algae. Furthermore,
a positive correlation was found between dietary docosahexaenoic acid (DHA)
and the amount of DHA measured in the whole body tissues of 16-day-old larvae.
Larval growth (measured as standard length) and survival of 16-day-old larvae
were significantly higher (P < 0.05) when larvae were fed prey enriched with
the commercial preparations (14.7–15.2 mm; 12.0–15.6%) compared
to N. oculata (11.8 mm; 4.4%). However, when larvae were reared on N. oculata
enriched rotifers and subsequently fed Algamac 2000 enriched Artemia there were
no significant differences in growth or survival compared to larvae which were
fed both rotifers and Artemia enriched with Algamac 2000. This suggests that
the enrichment of rotifers may be less important than the enrichment of Artemia.
No significant differences in growth or survival were found when larvae were
fed prey enriched with live I. galbana (13.5 mm; 8.2%) or commercial preparations
(12.4–12.6 mm; 12.9%). However, the presence of live algae (I. galbana
or N. oculata) in the rearing tanks significantly improved larval survival to
23.3% and 24.7%, respectively. The results of this study suggest that enriching
rotifers and Artemia with live I. galbana or commercial preparations such as
Algamac 2000 and 3050 in conjunction with greenwater culture systems improves
the growth and survival of cobia larvae in recirculating aquaculture systems.
(University of Texas at Austin Marine Science Institute, Fisheries and Mariculture
Laboratory, 750 Channel View Drive, Port Aransas, TX 78373, USA; email of C.
Faulk:
cfaulk@utmsi.utexas.edu)
INFLUENCE OF TEMPERATURE ON LARVAL DEVELOPMENT OF PACIFIC BROWN SHRIMP FARFANTEPENAEUS
CALIFORNIENSIS
Humberto Villarreal , Alfredo Hernandez-Llamas-2005
Aquaculture 249 (1-4): 257-263
Abstract:
The influence of water temperature on larval development of Pacific brown shrimp
Farfantepenaeus californiensis was studied under laboratory conditions. As temperature
increased from 22 to 30 °C, higher growth rates were recorded, as indicated
by a significant linear relationship between variables. In general, the duration
of each larval stage was inversely related to temperature, and the time to reach
postlarval stage decreased from 18 to 10 days as temperature increased from
22 to 30 °C. Size of postlarvae ranged from 5.47 to 6.61 mm, and a quadratic
equation showed a significant fit to size data in relation to temperature. Maximum
size was estimated at 25.8 °C. A significant result was also obtained when
fitting a quadratic equation to survival data, ranging from 41.6 to 73.5%. Maximum
survival was estimated at 26.6 °C. It is concluded that 26 °C is optimal
for rearing brown shrimp larvae. The implications of high sensitivity of the
larval stages to changes in temperature for cultivated and natural stocks are
addressed.
(Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Mar Bermejo
195, La Paz, B.C.S. 23090, México; email of A. Hernandez-Llamas:
ahllamas04@cibnor.mx)
DEVELOPMENT OF AN OPTIMAL MICROALGAL DIET FOR THE CULTURE OF THE CALANOID COPEPOD
ACARTIA SINJIENSIS: EFFECT OF ALGAL SPECIES AND FEED CONCENTRATION ON COPEPOD
DEVELOPMENT
Richard M. Knuckey, Gale L. Semmens, Robert J. Mayer, Michael A. Rimmer-2005
Aquaculture 249 (1-4): 339-351
Abstract:
Of the calanoid copepods, species of the genus Acartia are most commonly used
for larval diets of tropical marine finfish. It is sourced from adventitious
harvesting of wild populations or less frequently, cultured specifically as
a live feed. However, little work is published on optimising diets for the aquaculture
of copepods. In this study, A. sinjiensis was cultured on a range of mono- and
binary algal diets and the effect on development assessed. There were significant
differences in the rate of copepod development between the mono-algal diets.
Rhodomonas was confirmed as an excellent algal diet for Acartia, but it is often
unpredictable in mass culture. The cryptophyte, Cryptomonad sp. (CS-412) was
shown to support an equally rapid development rate with the advantage of being
more stable in mass culture. The algal feed concentration for maximal copepod
development rate was dependent on the algal feed species. For the cryptophytes
Rhodomonas sp. or Cryptomonad sp., 1.13 µg AFDW ml- 1 was the minimal
feed concentration required to support maximal copepod development at 28 °C.
Mono-algal diets of the prymnesiophyte Isochrysis sp. (T.ISO) or Pavlova salina
supported a lower level of copepod development than an equivalent biomass of
either cryptophyte. Also, a higher feed concentration was required to achieve
these lower development rates: 2.02 and 1.86 µg AFDW ml- 1 for Isochrysis
sp. (T.ISO) and P. salina, respectively. Copepod nauplii fed the prasinophyte
Tetraselmis sp., developed as fast as those fed an equal biomass of cryptophyte.
However, development did not proceed beyond copepodite stage C1. Although survival
was high, almost all of these C1 copepodites exhibited signs of a nutritional
irregularity. The eyespot was frequently completely absent, greatly reduced
in size or fragmented and setae were twisted. For rapid development, a mono-algal
diet of Cryptomonad sp. could be used for the culture of A. sinjiensis. However,
inclusion of a lipid-rich prymnesiophyte is likely to be beneficial to maximise
egg production, a lipid dependent process.
(Department of Primary Industries and Fisheries, Northern Fisheries Centre,
PO Box 5396, Cairns 4870, Queensland, Australia; email of R. Knuckey:
Richard.Knuckey@dpi.qld.gov.au)
THE EFFECT OF GRADED CONCENTRATIONS OF DIETARY DHA ON GROWTH, SURVIVAL AND TISSUE
FATTY ACID PROFILE OF SENEGAL SOLE (SOLEA SENEGALENSIS) LARVAE DURING THE ARTEMIA
FEEDING PERIOD
Mireia Villalta, Alicia Estévez, Matthew P. Bransden, J. Gordon Bell-2005
Aquaculture 249 (1-4) : 353-365
Abstract:
We examined the effect of dietary docosahexaenoic acid (22:6n-3, DHA) on growth,
survival, pigmentation and fatty acid composition of Senegal sole larvae using
a dose–response design. From 3 to 35 days post-hatch (dph), larvae were
fed live food (rotifers from 3 to 9 dph, Artemia nauplii from 5 to 35 dph) that
had been enriched using one of four experimental emulsions containing four graduated
concentrations of DHA and constant arachidonic acid (20:4n-6, ARA) and eicosapentaenoic
acid (20:5n-3, EPA). Final proportions of DHA in the enriched Artemia nauplii
were described as ‘nil’ (DHA-N, 0.0% total fatty acids, TFA), ‘low’
(DHA-L, 4.4% TFA), ‘medium’ (DHA-M, 7.7% TFA) or ‘high’
(DHA-H, 14.7% TFA). Significant differences among dietary treatments in larval
length occurred at 20, 30 and 36 dph, and in dry weight at 20 and 30 dph, although
there was no significant relationship between dietary DHA and growth. The stage
of eye migration at 20 dph was significantly affected by dietary levels of DHA.
No significant differences in survival were obtained. Tissue fatty acid concentrations
reflected the corresponding dietary composition. Fish fed DHA-M and -H enriched
nauplii tended to accumulate less lipid, mainly oleic acid (OA), in the carcass
that might have caused the lower growth in length observed in DHA-H fish. We
hypothesise that negligible amounts of dietary DHA required for normal development
in Senegal sole larvae relate to a predominance of EPA rather than DHA in the
benthic fauna which this flatfish consumes in the wild post-settlement.
(Centro de Acuicultura-IRTA and Centro de Referencia en Acuicultura, Generalitat
de Cataluña, Ctra. Poble Nou Km 6, 43540 San Carlos de la Rápita,
Tarragona, Spain; email of A. Estevez:
alicia.estevez@irta.es)
LARVAL DEVELOPMENT AND METAMORPHOSIS IN THE SEA URCHIN LOXECHINUS ALBUS (ECHINODERMATA:
ECHINOIDEA): EFFECTS OF DIET TYPE AND FEEDING FREQUENCY
P.F. Cárcamo A.I. Candia, O.R. Chaparro-2005
Aquaculture 249 (1-4) : 375-386
Abstract:
Techniques presently used in the mass production of larvae and juveniles of
the sea urchin Loxechinus albus require optimization of methods related to their
feeding. For this reason, the present research evaluated the effects of the
type of diet and the frequency of feeding on morphological development and larval
survival, as well as on the success of larval metamorphosis. The effect of the
diet type was assessed in an experiment with three microalgal diets (Chaetoceros
calcitrans = C, C. calcitrans and Isochrysis galbana = CI and C. calcitrans,
I. galbana, and Tetraselmis suecica = CIT). The effect of feeding frequency
was assessed in a second experiment with three feeding regimes (daily feeding
at normal ration—DN, feeding every second day at normal ration—SN,
and feeding every second day at double ration—SD). Total larval growth
and the growth of larval structures were affected by the type of food and by
the feeding frequency. Larvae fed diets C and CI showed no significant difference
in survival of competent larvae (mean ± SD: 48.8 ± 16.9 and 58.3
± 14.4%) and in percent metamorphosis (59.3 ± 13.5 and 56.7 ±
10.3%). The size of the postmetamorphic sea urchins was significantly greater
for the CI treatment (419.6 ± 35.4 µm) than for the C treatment
(403.3 ± 31.6 µm). Larvae fed with CIT diet did not reach competence.
Larvae fed at the DN regime reached competence in significantly greater numbers
(46.0 ± 3.7%) than those fed with the SN regime (29.8 ± 5.5%)
or the SD regime (31.4 ± 7.5%). There was no significant difference in
the numbers of larvae achieving metamorphosis between regimes DN (49.3 ±
8.6%) and SD (57.3 ± 9.4%), but both means were greater than that of
the SN regime (2.7 ± 2.1%). The postmetamorphic urchins from regime DN
reached the largest size (413.9 ± 39.5 µm). The results suggest
that daily larval feeding which includes a mixed diet of larger algal cells,
including C. calcitrans but excluding T. suecica, may produce better results
for large-scale production of competent larvae and juveniles of L. albus.
(División de Investigación en Acuicultura, Instituto de Fomento
Pesquero, Balmaceda 252, Puerto Montt, Chile; email of P. Carcamo:
pcarcamo@ifop.cl)
DIETARY L-METHIONINE REQUIREMENT OF JUVENILE GROUPER EPINEPHELUS COIOIDES AT
A CONSTANT DIETARY CYSTINE LEVEL
Zhi Luo, Yong-jian Liu, Kang-sen Mai, Li-xia Tian, Hui-jun Yang, Xiao-ying Tan,
Dong-hui Liu-2005
Aquaculture 249 (1-4): 409-418
Abstract :
The present experiment was conducted to determine the methionine requirement
and the effect of dietary methionine levels on growth, feed utilization, body
composition, haematological and morphometrical parameters in juvenile grouper.
Diet 1 with fish meal as the sole protein source was used as a reference. Diets
2–7 were formulated to contain 48% crude protein and supplemented with
graded concentrations of l-methionine, resulting in six levels of dietary methionine
(0.55–1.81% of dry matter) at a constant dietary cystine level of 0.26%.
Fish (initial weight of 13.25 ± 0.19 g, mean ± S.D.) were reared
in twenty-one 500-l circular fibreglass tanks provided with flow-through seawater
at 28–30.5 °C and salinity of 24–28 mg/l for 8 weeks. Fish fed
the reference diet had significantly higher weight gain (WG), specific growth
rate (SGR), feed utilization efficiency, protein and lipid contents of whole
body, plasma protein and cholesterol concentrations (P < 0.05). Among other
treatments fed the diets containing CAAs, increasing dietary methionine up to
1.34% increased growth performance and feed utilization, whole-body protein
and lipid contents, condition factor (CF), viscerosomatic index (VSI) and intraperitoneal
fat ratio (IPR), beyond which they remained nearly unchanged. Plasma protein
concentration showed no significant differences for fish fed the diet containing
more than 1.11% methionine. Triacylglycerol increased with increasing dietary
methionine levels, but showed a relatively lower value for fish fed the 1.59%
methionine diet. Plasma glucose could not be related to dietary treatments.
Cholesterol was the highest for fish fed the 1.34% methionine diet but showed
no significant difference among other treatments. Fish fed higher-methionine
diets exhibited relatively higher essential amino acid (EAA) contents in muscle
than fish fed the lower methionine diet (P < 0.05). Broken-line regression
analysis of WG against dietary methionine level indicated that optimal dietary
methionine requirement for juvenile grouper was 1.31% of the diet (corresponding
to 2.73% of dietary protein on a dry weight basis).
(Nutrition Laboratory, Institute of Aquatic Economic Animals, School of Life
Sciences, Sun Yat-sen University, Guangzhou 510275, PR China; email of Zhi Luo:
luozhi99@yahoo.com.cn)
SURVIVAL, GROWTH AND FEEDING EFFICIENCY OF LITOPENAEUS VANNAMEI PROTOZOEA LARVAE
FED DIFFERENT RATIONS OF THE DIATOM CHAETOCEROS MUELLERI
Pablo Piña, Mario Nieves, Luis Ramos-Brito, Cesar O. Chavira-Ortega,
Domenico Voltolina-2005
Aquaculture 249 (1-4) : 431-437
Abstract:
The survival, development and growth of Litopenaeus vannamei protozoea (PZ)
larvae were evaluated in three experiments during which they were fed five different
rations of the diatom Chaetoceros muelleri, from emerging PZ I larvae until
the day of change to mysis I. The total amount of food and energy supplied in
5 days to each larva ranged from 85.5 to 223.2 µg larva- 1 (ash-free dry
weight) and between 2.25 and 5.88 J larva- 1. After 2 days, the development
index (DI) showed that some of the larvae fed the highest ration had reached
the stage of PZ III. At the end of the experiment the mean DI ranged from 2.9
± 0.2 to 3.2 ± 0.3 and the differences among treatments were not
significant. The mean percentages of survival ranged from 35.8% to 51.7% and
were not statistically different, but total length was progressively higher
with increasing ration. The final values were 1.91 ± 0.54, 2.10 ±
0.53; 2.34 ± 0.36; 2.45 ± 0.37 and 2.55 ± 0.42 mm and were
all statistically different with the exception of treatment 4, that was intermediate
between treatments 3 and 5. However, the highest final organic weight (26.0
± 1.7 µg larva- 1) was treatment 4, which was different from the
values obtained with the two lower rations. Treatments 3 and 5 had intermediate
values. The percentages of the food ingested did not vary with the rations supplied
or with the age of the larvae and ranged from 74% to 86%. Food ingestion (Fi)
was a function of the food supplied (Fs), according to the equation Fi = 0.848Fs
- 4.025 (R2 = 0.992; P < 0.001). Using the amount of food supplied and ingested
with each feeding regime and the respective organic weight gains, it was calculated
that the percentages of Fs and Fi used for body growth were 14.4% and 17.9%
with the lowest ration and 6.9% and 8.3% with the highest, whereas the three
intermediate rations gave similar efficiencies (9.8% to 10.2% of Fs and 11.8%
to 12.5% of Fi). However, the weight and energy gains obtained with the highest
food utilization efficiency were lower than those obtained with the higher rations,
indicating that cautious overfeeding is a more convenient alternative for L.
vannamei PZ culture.
(Universidad Autónoma de Sinaloa, Facultad de Ciencias del Mar, Paseo
Claussen s/n, Mazatlán, Sinaloa, Mexico; email of Pablo Piña:
microalgas@mzt.megared.net.mx)
SPERM CHARACTERISTICS AND FERTILIZATION SUCCESS OF MASCULINIZED COHO SALMON
(ONCORHYNCHUS KISUTCH)
J.L. Fitzpatrick, J.C. Henry, N.R. Liley, R.H. Devlin-2005
Aquaculture 249 (1-4) : 459-468
Abstract:
Endocrine technologies and sex modification of fish stocks are playing an increasingly
important role in commercial aquaculture production. The characteristics and
fertilization success of sperm from masculinized coho salmon (Oncorhynchus kisutch)
were examined and compared to that of regular coho salmon sperm. Sperm from
masculinized XX males was stripped, or when the efferent ducts were not developed
the semen was collected from the testis, and compared with semen from normal
XY males. Stripped masculinized genetic females exhibited similar measures of
sperm velocity and sperm density as normal male coho salmon, with both of these
groups differing significantly from testicular sperm from masculinized females.
In commercial fertilization trials, fertilization success was not altered by
the dichotomy observed between testicular and stripped milt from masculinized
females. Treatment with leutenizing hormone releasing analogues had no effect
on sperm motility, density, or fertility. Much of the difference in sperm characteristics
can be attributed to the difference between stripped sperm and testicular sperm.
(Department of Zoology, The University of British Columbia, 6270 University
Boulevard, Vancouver, Canada, B.C. V6T 1Z4; email of J.L. Fitzpatrick:
fitzpajl@mcmaster.ca)
SPERMATOZOAL ULTRASTRUCTURE OF DIPLOID AND TETRAPLOID PACIFIC OYSTERS
Qiaoxiang Dong, Changjiang Huang, Terrence R. Tiersch-2005
Aquaculture 249 (1-4): 487-496
Abstract:
Spermatozoal ultrastructure of tetraploid Pacific oysters, Crassostrea gigas,
was examined by light and electron microscopy and compared to that of diploid
Pacific oysters. Ultrastructure of sperm from tetraploids was compositionally
similar to diploids except for overall size and the number of mitochondria.
Instead of the four mitochondria always found in sperm from diploid oysters,
44% of sperm from tetraploid oysters had four mitochondria, 53% had five, and
3% had six. The linear dimensions of sperm components such as acrosome height
and width, sperm head length and width, mitochondrial height, length of the
main piece and end piece of flagellum, and total length of flagellum in tetraploids
were approximately 1.25 times larger than corresponding measurements in diploids,
which corresponds to a doubled volume in sperm of tetraploids compared to that
of diploids. Tetraploid males produced half the number of sperm (2.7 ±
0.5 × 1010) g- 1 of gonad wet weight compared to diploid males. Despite
the increased sperm sizes in tetraploids, the ratios of the sperm head length
to head width, and sperm head length to flagellum length were the same for both
ploidy levels for fixed and live samples. The implications of these findings
on susceptibility of sperm from diploid and tetraploid oysters to damage from
cryopreservation are discussed.
(Aquaculture Research Station, Louisiana Agricultural Experiment Station, Louisiana
State University Agricultural Center, Baton Rouge, Louisiana 70803, USA; email
of T. Tiersch:
ttiersch@agctr.lsu.edu)
THE EFFECT OF HEAT AND COLD EXPOSURE ON HSP70 EXPRESSION AND DEVELOPMENT OF
DEFORMITIES DURING EMBRYOGENESIS OF ATLANTIC SALMON (SALMO SALAR)
Harald Takle, Grete Baeverfjord, Merete Lunde, Kari Kolstad, Øivind Andersen-2005
Aquaculture 249 (1-4): 515-524
Abstract :
Temperature stress is recognized as a teratogenic factor that induces deformities
during the embryonic development of teleosts. In order to further elaborate
the mechanisms involved, Atlantic salmon (Salmo salar) embryos were heat (16
°C) and cold (1 °C) shocked at eight and four different embryonic stages,
respectively, during the period from gastrulation until the completion of somitogenesis.
Additionally, embryos were subjected to a long-term heat exposure at 12 °C
from the 1st until the 20th somite stage. Real-time RT-PCR results showed that
the HSP70 mRNA expression was dependent on the stage of development. Whereas
temperature shock was found to induce HSP70 mRNA up-regulation at the gastrula
stage, the 9th, the 15th, the 20th and the 45th somite stage, the additional
three investigated stages showed no up-regulation. The highest HSP70 expression
levels were induced at the 45th somite stage as shown by a 12- and 4-fold increase
after heat and cold shock, respectively. Embryos subjected to the prolonged
heat exposure showed a stronger HSP70 expression than embryos that were given
a 1-h heat shock. Intriguingly, a high incidence (17%) of situs inversus of
abdominal organs was found in fry subjected to the long-term exposure, supporting
that early somitogenesis is an important period of left–right determination
in teleosts. In general, the 1-h temperature shock was not sufficient to induce
high frequencies of deformities. Though, a 14% incidence of vertebral deformities
was observed both at the 45th somite stage and at the completion of somitogenesis
after cold shock. The results provide new insight regarding the tolerance of
high and low temperature stress in Atlantic salmon embryos.
(AKVAFORSK (Institute of Aquaculture Research), Norwegian University of Life
Sciences P.O. Box 5010, N-1432 Ås, Norway; email of H. Takle:
harald.takle@akvaforsk.no)
ARTIFICIAL MATURATION AND REPRODUCTION OF EUROPEAN SILVER EEL: DEVELOPMENT OF
OOCYTES DURING FINAL MATURATION
A.P. Palstra, , E.G.H. Cohen, P.R.W. Niemantsverdriet, V.J.T. van Ginneken and
G.E.E.J.M. van den Thillart-2005
Aquaculture 249 (1-4): 533-547
Abstract:
Attempts on artificial maturation of European eel (Anguilla anguilla) have largely
been unsuccessful. The moment of stimulation of final maturation and ovulation
is mainly based on weight increase related to the hydration response of the
oocytes, which, in the European eel, is irregular. In contrast to Japanese eel,
European eels show wide individual variability and much slower response to hormonal
stimulation. In this study, the oocyte development of wild European silver eels
was followed during final maturation. We describe 7 developmental stages based
on 6 parameters: transparency, position and visibility of the nucleus, diameter
of the oocyte, and diameter and number of oil droplets. Together, these parameters
describe unidirectional changes from immature to over-ripe eggs. The developmental
status of the gonads can thus be determined from biopsies. Of 23 female eels,
14 ovulated and were stripped, and 9 gave eggs that could be fertilised. Oocytes
mature asynchronously, but this seems to be an artefact since fertility dropped
with every new generation. As the timing of ovulation is crucial for fertility
of the eggs, our developmental index of oocytes may result in more successful
maturation protocols.
(Integrative Zoology, Institute of Biology Leiden, van der Klaauw Laboratories,
P.O. Box 9511, Kaiserstraat 63, 2300 RA Leiden, The Netherlands; email of A.
Palstra:
Palstra@rulsfb.leidenuniv.nl)
EFFECTS OF TANK COLOUR ON LARVAL SURVIVAL AND DEVELOPMENT OF MUD CRAB SCYLLA
SERRATA (FORSKÅL)
Abed Golam Rabbani, Chaoshu Zeng-2005
Aquaculture Research 36 (11): 1112-1119
Abstract:
Hatchery culture of mud crabs has not yet achieved commercial viability despite
decades of research efforts. Further research is therefore needed to better
understand larval culture requirements of the crab. Based on anecdotal observations,
an experiment was carried out to test whether the background colour of the culture
vessel affected larval culture success. Newly hatched larvae of Scylla serrata
were reared in culture vessels of five colours, i.e., black, dark green, maroon,
sky blue and white. Larval survival and development were monitored daily until
all of them either moulted to the first crab stage or died. The results showed
clear effects of background colour on larval survival. A general tendency of
higher larval survival in darker-coloured backgrounds was evident. In particular,
overall zoeal survival for larvae reared in black vessels was significantly
higher than those reared in white ones. Background colour also appeared to affect
larval development. Larvae reared in darker backgrounds generally had shorter
development times and more synchronized moulting. A significant delay in zoeal
development was observed in larvae reared in white vessels. Dark backgrounds
possibly facilitated more efficient feeding, reduced settlement of larvae at
the bottom of the vessels as well as minimized stress. This result appears to
be the first to demonstrate that background colour can significantly affect
larval survival and development of a crustacean species.
(Tropical Crustacean Aquaculture Research Group, School of Marine Biology and
Aquaculture, James Cook University, Townsville, Queensland 4811, Australia;
email of Chaoshu Zeng:
chaoshu.zeng@jcu.edu.au)
MATURATION DIET BASED ON FATTY ACID CONTENT FOR MALE PENAEUS MONODON (FABRICIUS)
BROODSTOCK
Oraporn Meunpol, Panadda Meejing, Somkiat Piyatiratitivorakul-2005
Aquaculture Research, 36 (12): 1216-1225
Abstract:
The contents of three essential fatty acids, arachidonic acid (AA), eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA), from wild Penaeus monodon broodstock
were evaluated in comparison with natural diet fed P. monodon. Spermatophores
of wild male broodstock contained higher levels of AA than those of artificial
diet fed males. Polychaetes had higher proportion of AA to EPA and DHA at 5.8:5.5:1
in mud polychaetes followed by 12:7:1 in sand polychaetes, while DHA was a preferential
n-3 highly unsaturated fatty acid (HUFA) in squids and fish. The experimental
feed was constructed to simulate the HUFA profile of polychaetes (AA:EPA:DHA
as 5:1:1) and then fed to farmed male black tiger prawn broodstock for 1 month.
The results exhibited comparable reproductive characteristics to wild male suggesting
the possibility of replacing wild males with pond-reared males. Rearing farmed
males in a test unit for a month did not reduce the quality of prawn sperm.
Reproductive performance indices (sperm sac weight, total number of sperm, percentage
of live sperm, percentage of abnormal sperm) from the males of all treatments
were not statistically different except in males fed with pellets. Control (live
feeds) and combined diet provided better reproductive performance in pond-reared
males. Analysis of AA, EPA and DHA in reproductive tissues, hepatopancreas and
muscle of treated animals in each treatment revealed an accumulation of dietary
HUFA into reproductive tissues. No evidence of transfer of HUFA from hepatopancreas
or muscle to spermatophore was found.
(National Center for Genetic Engineering and Biotechnology, 113 Paholyothin
Rd., Pathumthani 12120, Thailand; email of Oraporn Meunpol:
oraporn@biotec.or.th)
SHORT COMMUNICATION: EFFECTS OF TANK COLOUR AND PREY DENSITY ON FIRST FEEDING
OF THE SPOTTED SAND BASS PARALABRAX MACULATOFASCIATUS (STEINDACHNER) LARVAE
Renato Peña, Silvie Dumas, Ana Trasviña, Gerardo García,
Hugo Pliego-Cortéz-2005
Aquaculture Research 36 (12): 1239-1242
(Centro Interdisciplinario de Ciencias Marinas-Instituto Politechnico Nacional,
Unidad Piloto de Maricultivos (CICIMAR-IPN), PO Box 592, La Paz, Baja California
Sur 23000, Mexico; email of R Peña:
blacklarvae@hotmail.com)
EVIDENCE THAT POLYUNSATURATED ALDEHYDES OF DIATOMS ARE REPELLENTS FOR PELAGIC
CRUSTACEAN GRAZERS
Friedrich Jüttner-2005
Aquatic Ecology 39 (3): 271 – 282
Abstract:
Evidence is given that odour compounds of diatoms serve as potential repellents
for crustacean grazers. Novel repellent-test and odour-test apparatus allowed
the determination of repellent activity of diatom derived compounds, activated
by freezing and thawing or mechanical disintegration, and pure compounds, respectively.
Epilithic diatom biofilms when activated, produced odour compounds that were
determined by GC–MS to be polyunsaturated aldehydes (PUA). 2(E),4(Z),7(Z)-Decatrienal
and 2(E),4(Z)-octadienal were the major compounds, and 2(E),4(Z)-heptadienal
was a minor compound. These PUA were each accompanied by small amounts of the
E,E-isomers in positions 2 and 4. 2(E),4(E),7(Z)-Decatrienal was the most active
repellent tested and exhibited a RC50 value (indicating the concentration of
a compound necessary for a 50% reduction of swimming crustaceans in the assay
vial) of 3.5 µM in a defined water column. Quantitative analyses showed
that upon activation diatom biofilms produced large amounts of eicosapentaenoic
acid (EPA) of which only a minor part was degraded to PUA. The major part of
EPA was retained in the cells whilst the major part of PUA was released into
the surrounding water. The data are consistent with the hypothesis that diatoms
damaged by grazers develop free EPA in the cells that is toxic to grazers, and
release PUA into the water that serve as warning signals to grazers. Diatoms
and other phytoplankton species, that have the capacity to form these compounds,
might benefit from such a reaction because the producers live in colonies or
assemblages and the death of one cell liberates a cloud of repellent compounds
into the water which reduces the grazing pressure on the remaining cells. Such
activated defence reactions may help explain food selection and avoidance in
freshwater and marine ecosystems.
(Institute of Plant Biology/Limnological Station, University of Zürich,
Seestrasse 187, CH-8802 Kilchberg, Switzerland; email of Friedrich Jüttner:
juttner@limnol.unizh.ch)
HOW DIVERSE IS AQUATIC BIODIVERSITY RESEARCH?
Aristides Moustakas, Ioannis Karakassis-2005
Aquatic Ecology 39 (3): 367 - 375
Abstract: The use of the term ‘biodiversity’ in the aquatic bibliography
has expanded during the last 10 years at an almost exponential rate. A quantitative
analysis of the bibliography addressing the issue of biodiversity showed that
it is mainly dominated by reviews or policy-oriented articles rather than articles
referring to field data or models. The scientific effort is largely biased in
terms of geographic distribution of the areas studied, country of origin of
the first author and the biota studied. The number of institutions using the
term ‘biodiversity’ in their title also increased dramatically with
time after 1992. The proportion of references using molecular or genetic approaches
to study aquatic biodiversity changed little during the last decade and ranged
between 4 and 10% of the total. Our current perception of the earth’s
aquatic biodiversity has been formed mainly from research carried out in the
developed countries of the Northern Hemisphere. Most publications refer to commercial,
charismatic or large size species, as well as to taxa of well known taxonomy;
this is perhaps more compatible with traditional views of conservation of K-selection
species rather than with concepts linking biodiversity to ecosystem function.
(Ecology & Biodiversity Laboratory, Department of Environmental Engineering,
Technical University of Crete, 73100 Chania, Polytechnioupolis, Greece; email
of Aristides Moustakas:
Aris.m@uni-jena.de)
