Perception of light intensity by Haliotis discus discus based on locomotor activity patterns

ABSTRACT:   An apparatus to measure the locomotor activity of aquatic benthic organisms at variable low light levels was developed and the diurnal behavioral pattern of the abalone Haliotis discus discus was measured at various low light intensities. During the experiment, abalone were exposed to 12 h light–dark cycles of complete darkness, 0 µmol/m²/s throughout the 12 h dark cycle and, during periods I (days 1–8) and III (days 19–26), the 12 h light cycles were set at 10 µmol/m²/s. During period II (days 10–17), abalone were exposed to a light level during the 12 h light cycles of 1 × 10⁻⁵, 1 × 10⁻⁶, 1 × 10⁻⁷ or 1 × 10⁻⁸ µmol/m²/s and the changes in locomotor activity assessed. At daytime levels of 1 × 10⁻⁵ µmol/m²/s, typical behavioral patterns were observed of high locomotory activity during the night-time cycle. However, at lower light intensities, the distinction between day and night activity patterns became less clear and, at intensities lower than 1 × 10⁻⁷ µmol/m²/s, the difference between activity during the light and dark cycles became negligible. Based on this, we conclude that the threshold of light level perception in relation to locomotor activity is approximately 1 × 10⁻⁷ µmol/m²/s. The significance of these results in relation to the entrainment of behavior in abalone is discussed.     

Effects of irradiance of various wavelengths from light-emitting diodes on the growth of the harmful dinoflagellate <Emphasis Type="Italic">Heterocapsa circularisquama</Emphasis> and the diatom <Emphasis Type="Italic">Skeletonema costatum</Emphasis>

ABSTRACT:   We investigated the effects of specific light wavelengths from light-emitting diodes (LEDs) on the growth of the dinoflagellate Heterocapsa circularisquama , which kills bivalves, and the diatom Skeletonema costatum , which is an important food source for bivalves. Growth of H. circularisquama was obviously inhibited at 590 nm and a photon flux density less than 75 μmol quanta/m²/s. However, growth of S. costatum was not suppressed by irradiance from any LEDs tested from near-ultraviolet to near-infrared wavelengths at 75 μmol quanta/m²/s. The growth rate of H. circularisquama in an experimental treatment group with irradiance provided by both cool-white fluorescent lamps (12:12 h L : D cycle) and a 590-nm LED (continuous irradiance) was 0.43/day. In the control group with irradiance provided only by cool-white fluorescent lamps (12:12 h L : D cycle), the growth rate was 0.63/day, indicating that growth of H. circularisquama was suppressed by 590 nm (less than 75 μmol quanta/m²/s) irradiance from the LED and the continuous irradiance. The use of 590-nm LEDs in bivalve culture at irradiance levels less than 75 μmol quanta/m²/s might encourage the growth of the useful diatom S. costatum without stimulating growth of the harmful dinoflagellate H. circularisquama .     

Growth Characteristics of a Neurotoxin-Producing Chloromonad Fibrocapsa japonica (Raphidophyceae)

The effects of temperature, salinity, irradiance and pH on the growth of Fibrocapsa japonica (Raphidophyceae) were examined to determine how environmental factors affect the distribution of this species. Optimal growth was observed at temperatures of 15–25 C, salinities of 25–35 parts per thousand (ppt), irradiances of 60–140 μmol quanta/m² per s and pH between 7.5–8.5. Growth did not occur at temperatures below 10 C or above 30 C nor at salinities below 15 ppt. Fibrocapsa japonica grew when subjected to irradiances of 20–180 μmol quanta/m² per s, and could tolerate a pH range of 6.5–8.5.     

Binding characteristics of the Zn-binding membrane protein from common carp

ABSTRACT:    This study incorporated the 43 kDa Zn-binding membrane protein isolated from common carp into liposome. The specificity and strength of the binding of ⁶⁵Zn to the 43 kDa protein-liposomes, and the binding of the ⁶⁵Zn-labeled 43 kDa protein-liposomes to laminin were studied. It was found that ⁶⁵Zn was bound to the external side of the 43 kDa protein-liposomes. Specific binding of ⁶⁵Zn to the protein-liposomes was detected. The binding parameter of Zn to the protein was found to be: maximum binding site (N_max), 76.7 pmole/µg protein (approx. 3 mole of Zn²⁺/mole); and equilibrium dissociation constant (Kd), 0.19 µM. Of the cations introduced (Ca²⁺, Cd²⁺,Co²⁺, Cr²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺), only Co²⁺ competed significantly with Zn. The protein-liposomes were also found to bind specifically to laminin with a N_max of 1.1 pmole/µg laminin, and Kd of 4.79 µM. No significant protein-liposome binding occurred to other extracellular matrix proteins (fibronectin, fibrinogen or vitronectin). Furthermore, the binding was specifically inhibited by the Arg-Gly-Asp (RGD) peptide or GRGDSPG, while two other analogs (GRGESPG and GRADSPG) were without effect.     

Suspension feeding of the ark shell <Emphasis Type="Italic">Scapharca subcrenata</Emphasis> as a function of environmental and biological variables

ABSTRACT:   To assess the roles of the ark shell Scapharca subcrenata in material cycling in the northern part of Ariake Sound (Mae-no-umi), Japan, filtration of the ark shell fed on small diatoms was examined as a function of environmental and biological variables. The clearance rate ( CR ) specific to the soft-body dry weight ( w ) of the animals (shell length, 8–26 mm) followed a power function of w with an exponent of −0.35. Over the range of 10–20°C, CR increased 2.7 times, and filtration did not occur below a salinity of 14 practical salinity unit. Neither food concentration (10–40 µg/L of chlorophyll- a ) nor weight-specific daily ration (0.5–6%/day in terms of ash-free dry weight) notably affected CR . Using this information on CR as well as data regarding abundance and size distribution, the population filtration rate was calculated to be 1.6 m³/m² per day in the ark-shell culturing ground of Mae-no-umi (mean water depth, ∼3 m), corresponding to the potential to locally process a volume of water equivalent to the water column within 2 days. Because the culturing ground accounts for 12% of Mae-no-umi (mean water depth, ∼8 m), the ark shell seems to play an important role in its material cycling.     

Observations on the effect of salinity and photon fluence rate on the induction of sporulation and rhizoid formation in the green alga Enteromorpha prolifera (Müller) J. Agardh (Chlorophyta, Ulvales)

ABSTRACT: Although most members of the genus Enteromorpha are important edible green algae, some species are also potentially economically valuable crops. Samples of E. prolifera were obtained from the Yoshino River estuary, Tokushima, Japan and cultured in laboratory conditions at 10°C, a salinity of 20 psu, under white light with 12 h light : 12 h dark cycle and at a photon fluence rate (PFR) of 40 μmol/m² per s for 30 days. In the present study, the effect of salinity and PFR on the induction of reproductive cells and rhizoid formation were investigated. Synchronous formation of swarmers by thalli was induced in excised disks of 1.2 mm diameter after 2–5 days incubation. The optimum salinity for maturation of reproductive cells was between 5.0 and 52.0 psu, and between 13.2 and 45.3 psu for swarmer release, although the lower limit for swarmer release was 5.0 psu. Maturation of reproductive cells and swarmer release required a PFR higher than 16 μmol/m² per s. The minimum PFR for swarmer release was 8 μmol/m² per s. Many rhizoids were formed between 1.6 and 52.0 psu and photon fluence rates between 8 and 320 μmol/m² per s. Rhizoids were formed in a polarized manner.     

The Effect of Five Stocking Densities on Growth and Yield of Red Swamp Crawfish Procambarus clarkii

A 34-day study was conducted to estimate the effect of stocking density on growth, biomass, and yield of harvestable animals in red swamp crawfish, Procambarus clarkii (Girard). Juvenile crawfish were stocked at l, 2, 4, 8, and 16 crawfish per m² into plastic-lined metal pools planted with rice ( Oryza sativa ) with three replicate pools at each density. Crawfish averaged 35 ± 1.5 mm (SE) total length at the time of stocking.
Growth in total length and weight was significantly affected by density ( P < 0.01), ranging from 91.5 mm and 20.7 g for crawfish stocked at 1 per m² to 62.5 mm and 6.3 g for crawfish stocked at 16 per m². The total crawfish biomass ranged from 20.7 g per m² for crawfish stocked at 1 per m² to 88.7 g per m² at 16 per m². The portion of that biomass made up of harvestable sized animals (>75 mm total length) ranged from 100% at 1 per m² to 0.7% at 16 per m². Gross revenues per ha were projected for crawfish yields at each stocking density with and without a graded product.     

Annual net production of the five Sargassaceae species in Yoro,western Wakasa Bay,Sea of Japan

ABSTRACT:   Annual net production of the five Sargassaceae species was investigated in Yoro, western Wakasa Bay, Sea of Japan. The Sargassaceae species were collected at a depth of 2.0–2.5 m and subjected to stratified clipping for 13 months. Annual net production was estimated at 2407 g dry wt/m² for Sargassum patens , 2132 g dry wt/m² for Sargassum macrocarpum , 1458 g dry wt/m² for Sargassum siliquastrum , 1197 g dry wt/m² for Myagropsis myagroides , and 1471 g dry wt/m² for Sargassum piluliferum . The ratio of annual net production to maximum biomass (P/B_max) for these species ranged between 1.3 and 1.7, being higher than in previous studies which used the same method. Winter storms with strong wave exposure and relatively calm condition in Yoro were considered to augment P/B_max. The total losses estimated from the different units of stratified clipping were compared. If larger and less segregated units were applied, the total loss would decrease. It was suggested that a 50 cm stratum would be applicable to the larger species (3 m or longer) and a stratum of 20 cm or less would be applicable to mid-sized or smaller species (less than 3 m).     

Fish community composition of a tropical nonestuarine embayment in Zanzibar,Tanzania

ABSTRACT:   By using a seine net, fish samples were taken from the nonestuarine Chwaka Bay (Zanzibar, Tanzania) from the mangroves, mud/sand flats and seagrass beds. Sampling was done twice per month between November 2001 and October 2002. In total, 150 fish species belonging to 55 families were identified. Diversity ( H' ) ranged from 1.9 in mud/sand flats to 3.4 within the Chwaka seagrass beds. Mean density of fishes was significantly higher in the mangrove creeks than in any other habitat (mean = 238.7 ind./1000 m²). Highest, but non-significantly different mean biomasses were recorded in the mangrove creeks (1.7 kg/1000 m²) and in the Marumbi seagrass beds (1.6 kg/1000 m²). The mangrove channel had the lowest biomass (0.6 kg/1000 m²). A high overlap in species composition (as high as 93.4% similarity) was found for adjoining habitats (i.e. mangrove creeks and mangrove channel), while habitats that were far apart showed low overlap (6.6% similarity for the Marumbi seagrass beds and mangrove creeks). On average, 58.4 and 63.2% in terms of abundance and biomass, respectively, of the fish assemblage of Chwaka Bay were of commercial fishery importance. Thus, Chwaka Bay appears to be an important juvenile habitat for various commercially important fish species.     

Effect of population density on the growth, feed and protein conversion efficiency and biochemical composition of a tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)

Abstract. Six groups of tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)(mean weight. 20·45 ± l·5g), were reared in 0·34m³ fibreglass tanks at different stocking densities (105, 195, 285, 375, 465 and 555 specimens/m³ water) for 84 days. The objective of the study was to determine the effect of various stocking densities on the growth, nutrition, biochemical composition and survival of M. nemurus. The lowest growth rate appeared in fish at the highest density and the highest was observed in fish stocked in moderate density of 285 and 375 fish/m³ water. Fish production was also lower at relatively low stocking densities of 105 and 195 fish/m³. Food conversion ratio (FCR), protein efficiency ratio (PER) and biochemical composition of M. nemurus indicate that there exists an optimum stocking density which lies between 285 and 375 fish/m³.     

Food Production and Water Conservation in a Recirculating Aquaponic System in Saudi Arabia at Different Ratios of Fish Feed to Plants

An indoor aquaponic system (i.e., the integration of fish culture with hydroponic plant production in a recirculating setup) was operated for maximizing water reuse and year-round intensive food production (Nile tilapia, Oreochromis niloticus , and leaf lettuce) at different fish feed to plants ratios. The system consisted of a fish culture component, solid removal component, and hydroponic component comprising six long channels with floating styrofoam rafts for holding plants. Fish culture effluents flowed by gravity from the fish culture component to the solid removal component and then to the hydroponic component. Effluents were collected in a sump from which a 1-horsepower in-line pump recirculated the water back to the fish culture tanks at a rate of about 250 L/min. The hydroponic component performed as biofilter and effectively managed the water quality. Fish production was staggered to harvest one of the four fish tanks at regular intervals when fish attained a minimum weight of 250 g. Out of the total eight harvests in 13 mo, net fish production per harvest averaged 33.5 kg/m³ of water with an overall water consumption of 320 L/kg of fish produced along with the production of leaf lettuce at 42 heads/m² of hydroponic surface area. Only 1.4% of the total system water was added daily to compensate the evaporation and transpiration losses. A ratio of 56 g fish feed/m² of hydroponic surface effectively controlled nutrient buildup in the effluents. However, plant density could be decreased from 42 to 25–30 plants/m² to produce a better quality lettuce.     

Bioremediation of organically enriched sediment deposited below fish farms with artificially mass-cultured colonies of a deposit-feeding polychaete <Emphasis Type="Italic">Capitella</Emphasis> sp. I

ABSTRACT:   For bioremediation of organically enriched sediment deposited below fish farms, the extremely high potential for population growth of a deposit-feeding polychaete, Capitella sp. I, in the organically enriched sediment, and the effect on decomposition of organic matter in the sediment, were examined. A mass-culturing technique was conducted for this species. Bioremediation experiments were conducted on the organically enriched sediment in a fish farm in Kusuura Bay, Japan in 2003–2006. Approximately 1.7 million individuals of the worms were placed on the sediment below one net pen in December 2003, 9.3 million individuals in November 2004, and 2.2 million individuals in November 2005. After the worms were spread on the sediment, they rapidly increased in number and reached the highest densities of approximately 134 000 inds/m² in February 2004, 527 000 inds/m² in March 2005 and 103 000 inds/m² in January 2006. In the process of rapid population growth, the decomposition of the organic matter of the sediment was enhanced markedly. Our results demonstrate that the promotion of population growth by spreading cultured colonies of Capitella can enhance the decomposition rate of organic matter markedly in organically enriched sediment below fish farms. This method is promising for minimization of the negative effects of fish farms.     

Preliminary study on the production of the tilapia, Oreochromis spilurus (Günther), cultured in seawater cages

Abstract. A preliminary study was conducted to assess the performance of the tilapia, Oreochromis spilurus (Günther), cultured in seawater cages at different stocking densities during the nursing and rearing phases. The stocking densities tested were 200, 400 and 600 fish/m³ during the nursing phase and 100, 200, and 300 fish/m³ during the rearing phase.
In both growth phases, no significant differences (P>0.05) were observed among the different stocking densities on the mean individual final weight, daily growth rate, feed conversion ratio and survival rate. Yields in cages stocked with 400 and 600 fish/m³ during the nursing phase, however, were significantly (P<0.05) higher compared with cages stocked with 200 fish/m³. No significant differences (P>0.05) were observed between 400 and 600 fish/m³. A density of 600/m³ is therefore considered to be optimum for the nursing phase.
Yields of cages during the rearing phase increased significantly (P<0.01) with the increase in stocking density. After grading the fish, however, no significant differences (P>0.05) were observed when only fish bigger than 150g were considered. The occurrence of exophthalmia (cataract) was observed in two of the four replicates at the highest stocking density (300 fish/m³) during the rearing stage. Therefore, a stocking density of 200 fish/m³ is considered optimum for the rearing phase.     

Survival and movement of hatchery-reared red snapper on artificial habitats in the northern Gulf of Mexico

Abstract  Hatchery-reared age-0 red snapper, Lutjanus campechanus (Poey), were released onto artificial habitats in the Gulf of Mexico. Fish showed 12.7% survival after 7 months on small habitats (0.86 m³) and 3.1% survival after 8 months on large habitats (3.9 m³). Emigration was estimated by the movement of fish to unstocked habitats and accounted for 76.8% of the total decline in abundance at release sites after 26 days. Fish showed higher survival and growth rates on small habitats (27.6% at 26 days; 0.33 mm day⁻¹) compared with large habitats (13.2% at 34 days; 0.26 mm day⁻¹), which may have been due to increased predation and competition on large habitats. Fish became evenly distributed among adjacent habitats 26 days after release, indicating that stocking densities at release habitats were above carrying capacities. These observations suggested that providing additional habitat around red snapper release sites would increase survival.     

Population ecology of cave armoured catfish, Ancistrus cryptophthalmus Reis 1987, from central Brazil (Siluriformes: Loricariidae)

Abstract –  The population ecology of Ancistrus cryptophthalmus (Reis 1987) was studied by mark–recapture technique in caves from the São Domingos karst area, State of Goiás, northeastern Brazil. Total population sizes estimated for Angélica and Passa Três Caves were 20,000 and 1000 individuals, respectively. Densities around 1.0 individuals per m² in Angélica, Bezerra and São Vicente I Streams, and 0.6 individuals per m² in the smaller Passa Três Stream may be considered high for cavefish standards, as well as for epigean loricariids. As expected for benthic grazers, cave catfish are highly sedentary. The distribution of size classes did not differ among caves and within the same cave throughout the studied dry seasons; on the contrary, the condition factor decreased throughout this period probably because of the progressive depletion of organic matter available as food. Low proportions of mature individuals, low growth rates (average = 0.5 mm month⁻¹) with cases of negative growth and high longevities (8–10 years) point to a precocial lifestyle, typical of troglobitic species.     

Biomass and production of the euphausiid Euphausia pacifica along the coastal waters off north-eastern Japan

ABSTRACT:   Biomass and production of Euphausia pacifica off south-eastern Hokkaido (41–43°N), Sanriku (38–41°N), and Joban (36–38°N) were investigated every two months from March 1997 to February 1998. High biomass was found in summer–autumn off south-eastern Hokkaido, and in the late winter–early summer off Sanriku and Joban. Annual mean biomass was 381, 314 and 258 mg C/m² off south-eastern Hokkaido, Sanriku, and Joban, respectively. The total production (sum of flesh, moults and eggs) during the survey period off south-eastern Hokkaido (3829 mg C/m²) was comparable with that off Sanriku (3872 mg C/m²); both were much higher than that off Joban (2243 mg C/m²). Somatic production during the survey period contributed the highest proportion (51.5–70.9%) to the total production in each coastal area. The somatic production–biomass ratio in each coastal area (5.2–6.9) was an intermediate value among 25 populations of 16 euphausiid species previously reported. This effect resulted from the negative factor of stagnated growth of adults during summer–winter, coupled with positive factors including continuous occurrence of larvae which show high growth rate throughout the year off Sanriku and Joban, and the numerous larvae occurring in October off south-eastern Hokkaido.     

Migration of anadromous white-spotted charr <Emphasis Type="Italic">Salvelinus leucomaenis</Emphasis>, as determined by otolith strontium: calcium ratios

ABSTRACT:   The migratory history of anadromous white-spotted charr Salvelinus leucomaenis collected from Japanese coastal waters, was examined in terms of strontium (Sr) and calcium (Ca) uptake in the otolith, by means of wavelength dispersive X-ray spectrometry using an electron microprobe. Otolith Sr concentration or Sr : Ca ratios of anadromous S. leucomaenis , fluctuated strongly along the life history transect in accordance with the migration (habitat) pattern from sea to fresh water. The anadrmous S. leucomaenis showed phase L (low Sr : Ca ratio) from the core to the point 1000–2500 µm distant, averaging 1.3 × 10⁻³ to 2.7 × 10⁻³ and thereafter, the ratios increased sharply, being higher than 5.0 × 10⁻³ to 10.0 × 10⁻³. These findings indicated that otolith Sr : Ca ratios reflected individual life histories, enabling a sea habitat to be identified from a freshwater habitat in this species.     

The influence of different levels of dietary vitamin E on sea bass Dicentrarchus labrax flesh quality

Sea bass Dicentrarchus labrax fillet quality was investigated after feeding with four diets (A, B, C or D) containing different levels of dietary vitamin E (139 mg kg^–1, 254 mg kg^–1, 493 mg kg^–1 and 942 mg kg^–1, respectively). Six-hundred and eighty fish (mean initial weight 208 g) were equally divided into four 20 m³ tanks and fed for 87 days. Filtered seawater with a temperature ranging from 18.2 to 26.3 °C was supplied continuously. At the end of the experiment, fish were stored at 1 °C for 12 days. At one, three, six, nine and 12 days, 20 fish per group were processed for proximate composition, vitamin E and induced thiobarbituric acid reactive substances (TBARs) analyses. No significant differences in proximate composition were registered between groups. The flesh lipid content ranged from 88.0 g kg^–1 (group B) to 96.8 g kg^–1 (group A). Vitamin E fillet content was significantly different between groups, reaching levels of 98.0, 150.7, 225.2 and 302.0 μg g^–1 lipids for group A, B, C and D, respectively. Induced TBARs values were statistically different only for group A compared with the other groups. No significant variations were registered in relation to preservation time. Because of the positive influence of vitamin E on seafood quality and the correlation between its dietary level and flesh deposition, the α-tocopherol content of the diet should be well above fish minimum requirements.     

Nutrient requirement for zoospore formation in two alariaceous plants Undaria pinnatifida (Harvey) Suringar and Alaria crassifolia Kjellman (Phaeophyceae: Laminariales)

ABSTRACT:   Sporophyll formation in two alariaceous plants, Undaria pinnatifida and Alaria crassifolia , was studied in relation to the nutrient requirements. The sporophylls of U. pinnatifida formed zoosporangia when they had N and P contents greater than 1.4 kgN/m³ and 0.74 kgP/m³. This indicates that these values are the critical nutrient levels for zoospore formation in U. pinnatifida . In the sporophytes of A. crassifolia , many sporophylls with zoosporangia showed nutrient contents higher than 6.25 kgN/m³ and 1.70 kgP/m³. These results suggest that the U. pinnatifida can form zoospores at lower levels of N and P contents than A. crassifolia . Both species often formed zoosporangial sori on the blades in the late period of each reproductive season. The fertile parts of the blade showed N and P contents higher than the critical levels. This phenomenon indicates that the blades have the capability to form zoosporangial sori if there is a sufficient accumulation of nutrients for zoospore formation. The zoospore formation on the blade seems to be accomplished by an overflow of excess nutrients from sporophylls into the blade, or by accumulating sufficient nutrients to form sori even if the sporophylls are not formed.     

Creation of artificial upwelling areas for brown trout, Salmo trutta, spawning in still water bodies

Abstract  Brown trout, Salmo trutta L., spawning sites were constructed by creating areas of artificial upwelling water, 252 ± 37 mL m⁻² min⁻¹ (95% CL), through appropriately sized spawning gravel substrate in 3 m² vessels buried in the bottom of a 150-m² pond. Natural spawning occurred in the vessels during autumn 2001–2004, with hatching and alevin swim up the following spring. In areas of upwelling, egg survival was 85–95%, while no live eggs were observed in areas without upwelling. In areas with upwelling, the maximum density of live eggs at the eyed stage was 570–1510 eggs m⁻². In spring 2004 and 2005, the density of alevins was estimated at 322 (±187) m⁻² and 567 (±217) m⁻², respectively, in areas with upwelling water, compared with 35.2 ± 25.4 m⁻² in areas without upwelling water in 2004.