Functional linseed fibres and their impacts on silver catfish (Rhamdia quelen) nutrition

This study was conducted with the objective of evaluating the combination of different ratios of soluble and insoluble linseed fibre for silver catfish (Rhamdia quelen). For this, the soluble and insoluble fractions were concentrated separately and combined in four ratios (1:0.5, 1:1, 1:2, 1:4), which were added to silver catfish diets and evaluated in a bioassay. After 45 days of receiving the experimental diets, the animals were submitted to biometry to collect data and tissues. The experimental design was completely randomized, with five treatments and four replications and the means were compared by Tukey's test (p < .05). Diets 1:2 and 1:4 provided higher weight gain, specific growth rate and crude protein deposition to the fish, whereas only the 1:4 diet reflected higher crude body protein. The 1:0.5 diet altered the trypsin activity in the intestine, and, together with the 1:4 diet, it provided a higher intestinal villi height. Body yield, somatic and digestive parameters, chymotrypsin activity and glucose, glycogen and liver protein were not altered, regardless of the experimental diets. In conclusion, the results indicate that linseed fibre acts effectively as a growth promoter in silver catfish diets, with the use of 1:2 and 1:4 ratios optimizing its prebiotic action.     

Effect of different diets on larval production, quality and fatty acid profile of the marine ornamental shrimp Lysmata amboinensis (de Man, 1888), using wild larvae as a standard

The present work evaluates the influence of broodstock diets [Marine Cuisine^®– MC, MC supplemented with highly unsaturated fatty acid- (HUFA) enriched Artemia biomass – MC + AB, and MC supplemented with squid – MC + S] on larval production, newly hatched and early zoeal stage survival and fatty acid profile of newly hatched larvae of Lysmata amboinensis . These parameters are compared with those from larvae hatched from embryos spawned in the wild. The number (±SE) of larvae produced with MC and MC + S (1077 ± 219 and 1103 ± 184, respectively) was similar to that in broodstock carrying embryos spawned in the wild (1224 ± 111), while those fed MC + AB displayed significantly lower values (1044 ± 161). Larvae produced with MC + AB displayed lower survival for all starvation periods, while larvae spawned in the wild displayed the highest survival. No larvae resisted 144 h of starvation and none moulted to zoea II. The fatty acid comparison revealed that larvae from embryos spawned in the wild displayed the highest levels of DHA, as well as higher DHA/EPA and n -3/ n -6 ratios. These results suggest that broodstock diets commonly used to promote ornamental shrimp's maturation (based on mixed frozen components) are far from being optimal.     

Natural food evaluation and water quality in zero water exchange culture of Litopenaeus vannamei fertilized with wheat bran

The aim of this study was to analyze the influence of organic fertilizer on the availability of natural food (plankton and benthos) and water quality. Two fertilization protocols were adopted using inorganic and organic fertilizers with shrimp (stocked treatment) and their controls (unstocked treatment). Experimental units consisted of 12 circular fiberglass tanks (500 l) with estuarine sediment, individual aeration and no water exchange. In stocked treatments were used 40 juveniles/m², and they were fed with 35% crude protein marine shrimp ration, three times a day. Under the organic fertilization protocol, the plankton showed higher abundance of Nitzschia and rotifers, the phytobenthos consisted mainly of Nitzschia, Amphiprora and Oscillatoria, the epibenthos was represented mainly by nematodes and rotifers, and the macro-invertebrates were mainly oligochaetes. In relation to inorganic fertilization, the plankton was represented mainly by Coscinodiscus and rotifers, the phytobenthos consisted mainly of Amphiprora and Oscillatoria, the epibenthos was represented mainly by nematodes and rotifers, and the macro-invertebrates were mainly oligochaetes. Dissolved oxygen was higher for organic fertilizer (6.16 ± 0.98 mg/l) than for inorganic (5.92 ± 1.19 mg/l) while the other water quality parameters did not present significant differences. Survival was similar in the two fertilization regimes (96.6%). Final body weight was 11.89 ± 1.73 g for the inorganic fertilizers and 12.28 ± 1.71 g for organic fertilizer. It is concluded that wheat bran showed good performance in the water quality without exchange, in the availability of natural food, and in the growth and survival of the shrimps in the microcosms.     

Gonadal structure analysis of Macrobrachium amazonicum (Heller, 1862) from a wild population: a new insight into the morphotype characterization

The aim of this work is to correlate the histological gonad analysis of adult male Macrobrachium amazonicum of a wild population with morphotypes identified in populations reared in earthen ponds. A total of 500 adult male specimens were collected in the Mosqueiro Island, Municipality of Belém, State of Pará, Brazil. The animals were classified on the basis of body and cheliped colour, second right cheliped spination, total length, cheliped length and weight. The gonads of each morphotype were fixed, processed by histological techniques and stained with haematoxylin and eosin. All four morphotypes, translucent claw (TC), cinnamon claw (CC), green claw 1 (GC1) and green claw 2 (GC2), were identified in the wild population, indicating the same population structure described for cultured animals. The M. amazonicum testes are composed of multiple lobes. The TC gonads showed a population of germ cells in the eccentric portion of the seminiferous tubule and few spermatozoa in the central region. Cinnamon claw males exhibited a large cell population with intense meiotic activity and sparse spermatozoa. Regardless of the different external morphologies of GC1 and GC2, no histological differences were found in their gonads; both had a large number of gametes and similar spermatogenic cell population. Despite the external morphological evidences of the four morphotypes, the histological criteria indicate the existence of only three morphotypes: TC, CC and green claw (GC).     

Influence of the type of collector and collector preparation periods on the settling rate of the scallop Nodipecten nodosus L. in the laboratory

We analysed the settling rate of Nodipecten nodosus L. scallop spats during winter and spring, testing different types of collectors and collector preparation periods. Larval rearing was conducted with water exchange every 48 h, density at 2 larvae mL⁻¹ and feeding between 0.5 and 2 × 10⁴ microalgae cellsmL⁻¹. The recovery larvae based on D-larvae produced were 31.6% (Winter Trial) and 47.2% (Spring Trial), without any antibacterial additives. The mean settling rates obtained in Winter Trial were from 0.04% to 0.79% withstand in Spring Trial were 24.99–48.65%. In the Winter Trial, there was no statistical difference between the settling rate of collectors prepared for 6 or 12 days. The settling rates of the netlon collectors with pine leaves were up to 19 times higher than those of the other types of collectors. In the Spring Trial, there was no statistical difference between the settling rates of the netlon and plastic net fruit collectors. Collectors with pine leaves produced a yield of spats up to 48.65%, more than those without pine leaves ( P <0.01). The efficiency of larval rearing and settling obtained in spring, pine leaves and low-cost local material indicate the feasibility to improve and facilitate regular production of N. nodosus spats for promotion of the growth of scallop culture in Brazil.     

Effects of alternate phases of fish oil and vegetable oil-based diets in Murray cod

Fish oil (FO)- and canola oil (CO)-based diets were regularly alternated in a daily cycle (amCO: alternation of CO in the morning and FO in the afternoon, and pmCO: alternation of FO in the morning and CO in the afternoon) or in a series of weekly cycles (2W: alternation of 2 weeks on CO and 2 weeks on FO, 4W: alternation of 4 weeks on CO and 4 weeks on FO), over a 16-week period in juvenile Murray cod ( Maccullochella peelii peelii ). No significant differences were observed between any of the treatments in relation to the final weight. However, fish subjected to the 2W schedule were larger ( P >0.05) than all other treatments (37.2 ± 0.30 vs. 34.3 ± 0.58 in the control treatment). Fish receiving the 2W treatment had a significantly lower total net disappearance of eicosapentaenoic acid 20:5n-3 (EPA) and docosahexaenoic acid 22:6n-3 (62.1% and 24.0% respectively) compared with the control treatment (fish continuously fed a blend of 50% FO and 50% CO). Likewise, Murray cod receiving the amCO daily schedule had a significantly lower total net disappearance of EPA in comparison with the CD and pmCO treatments. These data point towards the existence of cyclical mechanisms relative to fatty acid utilization/retention.     

Geographic variability of sardine growth across the northeastern Atlantic and the Mediterranean Sea

This study describes broad-scale spatial variations in sardine growth across the northeastern Atlantic and Mediterranean waters using opportunistic samples collected in recent years. More detailed information on spatial, decadal and seasonal growth variations is provided for the Iberian-Biscay region using data collected in acoustic surveys since the mid-1980s. Growth curves are fitted to annual or monthly length-at-age data using a robust Von Bertalanffy model; parameters for recent samples are compared with literature information using an auximetric plot while differences between areas within the Iberian-Biscay region are tested by log-likelihood ratio tests. Sardine growth performance is generally lower in the Mediterranean and declines across the northeastern Atlantic from the English Channel to north Morocco but increases sharply off Mauritania. Lower growth of Mediterranean sardines is possibly associated to the overall oligotrophy of this Sea while differentiation from the Atlantic is likely sustained by reproductive isolation between populations from the two areas. Within the northeastern Atlantic, size- and age related migrations may partly explain differences in maximum length/age and mean length-at-age between neighbouring areas but the broad-scale latitudinal decline in growth is consistent with adaptation to the north–south decline in seasonal temperature gradients and to the annual cycles of plankton production. Within the Atlantic Iberian waters, sardine grows and improves in condition during spring and summer when the allocation of energetic resources for gonad development cease, temperature is close to the annual maxima and plankton production is high. Variation in sardine length-at-age and growth within the Atlanto-Iberian stock area has implications for stock structure and needs to be taken into account in the calculation of weight and maturity-at-age for assessment purposes. No evidence of broad temporal changes in sardine growth within the Iberian-Biscay region is obtained.     

Bio-economical and ethical impacts of alien finfish culture in European inland waters

Since 1989, and in comparison to the global trend, inland aquaculture production of European finfish has declined. To date, the yearly European freshwater aquaculture production is 371,727 tons, valued at over US$1 billion. Indigenous species accounted for less than one-third of the production, whereas alien species (a species that has been moved beyond its natural range of distribution) accounts for the remainder. However, in general, indigenous species command a higher market price. Currently, food quality and food safety are leading concerns of consumers, and European consumers are also becoming alert to environmentally detrimental practices. Therefore, to aim at economic sustainability, the sector needs to satisfy consumer expectations of environmentally friendly practices. It is believed that farming alien finfish species can threaten local biodiversity through escapes, and this represents a current environmental concern relative to aquaculture. In this context, an attempt is made in this paper to understand and quantify the impacts of alien finfish cultivation in European inland waters, and to suggest remedial measures.     

Seasonal variation in the condition index of Pacific oyster postlarvae (Crassostrea gigas) in a land‐based nursery in Sonora,Mexico

This study examined the seasonal variation in the condition index (CI) of Crassostrea gigas postlarvae (<5 mm) that were cultivated at a commercial hatchery. Oysters were sampled weekly at the nursery using seawater from a lagoon for the grow‐out that precedes commercialization. Temperature, salinity, seston, chlorophyll a, oxygen and pH were recorded at each sampling and water samples were taken to identify phytoplankton groups and their abundance. High levels of primary productivity, chlorophyll a and seston were detected during summer, but the highest CI occurred in winter. During winter, elevated phytoplankton biomass was composed by diatoms and phytoflagellates, which served as the main food source and promoted weight gain in this season. Variations in salinity, oxygen and pH were not related to differences in the CI. However, it appears that the wide temperature variation affected functions, such as feeding activity, apparently enhancing ingestion during winter (mean 16.5±1.4 °C) and reducing ingestion during summer (mean 31±1.5 °C). Winter production resulted in postlarvae with a homogeneous size range and a high CI, indicating that winter is more favourable to start cultivation. The CI represents a practical means to determine the physiological state of postlarvae before transfer to cultivation sites.     

水稻籼粳杂种不育性的多基因遗传不平衡

本文研究和讨论了水稻亚种间远缘杂种不育性的起源。就杂种不育性的遗传本质,作者提出了多基因遗传不平衡假说:远缘杂种不育性的遗传属于孢子体——配子体的互作,且存在一个多基因系统支配下的一种特殊的配子体选择方式对不育性起作用。具有r个遗传分歧的基因位点(无论连锁或独立)的远缘品种杂交F_1产生的配子中分为平衡配子和不平衡配子。平衡配子的r个基因位点为亲本基因组合类型,拥有亲本之一的整套基因系统而能正常发育;而不平衡配子含有双亲的部分基因系统,由于遗传分歧双亲的基因系统在单倍性细胞中不能很好地配合协调或互补,发育过程的障碍就可能产生败育。在平衡配子和极不平衡配子之间存在各种中间类型,配子体选择按S~(r+u)进行。我们的试验结果结合过去的研究,说明水稻亚种的分化是自然选择作用于遗传变异的结果,生殖隔离是籼亚种和粳亚种连续积累的遗传分歧的产物。