Effects of light intensity on molting,growth, precocity,digestive enzyme activity,and chemical composition of juvenile Chinese mitten crab <Emphasis Type="Italic">Eriocheir sinensis</Emphasis>

A 74-day growth trial was carried out to investigate the effects of light intensity on the juvenile Chinese mitten crab, Eriocheir sinensis, under semi-natural conditions. The experiment had three light intensity treatment groups, natural light (NL), middle light (ML), and low light (LL), as light intensity became weaker. The results indicated that light intensity had no significant effect on molting interval and molting frequency but did have a significant effect on the molting weight gain of the crab. Molting weight gain in group NL was significantly higher than that in group LL (P < 0.05). Specific growth rate in weight (SGRw) and in carapace width (SGRcw), weight gain, and final body weight were significantly affected by light intensity (P < 0.05). No significant difference was detected in survival between groups (P > 0.05). The precocious rate in groups NL, ML, and LL was 26.14, 15.48, and 17.14%, respectively. The precocious rate in group NL was significantly higher than that in groups ML and LL (P < 0.05). Chemical composition of the crab body was significantly affected by light intensity, but the activity of alkaline phosphatase, trypsin, and pancreatic lipase was not significantly affected by light intensity. The results indicated that the submitted light intensity was useful in reducing the precocious rate without affecting the normal growth of juvenile E. sinensis.     

Recruitment of catarina scallop (Argopecten ventricosus) larvae on artificial collectors off the NE coast of the Gulf of California

We evaluated recruitment of larvae of catarina scallop, Argopecten ventricosus, in the area of Puerto Peñasco, NE Gulf of California. We moored artificial collectors in six sites from June 2007 to August 2008 and replaced them every 2 months. We used monthly (July 2002–September 2011) sea surface temperature (SST, °C) and surface chlorophyll‐a concentration (SSChl, mg m^?3) Aqua/MODIS satellite data to describe seasonal environmental behaviour study area. Also, we recorded bottom temperature at each site every 4 h, and every 2 months measured sea surface salinity, temperature and dissolved oxygen. We used a repeated measures anova to evaluate differences in the number of recruited spat between main factors, and analysed the presence of multimodal spat shell size frequency distributions. Overall, spat recruitment was negatively correlated with seawater temperature and showed higher spat recruitment abundances throughout winter, which is the season with the highest surface chlorophyll a concentration. We estimated multimodal shell size frequency distributions characterized by more than one modal size. The natural collection of A. ventricosus spat on artificial collectors in the area can be successfully performed over a protracted period (November–December to May–June). Our results extend the area where collection of A. ventricosus spat can be successful.     

Biochemical characterization of Siberian sturgeon Acipenser baeri and sterlet Acipenser ruthenus milt plasma and spermatozoa

This paper provides data concerning biochemical composition of milt of two sturgeon species, Siberian sturgeon bred in aquaculture facility of Inland Fisheries Institute in North Poland and sterlet (from two different populations from Danube and Odra). Milt plasma of Siberian sturgeon and sterlet, when compared to teleost fish, is characterized by much lower osmolality (up 70 to 96 mOsm kg⁻¹) and protein concentration (0.24–0.58 g l⁻¹). In spite of the presence of an acrosome and acrosin the antiproteinase activity of seminal plasma was low (12.79–25.40 U l⁻¹). Activities of arylsulfatase and β-N-acetylglucosaminidase were found in spermatozoa. This agrees with the presence of an acrosome in sturgeons sperm. Similarly to mammals, these enzymes are also present in milt plasma. We determined a range of enzymatic activities from the minimal (seminal plasma) to the maximal damage (supernatants obtained after freezing-thawing without cryoprotectant). Activities of arylsulfatase, β-N-acetylglucosaminidase, lactic dehydrogenase and acid phosphatase were released from spermatozoa after freezing-thawing. For this reason they are good potential candidates as a markers of cryoinjury to sperm acrosome and midpiece. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ontogenetic development of digestive enzymes and effect of starvation in miiuy croaker <Emphasis Type="Italic">Miichthys miiuy</Emphasis> larvae

The ontogenetic development of the digestive enzymes amylase, lipase, trypsin, and alkaline phosphatase and the effect of starvation in miiuy croaker Miichthys miiuy larvae were studied. The activities of these enzymes were detected prior to exogenous feeding, but their developmental patterns differed remarkably. Trypsin activity continuously increased from 2 days after hatching (dah), peaked on 20 dah, and decreased to 25 dah at weaning. Alkaline phosphatase activity oscillated at low levels within a small range after the first feeding on 3 dah. In contrast, amylase and lipase activities followed the general developmental pattern that has been characterized in fish larvae, with a succession of increases or decreases. Amylase, lipase, and trypsin activities generally started to increase or decrease at transitions from endogenous to exogenous feeding or diet changes, suggesting that these enzymatic activities can be modulated by feeding modes. The activities of all the enzymes remained stable from 25 dah onwards, coinciding with the formation of gastric glands and pyloric caecum. These results imply that specific activities of these enzymes underwent changes due to morphological and physiological modifications or diet shift during larval development but that they became stable after the development of the digestive organs and associated glands was fully completed and the organs/glands functioned. Trypsin and alkaline phosphatase were more sensitive to starvation than amylase and lipase because delayed feeding up to 2 days after mouth opening was able to adversely affect their activities. Enzyme activities did not significantly differ among feeding groups during endogenous feeding; however, all activities were remarkably reduced when delayed feeding was within 3 days after mouth opening. Initiation of larvae feeding should occur within 2 days after mouth opening so that good growth and survival can be obtained in the culture.     

Biochemical,Physical, Chemical,and Microbiological Assessment of Blue Shrimp (Litopenaeus stylirostris) Stored in Ice

Postmortem changes in blue shrimp (Litopenaeus stylirostris) muscle were studied on the basis of biochemical, chemical, physical, and microbiological changes during an 18 day storage period at 0°C. Adenosine 5′-triphosphate (ATP) content, breakdown products, K-value, pH, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), water holding capacity (WHC), color, and texture (shear force) changes were examined. Also, total mesophilic and psychrophilic bacterial counts were measured. K-value increased linearly (r² = 0.98) from an initial value of 1.37 ± 0.59 to 59.42 ± 6.05% at Day 18. Spoilage indicators TVB-N and TMA-N increased from 29.56 ± 1.33 and 0.69 ± 0.25 to 39.04 and 2.04 ± 0.59 mg of N/100 g at Day 18, respectively; meanwhile, the total viable counts of mesophilic and psychrophilic bacteria increased from 3.48 ± 0.44 and 2.61 ± 0.29 log CFU/g to 6.27 ± 0.21 and 7.14 ± 0.39 log CFU/g, respectively, which indicated spoilage at the end of the storage period. The pH, texture, WHC, and color were affected (p < 0.05) during the storage period. Overall, results indicate that blue shrimp muscle quality was maintained for 12 days of storage in ice.     

Compensatory growth and body composition of juvenile black rockfish <Emphasis Type="Italic">Sebastes schlegeli</Emphasis> following feed deprivation

ABSTRACT:   Compensatory growth, feeding rate, feed efficiency and chemical composition of juvenile black rockfish (mean weight 1.43 g) were investigated for 35 days after a 14-day feed deprivation treatment under four feeding conditions: one group continuously fed (control) and the other three groups fasted for 5 days (F5), 10 days (F10) and 14 days (F14). All fasted fish were re-fed from day 15. Only F5 achieved the same body weight as the control, indicating that complete compensation occurred in F5. The specific growth rate (SGR) of F5 was the highest at day 21 and then decreased thereafter, showing higher values than the control at days 21, 28 and 42. In contrast, although SGRs of F10 and F14 were higher than that of the control during the whole refeeding period except day 21, they did not catch up the control in body mass, indicating that only partial compensation occurred in F10 and F14. The feeding rate (FR) of all groups except F14 changed in a pattern similar to SGR (Spearman's rank correlation, r _s > 0.9), suggesting that SGR varied depending on FR. Similar feeding efficiencies (FEs) were found in the four groups and they did not vary significantly during the whole refeeding period, suggesting that FE was not the factor affecting SGR. At day 14, the ratios of lipid to lean body mass in F10 and F14 were lower than those in the control and F5, and there was no difference between the control and F5. At day 49, however, only F14 showed a lower value than the other three groups, and there was no difference among the three groups. These results indicate that juvenile black rockfish fasted for 5–14 days can exhibit compensatory growth after refeeding, but timing and degree vary depending on the duration of feed deprivation.     

How much variation can be explained by seasonal,spatial and environmental effects in nekton assemblages of the Terminos Lagoon?

• 1. The coastline is very sensitive to both climatic and human influences but also provides essential goods and services upon which human welfare depends. Species inhabiting these coastal areas provide valuable resources and enhance ecosystem functioning: it is therefore essential to understand the main factors influencing species abundance patterns. The aim of this study is to estimate the amount of variation in nekton coastal assemblages explained by spatial, temporal and environmental variables.
• 2. Nekton sampling was carried out over 17 months in the Terminos Lagoon, a reserve area situated in the Gulf of Mexico, using a shrimp trawl. At each station, 11 environmental variables were recorded. The influence of seasonal, spatial and environmental variables on nekton species abundance was analysed using Partial Canonical Correspondence Analysis (PCCA).
• 3. The explanatory variables explained only 19.7% of the total observed variation in the nekton community for the Terminos Lagoon. The major part of the explained variation was due to the spatial effect (9.2%), while environmental variables and seasonality explained only 3.6% and 0.8%, respectively, suggesting the necessity to consider experimental fishing design in such artisanal fisheries.
• 4. Results also suggest focusing on more integrative indicators of community structure such as measures of taxonomic diversity based on presence/absence or on measures related to functional attributes of communities rather than using species abundance patterns to predict changes in coastal ecosystems.

Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of formalin on total haemocytes count and histopathological changes in the shrimp Litopenaeus schmitti (Pérez‐Farfante & Kensley 1997)

Formalin is used in shrimp industry to eliminate ectoparasites and as a disinfectant. However, the effect of formalin on shrimp's defense mechanism is unknown. Several biomarkers were used to assess the immune response of juveniles of the shrimp Litopenaeus schmitti exposed to different concentrations of formalin (10, 25 and 50 mg L^?1) during 24 and 48 h. Formalin concentrations of 25 and 50 mg L^?1 produced a significant reduction in the total haemocyte count at both 24 and 48 h. Peroxidase and phenoloxidase activity did not show variations. The total protein concentration in haemolymph of shrimps was not significantly different between experimental groups. Histological analysis showed hyperplasia in the gills of animals exposed at 10 mg L^?1 for 24 h; however, the exposure at 25 and 50 mg L^?1 caused necrosis in gills, hepathopancreas and the antennal gland.