Satiation meal and the effects of meal and body sizes on gastric evacuation rate in brook trout Salvelinus fontinalis fed commercial pellets

Gastric evacuation (GE) experiments were performed on brook trout Salvelinus fontinalis fed commercial food pellets. The experiments included small fish (36 g; 15 cm total length, L_T) fed meals of 0·2, 0·4 and 0·8 g and large fish (152 g; 23 cm) fed meals of 0·8, 2·0 and 4·0 g at temperatures ranging from 15·1 to 18·2° C. The stomach contents were thereafter sampled and weighed at 3 h intervals until the first empty stomach was observed. The course of GE was examined by use of a general power function of the data that revealed that the square‐root function described the GE rate (GER) by the current stomach content mass independently of original meal size. Using the square‐root function, the relationship between GER and fish size was described by a power function of fish length, whereas the effect of temperature was described by a simple exponential function. GER of the commercial pellets fed to S. fontinalis could thus be described by (g h^?1), where S_t is stomach mass (g) at time t (h), L is total fish length (cm) and T is temperature (° C). The result of this study should provide a useful tool for planning of feeding regimes in production of S. fontinalis by optimizing growth and minimizing food waste.     

Anaesthesia and transport of juvenile tambaqui Colossoma macropomum (Cuvier, 1818) with tricaine methane‐sulphonate: Implications on secondary and oxidative stress responses

The aim of this study was to evaluate the anaesthetic efficacy and the effect of sedation with tricaine (TMS^®), also known as MS‐222, on secondary and oxidative stress parameters in juvenile tambaqui, Colossoma macropomum transported in hyperoxia for 2, 6 and 10 hr. Juveniles were placed in aquaria containing six different concentrations of buffered tricaine (150, 180, 210, 240, 270 and 300 mg/L) and the times for anaesthesia induction and recovery determined. Fish transported in hyperoxic conditions were investigated for glycemia, ionic concentration (K⁺, Ca⁺⁺, Na⁺) and osmolality, haematocrit (Ht) and haemoglobin concentration (Hb), partial pressure of gases (pCO₂ and pO₂), pH and bicarbonate concentration () in whole blood collected from caudal vasculature. Total antioxidant capacity against peroxyl radicals (ACAP), glutathione‐S‐transferase (GST) activity and lipid peroxidation levels (TBARS) were investigated in gills, brain and liver. All concentrations of TMS^® induced deep anaesthesia in juvenile tambaqui in this study. A concentration of 240 mg/L of TMS^® was sufficient to induce rapid anaesthesia (<3 min) with uneventful recovery (<5 min). In light of the secondary and oxidative stress responses of fish transported using TMS^®, which were generally not significantly different compared to responses of fish transported in anaesthetic‐free water, sedation with 20 mg/L is not advantageous and therefore is dispensable for the transport of this species for up to 10 hr.     

Gastric digestion and evacuation in whiting, Merlangius merlangus (L.)

Three meal sizes of sandeels were fed to whiting in order to monitor the evacuation of food out of the stomach. The stomach contents were sampled at intervals after feeding, using a stomach pump. In such experiments, the proportion of fish with empty stomachs tends to increase with time and, since stomach contents are limited to zero or positive values, the variance of the stomach contents becomes censored at zero. This tends to produce a curved relationship between mean stomach content and time, which gives the impression that evacuation rate slows down at low levels of stomach fullness. By taking account of censoring, it was shown that the evacuation curve generated for whiting was consistent with and could be generated from a linear model in which the rate of gastric evacuation exhibited by the fish was constant and independent of meal size, level of stomach fullness and time after feeding. The parameters of the linear model were estimated by maximum likelihood and then applied in a second model to predict the observed mean stomach content. The average gastric evacuation rate of whiting of mean weight 268 g at 10°C was 0.31 g h⁻¹.     

Polyphyly of mtDNA lineages in the Russian sturgeon, Acipenser gueldenstaedtii: forensic and evolutionary implications

Molecular species identification methods are an important component of CITES monitoring programs for trade in sturgeon and caviar. To date, obtaining molecular evidence for distinguishing caviar from four closely related Eurasian sturgeon species Acipenser baerii (Siberian sturgeon), A. gueldenstaedtii (osetra), A. persicus (Persian sturgeon), A. naccarii (Italian sturgeon) remains problematic. Using approximately 2.3 kb of mtDNA sequence data (cytochrome b, NADH5, control region), we find this to be attributable to the polyphyletic nature of these mitochondrial DNA markers in the Russian sturgeon, A. gueldenstaedtii. Two mitochondrial lineages are present within this species: one is phylogenetically affiliated with A. persicus and A. naccarii, while the other clusters with A. baerii. These findings have a direct impact on molecular testing of commercial caviar and demonstrate the necessity of using large sample sizes when constructing forensic databases. Furthermore, the results affect current taxonomic designations for these species as well as hypotheses concerning their evolutionary origins.     

Gastric evacuation rates and daily rations of Arctic cod (Boreogadus saida) at low temperatures

Gastric evacuation rates were determined for different sizes of Arctic cod (Boreogadus saida) at sub-zero temperatures (−1.4 and −0.5°C). These temperatures represent ambient conditions for Arctic cod in the Canadian high Arctic. Evacuation half-times, the time required for half of the content of the stomach to be evacuated, were longer (36–70 h; mean=51 h) than those reported in studies carried out on other fish species. Gastric evacuation rates at low temperatures were equal to, or below, those predicted by extrapolation from experiments conducted at higher temperatures. There were no significant differences in evacuation rates among fish size-groups or diets, but evacuation rates were slower for fish that had been starved prior to experiments. Estimated daily rations for Arctic cod in Resolute Bay, N.W.T., were 0.51% body weight for small fish (4.5 g) and 1.13% body weight for large fish (51 g). Slow stomach evacuation rates at low temperatures may limit daily food intake when food is seasonally abundant. This may contribute to slow growth rates and limited maximum size of Arctic cod in Canadian high Arctic waters. Received: 14 July 1997 / Accepted: 15 November 1997     

Rates of gastric evacuation in piscivorous brown trout, Salmo trutta

SUMMARY. 1. The dry weight of food remaining in the stomachs of piscivorous trout decreased exponentially with time. Gastric evacuation rates increased exponentially with increasing temperature but were unaffected by predator size, meal size or type of fish prey.
2. Mathematical models were developed to estimate both the rate and time for the gastric evacuation of different meal sizes (expressed as dry weight), and were applicable to piscivorous trout of different sizes (length range 10–32 cm) feeding on trout fry or sticklebacks at different temperatures (range 5–18°C).
3. The wet weight of food in the stomachs also decreased exponentially with time, but evacuation rates both increased with temperature and decreased with increasing meal size; the latter relationship occurred because relative rates of water loss from a meal also decreased with increasing meal size. Use of wet or dry weights can therefore lead to different conclusions about the effect of meal size on evacuation rates.
4. When piscivorous trout were fed three consecutive meals of varying size, the models predicted the total dry weight of food left in the stomach, but not the weight remaining for each individual meal. Interactions between meals led to an increase in evacuation rates for meals consumed early in the series and a decrease in evacuation rates for later meals.
5. Evacuation rates for piscivorous trout were compared with those for trout feeding on invertebrates in an earlier study, and were close to those for caddis larvae as prey, higher than those for mealworms and lower than those for a variety of invertebrate prey. Although a great deal is now known about the daily food intake and growth rates of trout feeding on invertebrates, there is little comparable information for piscivorous trout.     

The effects of temperature and meal size on the rate of gastric evacuation in perch (Perca fluviatilis) fed on fish larvae

SUMMARY. The rate of gastric evacuation in perch (Perca fluviatilis) (89–170 mm length) fed on fish larvae was studied at temperatures between 12.0 and 21.7°C. Gastric evacuation rates were usually described by an exponential function. The instantaneous rate of gastric evacuation ( R ) was constant for a large number of different meal sizes. At higher food rations, a lag phase in digestion was found during the first part of digestion, and this ration size was smaller for smaller perch (89–110 mm) than for bigger perch (120–170 mm). Below these larger meal sizes, gastric evacuation was similar for the different size classes studied. The relation between R and temperature was described by an exponential function. The effects of meal size, number of food items, fish size and temperature on the rate of gastric evacuation are discussed.     

Effects of trophic levels (chlorophyll and phosphorous content) in three different water bodies (urban lake,reservoir and aquaculture facility) on gill morphology of Nile tilapia (Oreochromis niloticus)

Histological and ultrastructural analyses of gills were observed in Nile tilapia collected from three different waterbodies in southeast Brazil: an urban lake in a park in the city of São Paulo, a reservoir in a rural city, and a commercial aquaculture facility. These waterbodies were analyzed and classified as hypereutrophic, eutrophic, and supereutrophic, respectively, with 310.00, 94.00, 28.00 of phosphate ( μg L^?1) and 65.49, 24.95, 12.83 of chlorophyll (μg L^?1). A significant difference in the histological alterations index (HAI) was observed only in fish from the urban lake, with the presence of cell hypertrophy, hyperplasia, aneurism, and other alterations. When compared to the other groups, a large quantity of rodlet cells was also observed in the urban group. These results demonstrate the correlation of eutrophic states of water with gill morphology. Also discussed is the premise that large amounts of organic material dissolved in water can alter the morphology of the fish gills.     

The ontogenetic development of the digestive tract and accessory glands of sterlet (Acipenser ruthenus L.) larvae during endogenous feeding

The process of differentiation of digestive tract structures in the sterlet Acipenser ruthenus (L.) larvae was studied from hatching to the beginning of exogenous feeding [9 dph (day post hatching)] using histological procedures. On the day of hatching the digestive tract was closed and completely filled with nutrients (the yolk platelets) that were successively utilized during development. A liver primordium was present in the ventral region of the yolksac. The pancreas was observed on the 2 dph. At the same time, the mouth opening took place. Glandular and nonglandular stomach and anterior and intermediate intestine developed from the yolksac walls. Gastric glands became visible on the 7 dph. The primary intestine developed into the spiral intestine. At the moment of onset of exogenous feeding the yolk material was completely exhausted and there was not mixed feeding observed in sterlet larvae. The fish started exogenous feeding on the 9 dph, which was accompanied with evacuation of melanin plug. At the end of endogenous feeding the digestive tract of sterlet larvae was developed and functional, so they could properly utilize food.     

Rates of gastric evacuation in brown trout, Salmo trutta L.

Brown trout of similar length and weight were fed a standard meal which contained a known number of food organisms of the same size-group and taxon (seven taxa were used). The weight of digestible organic matter in a trout stomach decreased exponentially with time. i.e. at a constant relative rate. At a particular water temperature, the food organisms were either evacuated from the stomach at similar rates (Group 1: Gammarus pulex, Baetis rhodani, Chironomidae, Oligochaetes) or at progressively slower rates (Group 2: Protonemura meyeri, Hydropsyche spp., Tenebrio molitor). Rates of gastric evacuation were not significantly different for food organisms of different size groups of the same taxon, or for different sized meals, or for different sizes of trout (range 20–30 cm), or for mixed and multiple meals (three meals over 16 h). Times are given for the gastric evacuation of 50%, 75%, 90% and 99% of the digestible organic matter in a meal. Starvation periods of 1, 2, 3,4 and 5 days prior to feeding did not affect evacuation rates. The rates were slightly, but not significantly, slower for starvation periods of 6 and 7 days, and were often significantly slower for starvation periods of 10, 15 and 20 days. Evacuation rates increased exponentially with increasing water temperature. It was possible to estimate both the rate and time for the gastric evacuation of different meals at water temperatures between 3–8°C and 19·1°C.     

Gastric evacuation of single and multiple meals by piscivorous coho salmon,Oncorhynchus kisutch

Synopsis Gastric evacuation of multiple meals of recently emerged sockeye salmon, Oncorhynchus nerka, consumed by juvenile coho salmon, O. kisutch, were compared with that expected from a single meal evacuation rate model developed for the estimation of food consumption by coho in the field. Significant interaction occurred between meals consumed two hours apart (p<0.001). Evacuation of the first of two meals (29.9% of initial weight remaining) was significantly faster (p<0.05) than that of a single meal (36.1% of initial weight remaining) after four hours, whereas evacuation of the second meal (72.2% of initial weight remaining) was significantly slower (p<0.001) than that of single meals (50.6% of initial weight remaining) after two hours. The total weight of the multiple meal remaining after four (0.191 g), six (0.138 g) and eight (0.070 g) hours averaged within 6% of that predicted by the single meal evacuation model (0.186 g, 0.115 g and 0.073 g, respectively). These data suggest that the stomach evacuation model based on single meals is adequate for estimating the evacuation of prey consumed by continuously feeding coho salmon.     

Age and growth of the bull shark (Carcharhinus leucas) around Reunion Island,South West Indian Ocean

Sharks exhibit varied demographic strategies depending on both the species and the population location, which make them more or less vulnerable to fishing. Accurate evaluation of local age and growth parameters is therefore fundamental for the sustainable management of their stocks. Although demographic parameters have been assessed for bull shark (Carcharhinus leucas) populations in several locations of the world, this information is missing so far around Reunion Island, in the south-west Indian Ocean. To fill this gap of knowledge, age and growth data were gathered from the vertebrae of 140 individuals of C. leucas (77 females and 63 males, mostly adults) fished around the island between 2012 and 2019. After verification of the annual deposition of growth band pairs on these structures using relative marginal increment analysis on 40 individuals, band pairs were counted along the vertebral centrum for each individual. Thanks to this approach, growth was shown to significantly differ between male and female C. leucas around Reunion Island, with respective von Bertalanffy growth model equations of L_t =  and L_t = . Indeed, the females of the species fished in this area were significantly (P < 0.001) larger than local males, with an estimated difference in size of ~16.1 cm at 20 years old. They also apparently reach older ages, with an estimated maximum age of 33.50 years, against 29.75 years only for the males. The estimated size at birth around the island is larger than elsewhere in the world, varying from 92.30 to 100.00 cm depending on the method used. These results confirm that the population of C. leucas around Reunion Island exhibits a K-selected strategy, which makes it highly vulnerable to fishing pressure.     

Demogenetic structure of brown trout Salmo trutta Linnaeus, 1758 populations in mountain headwaters: implications for conservation management

A demogenetic analysis based on 7 years of observation (2005–2011) was conducted to examine the population structure of brown trout Salmo trutta in pristine dendritic headwaters. The value of genetic divergence (F_ST) among sampling units ranged from ?0.03 to 0.16. Demographic synchrony was low or moderate, and the average correlation coefficient of population growth between sampling units () ranged from 0.28 to 0.66. No isolation by distance was observed, but genetic divergence was negatively correlated with demographic synchrony among sampling units. Variance in the population growth rate (i.e. local extinction probability) increased with distance from the mainstream and from other sampling units. In contradiction with the usual model of stream‐dwelling salmonids, the upstream sections of headwaters holds only ephemeral subpopulations, whereas the mainstream played a role in the source area of the metapopulation. These findings stress the importance of the mainstream in management conservation for brown trout in low productive mountain headwaters.     

Formulation of Controlled-Release Capsules of Biopharmaceutical Classification System I Drugs Using Niacin as a Model

Vitamin B₃ is made up of niacin (nicotinic acid) and its amide, niacinamide. Both have equivalent vitamin activity, but only niacin (not niacinamide) is effective in lowering elevated low-density lipoprotein cholesterol and triglyceride levels in the blood. Administration of an extended-release (ER) oral tablet would frequently encounter food. If hydrogel is used to formulate the matrix of a biopharmaceutical classification system I drug (high solubility and high permeability), the dosage form absorbs water and swells.. The softened outer layer may be slashed off by food present in the stomach, thus, exposing the core tablet more readily for water absorption and speeding up drug release from its original designed rate. This project aimed to formulate niacin CR pellets made of hydrophobic inert matrix. After niacin was melted with excipients and cooled, the mass was extruded and spheronized into pellets. Size distribution and flowability were determined before pellets were filled into hard gelatin capsule. The USP dissolution study revealed that a candidate formulation of 250 mg in strength released similar amount of niacin as its commercial reference, niacin controlled-release 500 mg tablet, in 6 h (223.9 ± 23.8 mg, n = 4 versus 259.4 ± 2.6 mg, n = 3). The differential scanning calorimetry study of the pellets in capsules stored in 40°C for 4 weeks, and the content assay of capsules in 40°C up to 6 months suggested that niacin was stable within the innovative formulation. In vitro release from this innovative ER capsules stored at 40°C up to 4 weeks were also investigated.     

Comparative morphology of the pectoral fin spine of the Persian sturgeon Acipenser persicus,the Russian sturgeon Acipenser gueldenstaedtii,and the Starry sturgeon Acipenser stellatus in Iranian waters of the Caspian Sea

The morphological characteristics of the pectoral fin spine were compared in three species of sturgeon, the Persian sturgeon (Acipenser persicus), the Russian sturgeon (Acipenser gueldenstaedtii), and the Starry sturgeon (Acipenser stellatus), all sampled from the Caspian Sea. On the basis of morphological characters of the pectoral fin spine, 62.2% of the individuals were correctly classified into separate groups. The cluster analysis also divided the three species into two major subgroups. Acipenser persicus and A. gueldenstaedtii were grouped together, suggesting a similar evolutionary basis. Significant morphological heterogeneity in pectoral fin spine characteristics was observed among the three sturgeon species. Principal component analysis identified the largest differences were in the pectoral fin spine size and the angle between distal pectoral fin spine and the horizontal line (A°). The first and second principal components (PC1 and PC2) of all observations accounted for 64.19% and 14.33% of the total variation, respectively. The combination of all analyses showed the relevance of applying pectoral fin spine shape for interspecific distinction of the three species of sturgeons.     

A Noninvasive Technique for Determining Sex of Live Adult North American Sturgeons

We have developed a noninvasive technique to determine the sex of adult North American sturgeon by examination of the external morphology of live individuals. We analyzed four sturgeon species taken by commercial and scientific harvest: white Acipenser transmontanus, green A. medirostris, Atlantic A. oxyrinchus and shortnose A. brevirostrum. Males have a urogenital opening in the shape of a letter Y, while the opening of females is in the shape of the letter O. We accurately sexed 26 of 36 sturgeon using this criterion. Accuracy was highest in live fish (82%), and significantly lower in dead fish (29%). Dead sturgeon usually have the rectum prolapsed so that the urogenital opening is protruded, and thus making the sexes indistinguishable.     

Effects of pre- and post-prandial starvation on meal size and evacuation rate of juvenile Atlantic salmon, Salmo salar L.

After a pre-prandial period of starvation or feeding with unlabelled food, 0+ salmon parr (0.8–11.7 g) were fed a test meal of iron particle labelled food and subsequently were again either starved or fed unlabelled food. The quantity of labelled food consumed and the evacuation rate was determined by serial radiographs. In fish of all sizes, pre-prandial starvation causes a larger test meal (as a percentage of body weight) to be consumed when compared to pre-prandially fed fish. In addition, pre-prandial starvation results in relatively larger meals as a percentage of body weight being taken by smaller compared to larger fish. This result was not evident for pre-prandially fed fish. Evacuation rate was unrelated to body size irrespective of feeding history. Post-prandial starvation decreased evacuation rate but this effect was inversely related to the quantity of food consumed. Larger meals were not evacuated differently from smaller meals if feeding occurred post-prandially, irrespective of pre-prandial starvation.     

Diet of farm‐escaped sturgeon in the Yangtze River

The diet of farm‐escaped sturgeon accidentally introduced into the Yangtze River ecosystem was investigated from samples collected over 10 days. The fish had consumed adequate quantities of natural food, with prey type related to fish body size. The fish were categorized according to their primary dietary component: demersal fish were most common prey of kaluga Huso dauricus and H. dauricus × Acipenser schrenckii hybrids of total length 120.3–188.7 cm. Shrimp Macrobrachium nipponensis made up the major portion of the diet of H. dauricus × A. schrenckii and Acipenser baerii × A. schrenckii of total length 91.1–106.8 cm. Gammarid amphipods were consumed by A. baerii × A. schrenckii of total length 35.0–81.2 cm. The body length of prey was proportional to the fork length of the sturgeon, Y = 0.19X‐9.46, R² = 0.997. Escaped sturgeon had travelled at least 898 km downstream from the point of escape in the Yangtze River and were feeding on native macrobenthos and demersal fish.     

Estimating occupancy of Chinese pangolin (Manis pentadactyla) in a protected and non‐protected area of Nepal

Chinese pangolin is the world's most heavily trafficked small mammal for luxury food and traditional medicine. Although their populations are declining worldwide, it is difficult to monitor their population status because of its rarity and nocturnal behavior. We used site occupancy (presence/absence) sampling of pangolin sign (i.e., active burrows) in a protected (Gaurishankar Conservation Area) and non‐protected area (Ramechhap District) of central Nepal with multiple environmental covariates to understand factors that may influence occupancy of Chinese pangolin. The average Chinese pangolin occupancy and detection probabilities were  ± SE = 0.77 ± 0.08;  ± SE = 0.27 ± 0.05, respectively. The detection probabilities of Chinese pangolin were higher in PA (  ± SE = 0.33 ± 0.03) than compared to non‐PA (  ± SE = 0.25 ± 0.04). The most important covariates for Chinese pangolin detectability were red soil (97%), food source (97.6%), distance to road (97.9%), and protected area (97%) and with respect to occupancy was elevation (97.9%). We recommended use of remote cameras and potentially GPS collar surveys to further investigate habitat use and site occupancy at regular intervals to provide more reliable conservation assessments.