Juvenile Diet Research Articles

Pea protein concentrate in diets for sharpsnout sea bream (Diplodus puntazzo): effects on growth and health status

ABSTRACTFour diets for sharpsnout sea bream juveniles (14 g body weight) with four levels of air-processed pea protein concentrate (PPC) (0, 160, 320 and 487 g/kg diet) were tested in triplicate. The experimental diets were isonitrogenous (43% crude protein) and isolipidic (19% ether extract) and the fish were fed to satiation twice a day. After 125 d, fish growth was diminished by the inclusion of PPC. Feed conversion did not show significant differences in any treatment. Neither the body analyses nor the protein and individual essential amino acid retention efficiencies were affected by the inclusion of PPC in the diet. However, histological gut examinations revealed noticeable differences. Fish fed the diet with the highest inclusion level of PPC presented the longest villous length and the most goblet cells, and the width of the lamina propria increased in the anterior intestine. Although no negative changes in nutritive parameters were detected, these alterations might affect nutrient transport, with negative consequences for fish growth. It was concluded that the PPC in the amounts tested here is an inappropriate substitute for fishmeal in diets for sharpsnout sea bream juveniles.

Effect of partial replacement of fishmeal with Eichhornia crassipes on growth and survival of Labeo rohita (Hamilton, 1822) juveniles

The objective of the study was to find out the effect of partial replacement of fish meal in the diet of Labeo rohita juveniles. In this experiment, the data pertaining to growth, survival rate, feed conversion ratio, protein efficiency ratio of L. rohita at partial replacement of fishmeal with E. crassipes were evaluated. For that purpose fry of approximately equal weight (57.97mg ± 1.25) were distributed in groups of 15 to each four aquaria at 0% (T1), 10% (T2), 20% (T3), 30% (T4) and 40% (T5) inclusion levels of aquatic macrophyte, Eichhornia crassipes. Maximum mean weight gain (235.25 ± 11.04 mg) was observed in T1 and minimum (165.06 ± 10.93 mg) was observed in T5 at the end of the experiment. Among the treatments tested, the highest survival (89.99% ± 1.93) was recorded in treatment T1 and minimum was found in T4 (79.99% ± 2.72). Lowest FCR was recorded in treatment T3 (2.02 ± 0.39) and highest was found in T5 (3.08 ± 0.59). Higher SGR was observed in treatment T1 (297.15 ± 18.78%) and minimum was observed in T5 (182.74 ± 18.45%). The study revealed a decrease in the growth performance indices as the percentage of water hyacinth increases. In present study also there was not much difference in growth rate upto 20% incorporation of E. crassipes in the diet. Also, significant difference was observed among treatments with respect to feed utilization (P<0.05).

The effects of fish hydrolysate and soy protein isolate on the growth performance, body composition and digestibility of juvenile pike silverside, Chirostoma estor

An experiment was carried out to evaluate the effect of the use of a fish hydrolysate, CPSP Special-G™ (FH) and a soy protein isolate, SUPRO-590™ (SPI) in balanced diets, on growth performance, survival, body composition and nutrient digestibility in juvenile Pike Silverside, Chirostoma estor. Eight isonitrogenous diets (410gkg−1): three with different substitution levels of FH (15, 30 and 45%), three with different substitution levels of SPI (15, 30 and 45%), a diet with a combination of both products (15%FH/15%SPI) and a control diet (0% FH, 0%SPI), were prepared. Juvenile fish (1376±58mg initial weight) were fed the eight diets three times a day, for eight weeks. Best growth was obtained in fish fed control diet and diets with an inclusion of 15% of both products alone or in combination (FH15, SPI15 and FH15/SPI15) (P<0.05). Juveniles fed diet FH45 showed the lowest survival (P<0.05) and there is a trend to decrease survival of juveniles with the increasing levels of SPI. As a general trend, the fish fed SPI showed better survival than fish fed FH. In the case of fish body protein composition, no significant differences were obtained (P>0.05) at the end of experiment. Dry matter, protein, lipid and energy digestibility (ADC) were influenced by ingredient type and inclusion level. There was a trend to decrease dry matter and protein ADC with increasing levels of SPI. Under the experimental conditions, the two products tested can be used separately or combined at inclusion levels up to 15%, without affecting fish growth and survival. Incorporation of 30 or 45% of either product could cause a detrimental effect on juvenile fish growth. This suggests that FH and SPI are viable protein sources at inclusion levels up to 15% in diets for juveniles of this species.

Ontogenetic shifts in the diet of plains hog-nosed snakes (Heterodon nasicus) revealed by stable isotope analysis

Wild snake diets are difficult to study using traditional methods, but stable isotopes offer several advantages, including integrating dietary information over time, providing data from individuals that have not fed recently, and avoiding bias towards slowly-digesting prey items. We used stable isotope signatures of carbon and nitrogen from scale tissue, red blood cells, and blood plasma to assess the diet of wild plains hog-nosed snakes (Heterodon nasicus) in Illinois. We developed Bayesian mixing models which, taken together, predicted that H. nasicus shifted from a juvenile diet predominantly (31–63%) composed of six-lined racerunners (Aspidoscelis sexlineatus) and their eggs to an adult diet predominantly (44–56%) composed of eggs of the aquatic turtles Chrysemys picta and Chelydra serpentina, with a contribution from toads (Anaxyrus sp.; 6–27%) during their adolescent years. These results agreed with sparse data from gut contents. Combining traditional and isotopic techniques for studying the diets of wild snakes can increase the utility of both types of data.

Feeding habits of Mesoclemmys vanderhaegei (Testudines: Chelidae)

We studied the feeding habits of Mesoclemmys vanderhaegei in small water bodies in the central region of the Brazilian Cerrado. We captured 80 individuals, 79 of which [41 (52%) females, 27 males (34%), 11 (14%) juveniles] had stomach contents for analysis . We identified 64 food item categories. The turtles were eating more animal than plant material, aquatic invertebrates being the most conspicuous diet item found. Plant material was more abundant in females and rare in the diet of juveniles. Mesoclemmys vanderhaegei proved to be an omnivorous and opportunistic chelonian, feeding on a wide range of food items. Although there are differences in the consumption of food items among sexes and age categories, the most consumed food categories were common in all water bodies sampled.

Evaluation of Potential Feed Ingredients for the Juvenile Four‐sided Sea Cucumber, Isostichopus badionotus

AbstractThe objective of this study was to evaluate two seaweed species, Solieria filiformis and Macrocytis piryfera, both as dry‐meal powder and predigested meal, to be used as ingredients in artificial diets for the juvenile four‐sided sea cucumber, Isostichopus badionotus. Four diets were tested in triplicate: S. filiformis dry‐meal powder and predigested meal and M. piryfera dry‐meal powder and predigested meal, mixed with 70% of beach sand. Survival exceeded 90% in all the treatments, and there were no differences in the growth of juveniles using dry‐meal powder or predigested meal. Weight gain was calculated for all the diets, and the highest values were obtained by animals fed S. filiformis. No differences between using dry‐meal powder and predigested meal were found, so these diets were excluded from the second trial. The ingestion rate was the same with both algae, but the feed conversion ratio was twice as high for M. piryfera. Solieria filiformis exhibited a number of differences in fatty acid and amino acid profiles, including higher proline, arginine, and saturated fatty acid levels. The results indicate that S. filiformis has better nutritional characteristics to be an ingredient for an artificial I. badionotus juvenile diet.

Assessment of cotton-seed (&lt;i&gt;Gossypium&lt;/i&gt; species) meal as ingredient in the diet of &lt;i&gt;Clarias gariepinus&lt;/i&gt; juveniles

The effect of feeding graded levels of cotton GossypiumSpp . seed meal as an inclusion in the diet of Clariasgariepinus juveniles for growth performance was analysed in comparison with the conventional commercial fish feed. Six experimental rations formulated were cotton-seed Gossypium spp . meal replaced fish meal at graded levels of 20%, 30%, 40% 50%, and 100% and were fed to Clarias gariepinus juveniles for 56 days. The experiment was conducted in six outdoor concrete tanks in the Department of Biological Sciences Garden, Ahmadu Bello University, Zaria, Nigeria. Data for each parameter were subjected to Analysis of Variance (ANOVA) and the means for various experimental diets were compared for significant differences at 0.05% level of inclusion. The results showed that fish fed with diet contained 20% cottonseed meal (D 1 ) gave the best Body Weight Gain (81.28g), Specific Growth Rate (2.23), and Condition Factor (1.49), while diet contained 30% cottonseed meal (D 2 ) gave the least Weight Gain (49.67g), Specific Growth Rate (1.58) Conversion Ratio (3.64) and Condition factor (0.79). The results were significantly different (p<0.05) for both growth and feed utilization parameters. Therefore, cotton-seed meal can be used as a replacement for fish meal at 20% level of inclusion. The results established significant reduction in production cost while optimal production is achieved. Keywords : Cotton-seed ( Gossypium species ), Diet, Growth performance, Clarias gariepinus juveniles

An evaluation of mixture of Moringa (&lt;i&gt;Moringa oleifera&lt;/i&gt;) leaf and kernel meals as partial replacement for fish meal in the diet of &lt;i&gt;Clarias gariepinus&lt;/i&gt; juveniles

A 56-day feeding trial was conducted to evaluate the growth performance and nutrient utilization of Clarias gariepinus juveniles fed graded levels of a mixture of Moringa oleifera leaf and kernel meal (1:1) as partial replacement for fishmeal. Triplicates groups of fish (average weight, 8.83±0.04 g) were allotted to four isonitrogenous (40% crude protein) diets containing mixture of M. oleifera leaf and kernel meal (1:1) at 0%, 20%, 40% and 60% designated as CD, 20RM, 40RM and 60RM respectively. At the end of the feeding trial, weight gain and specific growth rate of the groups of fish reared on CD and 20RM were statistically higher (P&lt;0.05) than those reared on 40RM and 60RM diets. The protein efficiency ratio of CD and 20RM were statistically better (P&lt;0.05) than those of 40RM and 60RM. The results showed that the mixture of M. oleifera leaf and kernel meal (1:1) can be used to replace up to 20% of the fish meal in C. gariepinus juvenile diet, without adverse effects on survival, growth performance and nutrient utilization.Keywords: Moringa leaf, moringa kernel, growth performance, nutrient utilization, Clarias gariepinus

Food Habits of Invasive Bullfrogs and Native Thin-Toed Frogs Occurring in Sympatry in Southeastern Brazil

Abstract. Although the feeding ecology of sympatric anurans has been studied, less is known about the food habits of co-occurring invasive and native frog species, particularly in the Neotropics. We compared the food habits of invasive bullfrogs (Lithobates catesbeianus) and native thin-toed frogs (Leptodactylus cf. latrans) in a locality of Southeastern Brazil. Monthly field surveys and stomach content analyses were performed between September 2008–April 2009 and September–November 2009. Prey items were identified to the lowest taxonomic level and diet overlap was estimated. Juveniles of both species had similar body sizes, but adult thin-toed frogs were smaller than adult bullfrogs. Insects and spiders dominated the diets of juveniles of both species and of adult thin-toed frogs, whereas anurans and water bugs predominated in adult bullfrog diets. Thin-toed frogs consumed a larger number of prey items than bullfrogs, which in turn consumed more voluminous prey items. Aquatic and amphibious prey items we...

Evaluation of soybean meal replacement with sesame seed meal using activated charcoal as an additive in the diet of African catfish juveniles, Clarias gariepinus

This study evaluated the effects of 0.25% activated charcoal added to sesame seed meal (SSM) in partial replacement of soybean meal (SBM) of juvenile Clarias gariepinus diet on growth and haematological parameters for 70 day experimental period. Six experimental diets were formulated as: control diet 1 (100% SSM without activated charcoal), control diet 2 (100% SSM plus 0.25% activated charcoal), diet 3 (50% SMB+50% SSM), diet 4 (50% SBM+50% SSM+0.25% AC), diet 5 (30% SBM+70% SSM) and diet 6 (30% SBM+70% SSM+0.25AC). The inclusion of activated charcoal recorded significant improvement in mean weight gain, mean feed intake, specific growth rate (SGR), protein intake (PI) and protein efficiency ratio (PER). The control diet 2 recorded the highest values for growth and nutrient utilization parameters while diet 5 recorded the least values for these parameters. The best values for mean weight gain (65.33±5.57 g), specific growth rate (2.56±0.12% / day) and feed conversion ratio (0.71±0.05) were recorded in fish fed control diet 2 while the worst values (41.30±3.82 g, 1.92±0.11% / day, and 1.07±0.07, respectively) for these parameters were observed with diet 5. However, haematological parameters did not differ significantly across the diets. Thus, from this study 0.25% activated charcoal could favorably be added to the feed of C. gariepinus for optimum performance without any adverse effect on the health status of the fish.

Combined effects of dietary mannan oligosaccharides and Pediococcus acidilactici and their combination in low fish meal and fish oil diets for European sea bass, Dicentrarchus labrax, juveniles

Low dietary levels of raw marine ingredients in marine fish species diets induce variable side-effects on fish growth performance, welfare and health, depending mainly on the terrestrial protein and oil source used, dietary levels and fish species studied. Particularly, high dietary levels of vegetable meals (VM) and oils (VO) blends, may induce intestinal dysfunction by altering tissue morphology, intestinal functionality, microbiota populations or gut associated lymphoid tissue (GALT) homeostasis. On the other hand, alternative feed ingredients such as prebiotics and probiotics have demonstrated to promote fish performance and disease resistance through potentiating GALT efficiency and functionality. Thus, the main objective of this study is to evaluate the effects of dietary mannan oligosaccharides (Biomos® and ActigenTM), Pediococcus acidilactici (BAC; Bactocell ®) and their combination in low FM and FO diets for european sea bass juveniles. Fish of 19.7±0.09g were distributed in 18 tanks and fed for 90 days six experimental diets with a low content of FM and FO, containing graded and combined levels of MOS and BAC as follows: HP; LP; B; HPB; LPB and C (Control). After 60 and 90 days of feeding, fish were sampled for growth, gut morphometry and histopathology, gut mucus production and expression of GALT related genes. Besides, samples were taken for gut iNOS and TNFα immunohistochemistry (IHQ) and for in situ hybridation (ISH) studies of MHCβ, TCRβ, CD4 and CD8. Fish fed diets HP, LP and LPB presented higher final weight. Two-way ANOVA attributed this effect to MOS regardless of dietary BAC inclusion. The use of prebiotic induced an increase on number of goblet cells in posterior gut (Fig.1). IHQ analyses performed against iNOS and TNFα showed the use of prebiotics induce an inflammatory-like pattern in the apical side of gut villi. Results for ISH showed that combined use of pre and probiotic induced a wider distribution of TCR-β marked cells, with special emphasis in the lamina propria. Expression of GALT-related genes, will be also discussed. Fig.1. Posterior gut (Alcian Blue-PAS). (a) LPB and (b) C diets t=90days. Note the higher number of goblet cell for fish fed LPB diet Acknowledgements: This study has been funded by the Spanish Ministry of Economy and Competitiveness, Project AGL2012-39919 (PROINMUNOIL)

Early Ocean Life History of Harrison River Sockeye Salmon and their Contribution to the Biodiversity of Sockeye Salmon in the Fraser River, British Columbia, Canada

AbstractDuring a study of the early marine survival of Chinook Salmon Oncorhynchus tshawytscha and Coho Salmon O. kisutch in the Strait of Georgia from 1998 to 2010, moderate abundances of juvenile Sockeye Salmon O. nerka were observed to remain in the strait much longer than previously thought. In 2008, DNA stock identification showed that these juveniles were from the Harrison River, a population with a sea‐type life history in which juveniles enter the ocean during the year of emergence from the gravel. Using information collected in 1998–2010, we describe the early ocean life and production of Harrison River sea‐type Sockeye Salmon. Juveniles entered the Strait of Georgia from the Fraser River over an extended period, with most entering after mid‐July—about 8 weeks later than lake‐type juveniles, which had virtually all left the strait by that time. The September diets of sea‐type juveniles were highly selective for hyperiid amphipods, which were not abundant in the zooplankton. Interaction with juvenile Pink Salmon O. gorbuscha during this early marine period was identified as potentially affecting the age structure of returning adults. Juvenile Sockeye Salmon remained in the strait until the fall and then moved offshore, where they remained until returning as age‐3 or age‐4 adults. There was a strong positive relationship between the September CPUE of juveniles in the Strait of Georgia and the total adult return of Harrison River Sockeye Salmon, indicating that total production in recent years was likely related to conditions in the strait. From 2005 to 2011, Harrison River Sockeye Salmon production exhibited a large increase in comparison with the total production of Sockeye Salmon in the Fraser River system. This recent increase in production of late‐ocean‐entering juveniles with a sea‐type life history identifies the importance of managing for biodiversity of Sockeye Salmon populations within the Fraser River drainage.Received April 28, 2015; accepted November 17, 2015

PNA クランピングを用いたヒラメ稚魚と稚アオリイカにおける食性解析の試み

PNA クランピングを用いたヒラメ稚魚と稚アオリイカにおける食性解析の試み

茨城県北浦の沖帯から沿岸帯におけるヌマチチブ仔稚魚の生息場所利用と食性

茨城県北浦の沖帯から沿岸帯でヌマチチブ仔稚魚の分布と移動および食性を調査した。孵化後数日以内の上屈前仔魚は沖帯の表・中層に分散し，浮遊期稚魚は沖帯の底層に集群した。着底期から底生期の稚魚は沖帯から沿岸帯へと移動した。この接岸移動に伴い，稚魚の主要な餌は動物プランクトンから底生性餌料へと変化した。沿岸帯での底生期稚魚の個体数密度と各環境要因との関係を一般化線形モデルで解析したところ，ヨシ根元のえぐれの奥行と泥分が上位モデルで選択され，本種の底生期稚魚の成育場としてヨシ帯が重要であることが示された。

THE USE OF GARLIC (Allium sativum) MEAL AS A NATURAL FEED SUPPLEMENT IN DIETS FOR EUROPEAN SEABASS (Dicentrarchus labrax) JUVENILES

The incorporation of garlic meal (GM) in diets for European seabass juveniles were evaluated with a diet containing 43% protein and 17% lipid (gross energy 19kJ/g diet). Experimental diets with GM incorporation of 0, 2, 4, and 6% were fed to fish (10.60 ±0.16 g) until satiation for 60-days. Significant differences ( p<0.05 ) were recorded for growth performance, with the highest rate in the 4% GM group, followed by the control group. Improved feed conversion (FCR) and protein efficiency rates (PER) were observed in the GM4 group compared to the other treatments. Nitrogen retention as a percent of intake was highest in the in GM4 group. Significantly higher values ( p<0.05 ) were found for body protein and lipid, and lower values ( p<0.05 ) for the hepatosomatic, viscerasomatic or mesenteric fat indexes in the GM4 group compared to the other treatments. Fish fed garlic supplemented diets showed lower saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA), but higher polyunsaturated fatty acids (PUFA) compared to the control group with no garlic treatment. Results indicate that dietary GM inclusion of 4% can improve fish growth and nutrient utilization with an increase of fish muscle quality by elevated PUFA concentrations, and a reduction of total nitrogen excretion.

Substituição do milho pelo sorgo em dietas para juvenis de pacu

Resumo: O objetivo deste trabalho foi avaliar o coeficiente de digestibilidade aparente (CDA) de sorgo, e determinar o desempenho produtivo, os índices somáticos, os parâmetros hematológicos e a composição centesimal do filé de pacus alimentados com dietas com diferentes níveis de sorgo, além de avaliar o custo da formulação. Para a determinação do CDA da matéria seca (MS), da proteína bruta (PB), do extrato etéreo (EE) e da energia bruta (EB) do sorgo, utilizaram-se 160 pacus, com peso médio de 56,00±8,04 g, alimentados com dieta-referência e dieta-teste (30% sorgo), acrescidas de 0,1% de óxido de cromo III. Para avaliação do desempenho, utilizaram-se 180 juvenis de pacu (10,80±0,77 g) alimentados com cinco dietas experimentais, em que 0, 25, 50, 75 e 100% da energia do milho foi substituída pela do sorgo. Os CDA do sorgo pelo pacu foram: 78,52% da MS; 74,82% da PB; 94,36% de EE; e 77,24% de EB. Não se observaram diferenças entre as dietas quanto ao desempenho, aos índices somáticos e aos parâmetros hematológicos. Porém, na composição centesimal dos filés, houve diferença entre os tratamentos. O sorgo apresenta CDA semelhante ao do milho e pode substituí-lo integralmente em dietas para juvenis de pacu, além de diminuir o custo da formulação.

Effect of short chain fructooligosaccharides (scFOS) on immunological status and gut microbiota of gilthead sea bream (Sparus aurata) reared at two temperatures.

The effects of dietary short chain fructooligosaccharides (scFOS) incorporation on hematology, fish immune status, gut microbiota composition, digestive enzymes activities, and gut morphology, was evaluated in gilthead sea bream (Sparus aurata) juveniles reared at 18°C and 25°C. For that purpose, fish with 32g were fed diets including 0, 0.1, 0.25 and 0.5% scFOS during 8 weeks. Overall, scFOS had only minor effects on gilthead sea bream immune status. Lymphocytes decreased in fish fed the 0.1% scFOS diet. Fish fed the 0.5% scFOS diet presented increased nitric oxide (NO) production, while total immunoglobulins (Ig) dropped in those fish, but only in the ones reared at 25°C. Red blood cells, hemoglobin, bactericidal activity and NO were higher at 25°C, whereas total white blood cells, circulating thrombocytes, monocytes and neutrophils were higher at 18°C. In fish fed scFOS, lymphocytes were higher at 18°C. Total Ig were also higher at 18°C but only in fish fed 0.1% and 0.5% scFOS diets. No differences in gut bacterial profiles were detected by PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) between dietary treatments. However, group's similarity was higher at 25°C. Digestive enzymes activities were higher at 25°C but were unaffected by prebiotics incorporation. Gut morphology was also unaffected by dietary prebiotic incorporation. Overall, gut microbiota composition, digestive enzymes activities and immunity parameters were affected by rearing temperature whereas dietary scFOS incorporation had only minor effects on these parameters. In conclusion, at the tested levels scFOS does not seem worthy of including it in gilthead sea bream juveniles diets.

Unrefined Peanut Oil as a Lipid Source in Diets for Juveniles of Two‐banded Seabream Diplodus vulgaris

AbstractA feeding study with Two‐banded Seabream Diplodus vulgaris was conducted to determine the effects of replacement of fish oil (FO) by unrefined peanut oil (PO) on growth performance, feed utilization, body composition, fatty acid composition, and serum biochemical and hematological variables. Three isonitrogenous (35.8%) and isoenergetic (21.15 kJ/g) diets were formulated by replacing dietary FO with PO at levels of level 0% (PO0), 50% (PO50), or 100% (PO100). Fish were fed twice a day until satiation for an experimental period of 8 weeks. The best growth performance was observed in fish fed with the PO0 and PO50 diets. A significant increase was observed in hematocrit and mean corpuscular volume levels of fish fed with PO50 diet compared with the other groups. Hemoglobin, mean corpuscular hemoglobin, total protein, albumin, and globulin were not affected by dietary PO treatment and did not differ among experimental groups. The glucose level was highest in the PO100 group. Triglyceride and cholesterol levels were lower in fish fed diets with PO inclusions than in those fed the control diet. The fatty acid composition of fish was significantly affected by the experimental diets. Glutamic oxaloacetic transaminase, glutamic pyruvictransaminase, lactate dehydrogenase, and alkaline phosphatase were not affected by dietary PO treatment. The n‐3:n‐6 ratio in fish fed the PO0 diet was also higher than in fish fed the PO‐supplemented diets. The results of the present study showed that FO could be substituted by PO up to 50% in Two‐banded Seabream diets without any negative effect on growth performance or serum biochemical and hematological features.

Substituição do milho pelo farelo de algaroba (Prosopis juliflora) em dietas para juvenis de tilápia do Nilo cultivados em baixa temperatura

The objective of this study was evaluating mesquite meal as a substitute for corn in diets for Nile tilapia juveniles. Four isoproteic (34% crude protein) and isocaloric (3,150 kcal kg-1 digestible energy) diets were formulated corresponding to replacement levels (0, 33, 66 and 100%) of corn by mesquite meal. Two hundred and forty tilapia juveniles (1.55 ± 0.02 g) were housed in circular tanks (20 fish per tank of 310 L) in a completely randomized experimental design (n = 3). Fish were fed to apparent satiation three meal per day (8:30 a.m., 12:30 p.m. and 4:30 p.m.) for 70 days. Because low water temperature (23.8 ± 1.2 °C), was registered low growth and feed efficiency of fish at experiment. Tilapia juveniles weight gain, feed intake, specific growth rate and body composition were similar (P > 0.05) in all treatments. Survival increased linearly (P < 0.05) with increasing whole mesquite meal levels in diets. Mesquite meal can completely replace corn in Nile tilapia juvenile diets during periods of low water temperature.

Feeding ecology of two sympatric species of Acetes (Decapoda: Sergestidae) in Panguil Bay, the Philippines

Sergestid shrimps of the genus Acetes are important in global shrimp fisheries and nearshore food-webs. The feeding habits of the sympatric species Acetes erythraeus and A. intermedius from Panguil Bay, Philippines were studied using gut contents and stable isotopes analyses. Both species are omnivorous suspension feeders of plankton, macrophyte detritus, and amorphous particulate organic materials. However, the diet of adults and juveniles differed by prey type. Gut fullness differed over 24h with a night-time peak in A. erythraeus and morning and midnight peaks in A. intermedius. Over 1 year gut fullness peaked during July to September for both species, with a minor peak during January for A. intermedius. Stable isotope analysis revealed similar δ15N values, but both species showed ontogenetic and interspecific separation of δ13C. A. erythraeus seemed to assimilate highly depleted carbon food sources by mangrove-based detrital and plankton trophic pathways, whereas A. intermedius relied on plankton and macroalgal and seagrass detrital pathways. These trophic differences may be mechanisms of partitioning the feeding niche, but allotopy in the two species with A. erythraeus confined to more brackish waters and A. intermedius dwelling in more saline marine waters may indicate that habitat niche segregation underlies these contrasting carbon trophic pathways.