Notemigonus Research Articles

Using stable isotopes and a multiple-source mixing model to evaluate fish dietary niches in a mesotrophic lake

Christensen, D.R. and B.C. Moore. 2009. Using stable isotopes and a multiple-source mixing model to evaluate fish dietary niches in a mesotrophic lake. Lake Reserv. Manage. 25:167–175. We used stable isotope analysis (SIA) of δ13C and δ15N and a multiple-source mixing model to evaluate dietary niches within the Twin Lakes, Washington, fish community to identify potential for exploitative competition, resource partitioning, and predation. The SIA revealed distinct spatial feeding niches; pelagic species were δ13C depleted, while littoral organisms were δ13C enriched. Trophic feeding niches were identified from δ15N enrichment with each successive trophic level. We found δ15N progression with increasing largemouth bass size, suggesting ontogenetic diet variability. Model results suggested that the smaller bass (i.e., ⩽299 mm length) fed principally on golden shiner, crayfish, and macroinvertebrates while larger bass (⩾300 mm) primarily consumed brook trout and golden shiner. Isotopic signatures for golden shiner were intermediary, indicating both pelagic and littoral feeding sources, including phantom midges (nocturnal and pelagic) and damselflies (littoral) as principal diet sources, suggesting possible horizontal diel migration in golden shiner. Pelagic zooplankton was indicated as the most important food source for rainbow trout. Food resources appeared to be partitioned among the Twin Lakes fish community, possibly limiting competitive interactions. Piscivory in largemouth bass was focused on golden shiner and brook trout, suggesting possible top-down regulation of lower trophic levels. Stable isotope analysis and multiple-source mixing models are useful tools that can improve lake and fishery management decisions by providing data on food web dynamics such as competition, resource partitioning, and predation in lakes.

Characteristics of Baitfish Retailers in Kentucky: Evidence of a Market to Support a Regional Industry

Bait shops in Kentucky and surrounding states rely primarily on large-scale suppliers for baitfish. However, these suppliers provide specific species and sizes of fish. This creates a potential market where small-scale producers could supply bait shops with uncommon species and size combinations of baitfish. This study describes baitfish and bait crayfish marketing parameters in Kentucky by reporting results of a survey that elicited marketing information from local baitfish dealers. The results showed 94% of the respondents were interested in purchasing baitfish from local producers. The types of baitfish wanted by these bait dealers from local suppliers included rosy red minnows (Pimephales promelas), catfish (Ictalurus punctatus), and large golden shiners (Notemigonus crysoleucas). The survey provided evidence of significant niche marketing opportunities in baitfish in states such as Kentucky, where baitfish production is not a major industry.

Effects of Loading Density on Golden Shiner Survival during and after Hauling

AbstractFour hauling trips of approximately 6 h each were conducted to investigate effects of loading density on survival of golden shiners Notemigonus crysoleucas. Commercially graded golden shiners (mean weight ± SE, 3.3 ± 0.04 g) were transported at densities of 120, 180, and 240 g of fish/L of water in insulated hauling tanks that were filled with fresh well water, chilled with unchlorinated block ice, and aerated with pure oxygen. The criterion for determining success or failure was golden shiner survival. Transportation at a given density was deemed successful if survival both at trip's end and at 18 h postdelivery was at least 99%. At all three hauling densities evaluated, survival exceeded 99% both at trip's end and at 18 h postdelivery. Furthermore, increasing loading density had no effect on whole‐body cortisol concentrations, demonstrating that no significant stress response occurred. Un‐ionized ammonia concentration increased with loading density (range, 0.05–0.46 mg/L) but had no effect on fish survival. Results of this study indicate that golden shiners can be successfully (≥99% survival) transported for up to 6 h at a density of 240 g/L in well water chilled with unchlorinated block ice and aerated with pure oxygen. Higher loading densities could mitigate the effect of escalating transport cost for commercial farmers.

Effects of Dietary Lipid Concentration, a Dairy–Yeast Prebiotic, and Fish and Nonfish Protein Sources on Growth, Survival, and Nonspecific Immune Response of Golden Shiners in Indoor Tanks and Outdoor Pools

AbstractWe conducted two feeding trials in which golden shiners Notemigonus crysoleucas were given six practical diets: Two basal diets with 5% fish meal and either 4% or 10% supplemental lipid (poultry fat [PF]); two prebiotic diets with 2% dairy–yeast prebiotic, 5% fish meal, and 4% or 10% PF; and two 4% or 10% PF diets that contained no fish meal or prebiotic. To compare diet effects in the presence or absence of natural foods, one trial was conducted in indoor aquaria and one was conducted in outdoor pools. Diet effects were assessed by measuring growth, survival, feed efficiency, and body composition in both trials and Fulton's condition factor K in the outdoor pool trial. A subset of fish from the outdoor trial was grown to a larger size for analysis of alternative complement activity (ACH50). The prebiotic enhanced growth and feed conversion ratio (FCR) slightly in the indoor aquarium trial. Weight gain and FCR did not differ among diet groups in the outdoor trial, reflecting the influence of natural foods. Survival in aquaria was higher in fish fed the 10% PF diets than in fish given the 4% PF diets. The prebiotic slightly reduced survival in outdoor pools, but survival was 96% or higher for all diet groups. The K‐value was higher in fish that were given 10% PF diets than in fish fed 4% PF diets. Whole‐body proximate composition was similar among treatment groups for the aquarium trial. In the outdoor trial, whole‐body lipid was higher in fish fed the diets with 10% PF versus those fed diets with 4% PF, and dry matter followed a similar pattern. The ACH50 was similar between golden shiners that were fed diets with the prebiotic and those given diets without the prebiotic. Fish meal did not enhance any of the performance criteria in golden shiners held in tanks or pools. Although prebiotic addition and lipid concentration significantly affected several aspects of fish performance and body composition, some of the differences were numerically small. Economic analysis should be conducted to determine whether addition of a prebiotic or extra lipid to commercial diets is justified for production and distribution of golden shiners.

Swimming Performance and Metabolism of Cultured Golden Shiners

AbstractSwimming performance and metabolism of golden shiners Notemigonus crysoleucas were examined by use of swim tunnel respirometry. The oxygen consumption and tail beat frequency (TBF) at various swimming speeds, an estimation of the standard metabolic rate (SMR), and the critical swimming speed (U crit) were determined for golden shiners that were tested in 10 groups of 5 individuals each. Oxygen consumption and TBF both increased as swimming speed increased. The mean U crit for the first, second, and third individual to fatigue in each group was 38.0, 41.7, and 47.2 cm/s, respectively. The SMR was estimated at 131 mg O2·kg−1·h−1 for fish averaging 5.3 g. The active metabolic rate averaged 150 ± 14 mg O2·kg−1·h−1 (mean ± SE) at 10 cm/s, increased to 163 ± 20 mg O2·kg−1·h−1 at 30 cm/s, and peaked at 177 ± 19 mg O2·kg−1·h−1 at 50 cm/s. Total aerobic cost of transport (0.36 cal·g−1·km−1; i.e., the metabolic cost of swimming) and net cost of transport (0.08 cal·g−1·km−1) were lowest between 30 and 40 cm/s.

Effects of Temperature on the Growth of Golden Shiners in Aquaria

AbstractControl of fish size is critical to baitfish production and marketing, and temperature is a major factor affecting fish growth. Temperature‐dependent growth models were developed for juvenile golden shiners Notemigonus crysoleucas. Two 10‐week trials with two juvenile sizes (0.5 and 1.0 g) were conducted in a flow‐through aquarium system to determine the growth response to temperature. Four temperature treatments (15, 20, 25, and 30°C) were randomly assigned to twenty 110‐L glass aquaria; 20 fish were stocked into each aquarium. Each aquarium received a constant inflow of water at a rate of approximately 200 mL/min, equivalent to a total water exchange every 9 h. Fish were hand fed twice daily to apparent satiation with a commercial minnow feed (32% crude protein) that had been crumbled and sieved (particle size < 0.85 mm). Fish in each aquarium were batch weighed and counted every 2 weeks to document growth and survival. Average survival across treatments ranged from 93% to 96% for 0.5‐g fish and from 91% to 97% for 1.0‐g fish, and survival was not significantly different among treatments (P > 0.05). Quadratic equations were derived to predict maximum rates of total weight growth (ΔW, g/d) and total length growth (ΔL, mm/d) from temperature. Under study conditions, ΔW was obtained at 26.0°C for 0.5‐g fish and at 24.1°C for 1.0‐g fish; ΔL was obtained at 26.0°C for 0.5‐g fish and at 23.9°C for 1.0‐g fish. Documenting the relationship of temperature to growth could lead to improvements in baitfish farming techniques. A combination of pond and tank culture would make it possible to extend the growing season or to stockpile quantities of different sizes of fish to meet market requirements.

Diet Composition and Overlap in a Mixed Warm- and Coldwater Fish Community

ABSTRACT In Twin Lakes, Washington, illegal introductions of largemouth bass (Micropterus salmoides) and golden shiner (Notemigonus crysoleucas) are feared to be impacting economically important rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis) populations. We evaluated the stomach contents of 69 golden shiner, 146 rainbow trout, 83 brook trout, and 561 largemouth bass during summer stratification in 2004 and 2005, to determine community diet composition and overlap when food resources were partitioned thermally and spatially. Gut content data revealed some diet overlap but also illustrated distinct resource partitioning among all species but not between salmonids. Rainbow and brook trout had similar pelagic based diets of zooplankton and chaoborids, with high estimated diet overlap. Largemouth bass ≥300 mm was piscivorous and consumed principally golden shiner, with some consumption of rainbow and brook trout during late spring and early fall. Largemouth bass ≤299 mm primarily consumed benthic invertebrates in littoral macrophyte beds. Golden shiner diet contained both littoral and pelagic items, consisting of algae, benthic invertebrates, and zooplankton. Preferential differences in temperature, dissolved oxygen, and habitat as well as species size and ontogeny may all contribute to resource partitioning in the Twin Lakes.

Preliminary Observations of Mortality Reduction in Stressed, Flavobacterium columnare–Challenged Golden Shiners after Treatment with a Dairy‐Yeast Prebiotic

AbstractWe conducted preliminary studies to evaluate the effects of including dairy‐yeast prebiotics in the diets of golden shiners Notemigonus crysoleucas with access to natural foods on their resistance to challenge with Flavobacterium columnare. In trial 1, fish were fed either a control diet or a 2% dairy‐yeast prebiotic diet for 10 weeks in outdoor pools before challenge. In trial 2, fish fed the experimental diets were either subjected to confinement stress or left unmolested before challenge. Mortality (mean ± SE) was not significantly different in the control diet (23.4 ± 3.4%), the prebiotic diet (10.0 ± 3.3%), and the prebiotic diet with stress (16.7 ± 3.4%) treatments. However, mortality was significantly greater in the control diet with stress treatment (50.0 ± 3.3%) than in the other treatments. This preliminary investigation suggests that prebiotic supplementation in golden shiner feeds before a stressful event would significantly reduce the mortality from F. columnare.

Complete characterisation of the American grass carp reovirus genome (genus Aquareovirus: family Reoviridae) reveals an evolutionary link between aquareoviruses and coltiviruses

An aquareovirus was isolated from several fish species in the USA (including healthy golden shiners) that is not closely related to members of species Aquareovirus A, B and C. The virus, which is atypical (does not cause syncytia in cell cultures at neutral pH), was implicated in a winter die-off of grass carp fingerlings and has therefore been called ‘American grass carp reovirus’ (AGCRV). Complete nucleotide sequence analysis of the AGCRV genome and comparisons to the other aquareoviruses showed that it is closely related to golden ide reovirus (GIRV) (> 92% amino acid [aa] identity in VP5(NTPase) and VP2(Pol)). However, comparisons with grass carp reovirus ( Aquareovirus C) and chum salmon reovirus ( Aquareovirus A) showed only 22% to 76% aa identity in different viral proteins. These findings have formed the basis for the recognition of AGCRV and GIRV as members of a new Aquareovirus species ‘ Aquareovirus G’ by ICTV. Further sequence comparisons to other members of the family Reoviridae suggest that there has been an ‘evolutionary jump,’ involving a change in the number of genome segments, between the aquareoviruses (11 segments) and coltiviruses (12 segments). Segment 7 of AGRCV encodes two proteins, from two distinct ORFs, which are homologues of two Coltivirus proteins encoded by genome segments 9 and 12. A similar model has previously been reported for the rotaviruses and seadornaviruses.

Growth, condition, diet, and consumption rates of northern pike in three Arizona reservoirs

Northern pike (Esox lucius L.) introductions are controversial in the western United States due to suspected impacts they might have on established sport fisheries and potential illegal introductions. Three Arizona reservoirs, Parker Canyon Lake, Upper Lake Mary and Long Lake were sampled to examine the diet, consumption dynamics, and growth of northern pike. Northern pike diets varied by season and reservoir. In Parker Canyon Lake, diets were dominated by rainbow trout in winter and spring and bluegill and green sunfish in the fall. In Long Lake the northern pike ate crayfish in spring and early summer and switched to young of the year common carp in summer and fall. Black crappie, golden shiners, and crayfish were the major prey in Upper Lake Mary during spring, but they switched to stocked rainbow trout in the fall. Northern pike growth was in the high range of growth reported throughout the United States. Estimated northern pike specific consumption rate (scr) of rainbow trout (g/g/d × 10−6) was greatest in Upper Lake Mary (scr = 329.1 ± 23.7 g/g/d × 10−6) where stocked fingerling (<120 mm total length [TL]) rainbow trout were most vulnerable to these predators, compared to larger (>280 mm TL) rainbow trout stocked in Long Lake (scr = 1.4 ± 0.1 g/g/d × 10−6) and Parker Canyon Lake (scr = 287.2 ± 15.1 g/g/d × 10−6) where catchable-sized rainbow trout were stocked. Managers should consider the cost-benefits of stocking fish >200 mm TL in lakes containing northern pike.

PHYLOGENETIC AFFINITIES OF PLAGIOCIRRUS VAN CLEAVE AND MUELLER, 1932 WITH THE DESCRIPTION OF A NEW SPECIES FROM THE PASCAGOULA RIVER, MISSISSIPPI

Plagiocirrus loboides n. sp. (Digenea: Opecoelidae) is described from Fundulus nottii, F. dispar blairae, F. chrysotus, and Notemigonus crysoleucas from the Pascagoula River in Mississippi. Plagiocirrus loboides differs from P. primus Van Cleave and Mueller, 1932, by having a longer postcecal space (14-25% of body length vs. about 7%); a more anterior vitellarium (extending at least to the middle of the ventral sucker vs. to its posterior margin); and larger eggs (51-71 microm long by 23-34 microm wide vs. 40-55 microm long by 30-35 microm wide). Plagiocirrus loboides differs from P. testeus Fritts, 1959, by having a long postcecal space (vs. < 5% of body length); irregular, oblique, contiguous testes (vs. strongly lobed, well separated, tandem testes); and a more extensive vitellarium. Plagiocirrus loboides differs from both congeners by having an ovary comprised of 3 or 4 distinct lobes rather than having an entire ovary. Plagiocirrus wuyienensis Wang, 1981, from Hemimyzon zebroidus in Fujian Province, China, is herein considered a species inquirenda because it has a Y-shaped excretory bladder. Molecular phylogenetic analysis of 28S rDNA gene fragments from P. loboides and 17 digenean species demonstrates that Plagiocirrus belongs in Opecoelidae.

Mortality Rates in Golden Shiners Fed High‐Fat Diets with or without a Dairy‐Yeast Prebiotic before Challenge with Flavobacterium columnare

AbstractColumnaris, caused by Flavobacterium columnare, is a major bacterial disease of the golden shiner Notemigonus crysoleucas, especially when fish become stressed during handling and transport. Feed additives, such as a dairy‐yeast prebiotic, can decrease disease susceptibility in some fish species. Previous studies have indicated that diets with higher fat concentrations have improved the growth and survival of golden shiners. We conducted a study to determine whether a high‐fat diet alone or supplemented with a dairy‐yeast prebiotic could decrease mortality rates of golden shiners subjected to columnaris challenge. Golden shiners were assigned one of three diets with four replicate aquaria per diet and fed to apparent satiation twice daily for 16 weeks before the challenge. Diets (30.3 ± 0.31% crude protein; mean ± SE) were similar to a commercial formula and contained (1) 4% poultry fat (control), (2) 10% poultry fat, or (3) 10% poultry fat and 2% dairy‐yeast prebiotic. After the 16‐week feeding period, 15 golden shiners (2.2 ± 0.03 g) from each aquarium were stocked into different aquaria (experimental replicates were maintained) and exposed to 20 mL of columnaris bacteria in Sheih broth (optical density, 0.395 Å; at 560 nm; Sheih broth blank) for 18 h. Kidney cultures taken from moribund fish were streaked on Sheih agar to confirm the presence of columnaris and an active infection. Mortality in the 4% poultry fat (41.7 ± 12.9%) and 10% poultry fat (40.0 ± 6.1%) diets was high and not significantly different. Mortality for the dairy‐yeast prebiotic (6.7 ± 2.7%) diet was much lower and significantly different from that for the 4% and 10% poultry fat diets. Thus, the dairy‐yeast prebiotic effectively reduced mortality rates in golden shiners exposed to columnaris, but a high‐fat diet alone provided no protection relative to the lower‐lipid control diet.

Insulin Response of Largemouth Bass to Glucose, Amino Acid, and Diet Stimulation

AbstractInvestigation of the dietary requirements of largemouth bass Micropterus salmoides has intensified because of the popularity of this species. To determine commercial diets containing carbohydrate concentrations that are not detrimental to the health and survival of largemouth bass, we examined the effects of carbohydrate loads on insulin response. This study was intended to characterize the insulin response of largemouth bass to diet, glucose, and amino acids. Pellet‐trained largemouth bass were either orally stimulated with glucose, lysine, arginine, or methionine or fed a commercial pelleted diet or a “natural” diet of golden shiners Notemigonus crysoleucas, then bled over time to ascertain their insulin response. Insulin response was correlated with glucose response, the insulin responses lagging slightly behind increases in blood glucose concentration. Greater increases in blood glucose were accompanied by sharper, quicker insulin responses. Glucose (4.8 ± 0.3 ng insulin/mL) and arginine (5.4 ± 0.4 ng/mL) stimulation evoked the greatest mean insulin responses at 60 min postadministration; lysine (2.1 ± 0.3 ng/mL) also produced elevated insulin responses. The pelleted diet stimulated an intermediate response, whereas the diet of golden shiners produced the lowest insulin response. This study was intended to determine how the carbohydrate content of diets and subsequent influences on insulin response affect the health of largemouth bass. Because of confounding effects and interference from arginine and lysine in the diet, insulin response is not suitable for determining appropriate carbohydrate loads in largemouth bass diets. At this time, histological data and liver glycogen concentration should be used to determine appropriate carbohydrate loads in commercial diets.

3H] Citalopram Binding to Serotonin Transporter Sites in Minnow Brains

Mammalian serotonin (SERT) and norepinephrine transporters (NET) are target sites for antidepressants and are affected by pesticide exposures. Herein, we examined whether golden shiner (Notemigonus crysoleucas) or fathead minnow (Pimphales promelas) SERTs and catecholamine transporters respond comparably to mammalian SERTs and NETs. We compared the pharmacological profiles of central SERT and NET binding sites of the golden shiner minnow to those of rats. Homogenate binding with the radioligand [(3)H] citalopram indicated that golden shiner SERT has a K(D) of 7 +/- 3 nM and a B(max) of 226 +/- 46 fmol/mg protein. These values are similar to those of rat cortical SERT (K(D) 1.4 +/- 0.1 nM and B(max) 240 +/- 48 fmol/mg protein). We also examined SERT binding in fathead minnow brain, and found it similar to that of the golden shiner. A putative golden shiner NET, measured using [(3)H] nisoxetine, had K(D) = 12 +/- 5 nM and B(max) = 187 +/- 49 fmol/mg protein, whereas rat hippocampal NET had K(D) = 5 +/- 2 nM and B(max) = 93 +/- 8 fmol/mg protein. Minnow SERT and NET binding is displaceable by selective reuptake inhibitors. Finally, we exposed zebrafish (Danio rerio) to the serotonin reuptake inhibiting antidepressant sertraline or the organophosphate chlorpyrifos for 21 days. After either treatment, SERT binding was reduced by 50% (n = 3-6, P < 0.05). In summary, minnow central SERT and NET express slightly lower affinity for antidepressants than rats. However, magnitudes of affinity are similar, and minnow SERT binding is decreased by chronic sertraline or chlorpyrifos administration.

Validation, use, and disadvantages of enzyme-linked immunosorbent assay kits for detection of cortisol in channel catfish, largemouth bass, red pacu, and golden shiners

Measurement of cortisol response is an important tool to asses stress in fisheries research. Radioimmunoassay (RIA) is a common method for the measure of cortisol in fish. Use of enzyme-linked immunosorbent assays (ELISA) to detect cortisol would eliminate health hazards, costs of handling radioisotopes, and the short stability time associated with RIA. Enzyme-linked immunosorbent assays have been used for the determination of cortisol in several fish species. However, the ELISA method of cortisol determination in fish lacks proper validation testing. We conducted validation procedures for multiple commercial cortisol ELISA kits and compared the results to RIA. The assays were tested for four species: (1) channel catfish Ictalurus punctatus, (2) largemouth bass Micropterus salmoides, (3) red pacu Piaractus brachypomus, and (4) golden shiners Notemigonus crysoleucas. We evaluated the ELISA methods against RIA, and determined that at least one kit is suitable (accuracy: mean recovery of spiked samples, 102.8%; reproducibility: interassay coefficient of variation < 10.5% for all species; precision: intra-assay coefficient of variation < 16.8% for all species; linearity: R (2) > 0.96 for all species) for the measurement of cortisol response in fish and comparative determination of stress. All of the ELISA assay results varied by more than 10% from the cortisol concentrations detected by the RIA. The high variability of the kit results indicates that commercial ELISA kits could be utilized for qualitative determination of cortisol in fish, but should be fully validated in each laboratory for each species before being used for research.

Validation of a quantitative PCR diagnostic method for detection of the microsporidian Ovipleistophora ovariae in the cyprinid fish Notemigonus crysoleucas

Microsporidian parasites are easily detected by light microscopy when infections are heavy and spores are present. However, early infections without spores, or light infections with low numbers of spores, are easily missed. This limitation has made it difficult to conduct investigations into microsporidian prevalence and transmission. In this study, we developed a quantitative TaqMan polymerase chain reaction assay to assess the presence of Ovipleistophora ovariae in the tissues of the cyprinid fish Notemigonus crysoleucas (golden shiner). The efficiency of the primer set was 100.8%, with a correlation coefficient of threshold position to copy number of 0.997 over 9 logs using a plasmid containing the cloned reaction product. No product was produced from other closely related microsporidian species (Nucleospora salmonis, Pseudoloma neurophila, Glugea stephani, Heterosporis sp., and O. mirandella). The coefficient of variation for replicate assays done on different days was 12.4%. The assay detects O. ovariae reliably at less than 10 genomic copies and 0.14 spores per reaction, but maximum sensitivity is only achieved when sonication is included as part of the DNA purification step. Using the assay, we found 4.44 x 10(1) to 7.91 x 10(6) copies microg(-1) host DNA in female golden shiners, with the spore density increasing during the spawning season. The parasite was also detected for the first time in the testes of male golden shiners at 2.60 x 10(1) to 8.62 x 102 copies microg(-1) host DNA.

The Acute Toxicity of Praziquantel to Grass Carp and Golden Shiners

AbstractThe acute toxicity and highest nonlethal concentration of praziquantel (LC0) were determined in the laboratory for grass carp Ctenopharyngodon idella and golden shiner Notemigonus crysoleucas, two cyprinids known to harbor the Asian tapeworm Bothriocephalus acheilognathi. Praziquantel is an anthelmintic used to treat fish with tapeworms. The 24‐h and 96‐h LC50 values were 55.1 and 49.7 mg/L for golden shiners (1.3 g) and 63.4 and 60.6 mg/L for grass carp (9.1 g). The 24‐h and 96‐h LC0 values were 50.0 and 45.0 mg/L for golden shiners and 60.0 and 60.0 mg/L for grass carp.

Foraging Behavior and Monetary Impact of Wading Birds at Arkansas Baitfish Farms

— We conducted foraging observations, food habits studies, and producer surveys to determine the foraging behavior and monetary impact of great blue herons Ardea herodas, great egrets A. alba, and little blue herons Egrerra caerulea foraging at Arkansas baiffish farms. Although great egrets captured most baitfish/minute, captures/strike were nearly identical among the three wading bird species. American gizzard shad Dorosoma cepedianum, goldfish Carassius auratus, and giant water bugs Hemiptera: Belostomatidae were collected from the gastro-intestinal tract of great blue herons. Only golden shiners Noremgonus crysoleucas and goldfish were found in great egrets. We found dragonflies Odonata, golden shiners, green sunfish Lepomis cyanellus, and water bugs in little blue herons. In contrast to other birds collected, snowy egrets E. thula were found to contain mosquito fish Gambusia affinis. Among 2,742 teleost otoliths recovered from collected great blue herons, great egrets, and little blue herons, most otoliths belonged to the Cyprinidae family (including the baiffishes). Surveyed farm managers use various auditory and visual stimuli to disperse fish-eating birds from their farms. Surveyed baitfish farmers suggested that the average cost of their annual bird harassment program was $11,580 at relatively small farms (< 202 ha) and $104,560 at relatively large × 202 ha) baitfish aquaculture facilities. We estimated the replacement cost of baitfish consumed by wading buds based upon their daily food requirements, the food habits of herons and egrets at baiffish farms, the hypothetical abundance of wading birds at a particular baitfish farm (relative to survey results), the duration of herons and egrets reported by farm managers, and current baitfish market values.

Volume and Lipid, Fatty Acid, and Amino Acid Composition of Golden Shiner Eggs during a Spawning Season

AbstractThe Arkansas baitfish industry leads the nation in production of golden shiners Notemigonus crysoleucas. To determine nutritional requirements for golden shiner broodstock diets, we examined the volume and lipid, fatty acid, and amino acid composition of the eggs produced by a group of captive broodstock over a spawning season. Egg volume was 0.67 ± 0.117 mm3 (mean ± SD); egg volume declined during the spawning season. Total lipid was 15.67 ± 2.99 μg/egg, and triacylglyceride (TAG) concentration was 6.82 ± 1.81 μg/egg. Based on the stability of egg total lipid, the percent neutral lipid, the consistent contribution of TAG to neutral lipid, the consistent TAG concentration, and the stable fatty acid and amino acid profiles, we conclude that the lipid and amino acids in eggs from the experimental group were stable. The eggs should be equally sufficient for embryological development throughout the spawning season, but specific indices of egg and fry quality must be measured to confirm the links among egg size, biochemical composition, and egg and fry quality.

Differential Prey Selectivity of Largemouth Bass Functional Feeding Groups in Twin Lakes, Washington

Largemouth bass (Micropterus salmoides) can be top-down regulators in a fish community. It is important for fisheries biologists who manage predator-prey populations to understand when bass become piscivorous. We examined the stomach contents of 622 largemouth bass in watershield (Brasenia schreberi) beds in North and South Twin Lakes, Washington. Bass displayed temporal and ontogenetic diet variation within and between lakes. Bass <100 mm fed principally on zooplankton and scuds in June and September and on benthic invertebrates, especially midge and damselfly larvae, during July and August. Damselflies, midges and scuds were major diet constituents for bass 100–199 mm. Bass 200–299 mm consumed large numbers of macroinvertebrates but also fed on crawfish and golden shiner (Notemigonus crysoleucus). Overall, the importance of large prey items like golden shiners and crawfish increased while macroinvertebrate importance to bass diets decreased as the fish grew larger. Bass piscivory was focused on golden shiners and was only observed in larger fish >300 mm. Golden shiner consumption was the lowest during June and September when cannibalism, crawfish and trout consumption increased. Temporal and ontogenetic variability in bass diets is most likely due to habitat variability, fish size, and prey availability and size. Manipulation of bass piscivory through slot-length-limits and/or macrophyte removal could be examined as a potential method for controlling nuisance forage fish such as golden shiners.