Control of the Trematode Bolbophorus confusus in Channel Catfish Ictalurus punctatus Ponds Using Salinity Manipulation and Polyculture with Black Carp Mylopharyngodon piceus

This study evaluated the use of black carp Mylopharyngodon piceus and salinity manipulation for controlling the infection of channel catfish Ictalurus puncratus by a digenetic trematode (tentatively identified as Bolbophorus confusus ). Control methods focussed mainly on the eradication of the intermediate snail host, the marsh rams-horn Phanorbella trivolvis (previously referred to as Helisoma trivolvis ), and were evaluated in laboratory tests and field experiments at a commercial catfish culture facility in southern Louisiana that was seriously impacted by the trematode. Introduction of fingerling black carp into catfish ponds at a density of 62 carpha resulted in an almost total elimination of P. trivolvis . The farm is now successfully using a facility-wide stocking rate of 40 carp/ha. Laboratory experiments were conducted to investigate the effect of salinity manipulation using NaCl on free-swimming trematode cercariae, the snail P. trivolvis , and catfish fingerlings infected with the cercariae. A salinity of 2.5 ppt had a detrimental effect on snail survival, growth, and reproduction. Salinity did not have a negative effect on the other two aspects of the trematode life cycle tested (in fact, survival of both cercariae and infected catfish fingerlings showed a positive dependence on NaCl over the 0–2.5 ppt range). A field-experiment was then conducted in catfish ponds maintained at three salinities (2.5, 1.25, and 0.25 ppt) with rock salt, NaCl. Snail densities in ponds at 2.5 ppt salinity were consistently lower than in the other treatments and no trematode infection was noted among snails or catfish in the 2.5 ppt salinity ponds. Both the use of 2.5 ppt NaCl and black carp appear valuable management tools for controlling the digenetic trematode in caffish ponds.     

Evaluating the potential effectiveness of harvest restrictions on riverine sunfish populations in Georgia, USA

Abstract  The effects of minimum length limits (MLLs) on bluegill, Lepomis macrochirus Rafinesque, redbreast sunfish, Lepomis auritus (Linnaeus), and redear sunfish, L. microlophus (Günther), fisheries in 13 river sections located across Georgia were evaluated. A Beverton–Holt equilibrium yield model was used to predict and compare the response of these fisheries to three MLL scenarios: 100 (i.e. no size limit), 125 and 150 mm. Model results indicated that natural mortality rates of all sunfish species examined in this study were low enough to allow harvest restrictions to be effective if growth was fast. If sunfish reached 203 mm in <4.0 years, then MLLs were generally effective in increasing size structure without decreasing yield or causing unacceptable declines in the number of fish available for anglers to harvest. Harvest restrictions resulted in minimal increases in size structure, declines in yield and a large decrease in the number of fish harvested by anglers if time to reach 203 mm was ≥ 8.0 years. Response to MLLs was more variable when fish grew to 203 mm in 4.0–6.5 years. Examination of mortality caps largely supported the results from the model, but there was indication that empirical rates of total annual mortality may have been biased high in some instances.     

Bioenergetic modelling of effects of fertilization, stocking density, and spawning on growth of the Nile tilapia, Oreochromis niloticus (L.)

Abstract. A bioenergetic growth model was developed to examine the integrated effects of fertilization, stocking density, and spawning on the growth of tilapia, Oreochromis niloticus (L.), in pond aquaculture. The analyses showed that growth rates increase with higher levels of organic fertilization up to 500kg/ha/week. Growth rates increased with added food rations in ponds, reaching a maximum growth of 2-07g/day at about 44–48 days after stocking. Fish growth rates decreased with increased levels of stocking density. The stocking density for optimal growth is 1fish/m²; the optimal density for total harvesting weight and fish size is 2 fish/m². Model sensitivity analysis indicated that tilapia growth is most sensitive to catabolism (metabolism) and anabolism (synthesis) coefficients, both of which are geometrically related to the fish body weight. Food assimilation efficiency (b) and the food consumption coefficient (h) have a modest effect on fish growth. Spawning in grow-out ponds can have a major effect on fish growth.     

Impact of Copper Sulfate on Plankton in Channel Catfish Nursery Ponds

Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04‐ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6–12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing.     

Feasibility of Pond Production of Largemouth Bass,Micropterus salmoides,for a Filet Market

The effects of stocking density on food‐size largemouth bass (LMB), Micropterus salmoides, production (>0.5 kg) were evaluated in a 2‐yr study by stocking LMB fingerlings (mean weight = 57 g/fish) in 0.1‐ha earthen ponds at rates of 6175, 12,350, or 18,525 fish/ha. Gross yields increased from 3989 to 9096 kg/ha as stocking density increased. No significant differences were observed in survival rates (range of 65–74%) due to density. Maximum feed consumption occurred at water temperatures of 27–30 C. Feed conversion ratio (FCR) and mean harvest weight were significantly different (P < 0.05) among densities, with the lowest FCR and the lowest mean weight found at the highest density (18,525 fish/ha). At harvest, LMB were considered to be in good condition with relative weight (W_r) values of 123–124. Dressout yield percentages were 61–62% for whole‐dressed LMB and 34–35% for shank filets. LMB grew well and reached a size adequate for targeted shank filet sizes. However, the production costs of $7.26–$9.34/kg mean that LMB production for a filet market is unlikely to be feasible. Research to lower LMB fingerling and feed costs and improved FCR would contribute to improved economic feasibility.     

Effects of stocking density on the growth rates of Cichlasoma urophthalmus (Günther) cultured in floating cages

Abstract. An experimental growth trial in floating cages at three different stocking densities was carried out. 15–19-cm mean total length, 18.5-g mean individual weight fish were stocked at 25, 50 and 1OO per m³. A 40% protein balanced diet was used as feed. The results of the study showed no statistically significant differences in growth among the three treatments. Food conversion ratios ranged from 3.10 to 3.34, and spiecific growth rates were between 1.40 and 1.48%/day.     

Production Characteristics of PanSize Channel Catfish in Cages and Open Ponds1

Production characteristics of pan-size (approximately 227 g) channel catfish (Ictalurus puncturus) were determined in cages and open ponds stocked with fingerlings to densities of 20,000 and 12,500 fish/ha. After 145 days, mean fish weight in all treatments exceeded 227 g. Mean survival was similar in all treatments. Food conversion ratios were significantly better in ponds than in cages but density did not affect the ratios. Neither density nor production system affected production (as measured by total weight produced) when initial density differences were considered (analysis of covariance). Variability in total length at harvest was similar between production systems; however, low density treatments were less variable than high density treatments. Results of this study indicate that pan-size channel catfish can be cultured efficiently at stocking densities well above the 12,500 fish/ha (5,000 fishlacre) generally used when culturing fish to larger sizes.     

Microbial changes occurring at the sediment-water interface in an intensively stocked and fed fish pond

The microbial changes occurring in the upper 1 cm of the solid sediment surface in intensively fed and aerated fish ponds located in northern Israel were examined. The bacterial groups enumerated included: total aerobes, total anaerobes, sulfate and iron reducing bacteria, ammonia and nitrite oxidizing bacteria, acid forming bacteria, and denitrifying bacteria. With the exception of the nitrifying bacteria, large microbial populations were observed in the pond sediment even prior to fish stocking. All the different groups enumerated displayed a rapid change in number during the first 2–8 days following fish stocking, and a subsequent approach toward a steady state. Since both microbial and chemical steady states were approached within a relatively short period of time, it does not appear that these components of the sediment are related to the inhibition of fish growth occurring 50–70 days after fish stocking. While the practice of pond draining and air drying the sediment does oxidize some of the accumulated organic material, it does not appear to affect the resident microbial flora significantly to an extent that could decrease the rate of reestablishment of the microbial community. Therefore, upon establishment of anaerobic conditions a large microbiological community is present capable of mediating the chemical reduction of SO₄^2? to H₂S, or other transformations resulting in products which contribute to fish growth inhibition commonly observed in such intensively stocked and fed fish ponds.     

The effect of stocking size on the first winter survival of whitefish, Coregonus lavaretus (L.), in the Gulf of Bothnia, Baltic Sea

The anadromous whitefish, Coregonus lavaretus (L.), is the most numerous fish species stocked in the Gulf of Bothnia, Baltic Sea. One-summer-old-whitefish fingerlings are mostly 8–10 cm long when released annually in September–October, whereas the wild whitefish are 10–12 cm at that time. About 6 million, one-summer-old, spray-marked, whitefish were released in the northern and central parts of the Gulf in 1995–1998. To study the effect of the stocking length on the survival of the marked fish, the length of the recaptured whitefish as 1-year-olds was back-calculated. Altogether 1106 whitefish recaptured in the Gulf of Bothnia were analysed. The back-calculated length was slightly greater than the stocking length but not as large as the length of the wild fish. In the central part of the Gulf of Bothnia, where the mean stocking length was more than 10 cm, the back-calculated length was 10.5–11.1 cm. In the northern part of the Gulf the mean stocking length varied between 8.8 and 10.0 cm annually, and the corresponding back-calculated mean lengths were 9.3–9.7 cm. It also seemed that bigger fingerlings started their feeding migration earlier or they migrated faster than the smaller ones to the southern parts of the Gulf of Bothnia.     

An Economic Analysis of the Performance of Three Sizes of Catfish Ictalurus punctatus Fingerlings Understocked in Multiple-Batch Production

Abstract.— Different sizes of catfish fingerlings understocked in multiple-batch production may result in different survival, yield, cost, and economic risk. A pond production study was conducted to compare net yield, growth, survival, costs, and economic risk of understocking 7.6-cm, 12.7-cm. or 17.8-cm channel catfish Ictalurus punctatus fingerlings in growout ponds. Fingerlings were understocked at 15,000/ha with 1,369 kg/ha carryover fish averaging 0.58 kg. Mean growth rate increased significantly with size of fingerling understocked (1.4 ± 0.2 g/d, 1.8 ± 0.07 g/ d, and 2.2 ± 0.06 g/d for 7.6-cm, 12.7-cm, and 17.8-cm understocked fingerlings, respectively). Mean individual weights at harvest also increased significantly with size at stocking but none of the understocked fingerlings reached minimum market size (0.57 kg) over the 201-d study period. Survival of the smallest (7.6-cm) understocked fingerlings was significantly lower, but there was no difference in survival between the two other treatments. Net yields were highest for the two treatments understocked with 12.7- and 17.8-cm catfish and significantly lower for the treatment understocked with 7.6-cm fish. Growth of large carryover fish was significantly less in the treatment understocked with 17.8-cm fingerlings. Breakeven production costs were highest for the treatment understocked with 7.6-cm fish and lower for the other two treatments. The risk analysis showed that it was very likely that the 12.7- and 17.8-cm understocked fish could be grown profitably (very little risk of costs exceeding $ 1.32/kg—$1.65/kg). However, the risk of growing out 7.6-cm understocked fish at costs above market prices increased sharply. This static analysis indicated that the preferred size to understock in growout ponds would be 12.7 cm; however, additional work is needed in a dynamic framework to quantify the benefit of 17.8-cm fingerlings reaching market size earlier in the second year.     

Strategies for Development of Rotifers as Larval Fish Food in Ponds

Strategies to sustain rotifer peak biomass, distribution of rotifer resting eggs in the sediment, and relationship between rotifers and larval fish growth were studied in a series of pond experiments. After the ponds were filled with water, herbivorous rotifers (e.g., Brachionus calyciflorus ) developed first, but were gradually replaced by predatory rotifers (e.g., Asplanchna ). Subsequently, herbivorous cladocerans (e.g., Moina sp) eventually replaced rotifers and dominated the zooplankton community. The occurrence of Asplanchna and Moina indicated the decline of B. calyciflorus . Peak rotifer biomass developed 8–10 d after the ponds were filled with water at 20–25 C, 10–15 d at 17–20 C, 15–20 d at 15–17 C, 20–30 d at 10–15 C, and >30 d at < 10 C. The abundance of resting eggs in the top 5-cm sediment varied from 6 to 83/cm². About 25% of resting eggs were buried in the top 5-cm sediment but the number of resting eggs decreased with increased sediment depth. Optimum rotifer biomass for silver carp Hypophthalmichthys molitrix larvae stocked at 1,500,000/ha was 20–40 m/gL. High rotifer biomass (>20 mg/L) usually lasted 3–5 d, but could be prolonged by pond fertilization or cladoceran controls. A weekly application of dipterex at 0.05 mg/L reduced cladoceran biomass but enhanced rotifer biomass. Our results indicate with a careful management plan it is possible to synchronize the rotifer development with larval fish stocking.     

Effect of Stocking Density on Growth and Water Quality for Largemouth Bass Micropterus salmoides Growout in Ponds

Juvenile largemouth bass Micropterus salmoides , trained to accept artificial diets, were stocked into six 0.04-ha ponds at stocking densities of either 6,175 or 12,350 fish/ha. Fish were fed a floating custom-formulated diet, containing 44% protein, once daily to satiation for 12 mo (May 1994–May 1995). At final harvest, the total yield of fish was significantly greater (P < 0.05) and feed conversion ratio (FCR) was significantly lower, for bass stocked at the higher density (4,598 kg/ha and 2.3, respectively) than when stocked at the lower density (2,354 kg/ha and 3.3, respectively). There was no significant difference (P > 0.05) in average weight, length, or survival of bass stocked at the two densities. Averaged over the study period, there were no significant differences (P > 0.05) in total ammonia-nitrogen (TAN), nitrite-nitrogen, or un-ionized ammonia concentrations in ponds in which bass were stocked at the two densities. These data indicate that largemouth bass of the size used in this study are amenable to pond culture at densities of at least 12,350 fish/ha and that higher stocking densities may be possible.     

Sanguinicola fontinalis sp nov. (Digenea: Sanguinicolidae): a blood parasite of brook trout, Salvelinus fontinalis (Mitchill), and longnose dace, Rhinichthys cataractae (Valenciennes)

Abstract. Sanguinicola fontinalis sp. nov., from the branchial, renal and cardiac blood vessels of brook trout. Salvelinus fontinalis (Mitchill), and longnose dace, Rhinichthys cataractae (Valenciennes), is described. The new species most closely resembles, hut differs from, Sanguinicola davisi of steelhead and rainbow trout, Salmo gairdneri Richardson. The adult differs from all known North American species in having 29–33 lateral tufts of blunt spines. The snail host is Leptoxis (Mudalia) carinata (Bruquière, 1792). Lodged and migrating miracidia caused considerable gill damage in the brook trout, resulting in high mortality when the fish were moved. To remove the hazard, the most severely affected brook trout were destroyed and the ponds drained and disinfected. Adult worms from Pennsylvania brook trout and West Virginia longnose dace were studied, as well as infected snails.     

Evaluation of a trawl to estimate the inventory of catfish in commercial ponds

Most commercial catfish farms use multiple-batch production systems that contain fish sizes ranging from recently stocked fingerlings to fish weighing more than 1.5 kg. Currently, there are no accurate and cost-effective techniques to estimate pond inventories of catfish. Three trials were conducted in earthen catfish ponds with a 12 m × 8 m trawl (bar mesh at mouth of 3.8-cm; 2.54-cm at cod end). The first two trials included trawling with and without feed as bait in 4-ha commercial catfish ponds (Trial 1) and in 1.6-ha experimental ponds (Trial 2). In Trial 3, the trawl was pulled three times without feeding in 1.6-ha experimental ponds. Mean individual weights and size distributions of catfish caught by the trawl were statistically similar to those of catfish caught by the seine (Trial 1) and to stocking data (Trial 2). Single pulls with the trawl resulted in 73% error in estimated fish inventories in Trial 3. However, if pulled two times, the estimated catfish inventory error dropped to 7%, more accurate than other inventory methods, but was variable (coefficient of variation = 186%). The trawl appears to have potential as a means to sample commercial catfish ponds to estimate means and frequency distributions of fish size, but additional refinement and correction would be needed for it to be used reliably to estimate total pond inventory.     

Pond Culture of Larval and Juvenile Cobia,Rachycentron canadum,in the Southeastern United States

Abstract

The potential of growing larval and juvenile cobia, Rach-ycentron canadum, in ponds was investigated. Larval cobia, obtained from tank spawning of wild-caught adults, were stocked 48-72-h post-hatch at a rate of 700,000/ha into three fertilized 0.25-ha ponds. At one week post-stocking (WPS), fish were observed consuming formulated feed. Growth was rapid, with specific growth rates (SGR) ranging from 12.5-19.2% body weight/day. At harvest (5 WPS) fish reared in two ponds weighed 7.9 and 9.3 g and total length (TL) was 118.9 and 129.3 mm, respectively (all fish reared in remaining pond died the night prior to harvest due to aerator failure). Feed conversion ratio (FCR) was 3.8 for both ponds and survival was 5.3 and 8.5%. Low survival rates were thought to be due primarily to cannibalism. Immediately after harvest, fish were restocked into two 0.25-ha ponds at a stocking rate of 14,400/ ha. Fish were fed formulated, pelleted feeds. Growth was rapid up to ～9 WPS, after which pond water temperatures declined. Ponds were harvested at 13 and 15 WPS, respectively. Final weight of fish was 309.9 and 362.5 g. Final TL was 343.1 and 355.7 mm. FCR was 3.8 and 4.5 and survival was 27.5 and 30.5%. Major losses of fish were associated with avian predators and possibly a toxic algal bloom. Results of trials indicate that cobia larvae and juveniles can be reared in pond-based culture systems, however additional research is needed to refine this approach.     

Appropriate Timing of Supplemental Feeding for Production of Nile Tilapia, Silver Carp, and Common Carp in Fertilized Polyculture Ponds

In an attempt to identify appropriate times for initial application of supplemental feed in polyculture fertilized fish production earthen ponds, a study was conducted for 19 wk to establish the growth performance, yield, survival, and body composition of Nile tilapia, common carp, and silver carp as influenced by four different feeding regimens (treatments). The four treatments were: 1) supplemental feeding beginning at onset of the experiment (T-I) (control treatment); 2) 6-wk delay of feeding after fish stocking (T-II); 3) 13-wk delay of feeding after fish stocking (T-III), and 4) no supplemental feed application (T-IV). Two ponds were assigned to each treatment and each pond was stocked with a similar number and weight of each fish species. A commercial pelleted fish feed (25% protein) was used to feed fish in T-I, T-II, and T-III at 3% of their body weight, twice a day. At the end of the experiment, fish species (except for silver carp) in T-II showed weight gain, growth rates, and yields significantly higher than fish in T-III or T-IV. Also, the total fish production and net profit in T-II were significantly higher than in T-III or T-IV. Fish species in T-II showed weight gain, growth rates, survival rates, and yields similar to those of T-I (control treatment) with no significant differences. The amount of feed consumed by fish in T-II was reduced by approximately 7.3% compared to that consumed by fish at T-I. Moreover, there was increase in th net profit in T-II by 4.8% over that achieved in T-I. Therefore, T-II appears to be the most appropriate among the tested feeding treatments and recommended for use in order to achieve the best growth, production, and net profit.     

Quantifying risks of volitional consumption of New Zealand Mudsnails by Steelhead and Rainbow Trout

To assess the risk of transferring alien, invasive New Zealand mudsnails (NZMS) Potamopyrgus antipodarum with shipments of live rainbow or steelhead trout Oncorhynchus mykiss, we conducted laboratory trials to quantify and determine the volitional ingestion of snails from the bottom of laboratory tanks. Approximately, 2000 snails were placed on the bottom of a test tank and groups of 10 fish were added to each tank. After 48 h, the fish were removed, euthanized and the snails in the gastrointestinal tract were counted, and the proportion of snails remaining in each tank was measured. We found that both rainbow trout and steelhead consumed NZMS, but rainbow trout consumed nearly twice the number of snails that were consumed by steelhead trout. Feeding fish a maintenance diet increased the total consumption of snails by fish to an average of 64.5 snails per rainbow trout. Our study suggests that management strategies that depurate fish without feed for 48 h to reduce the risk of transfer of NZMS are not viable in preventing the transport of snails if rearing waters contain snails.     

Impacts of Bolbophorus damnificus (Digenea: Bolbophoridae) on Production Characteristics of Channel Catfish,Ictalurus punctatus,Raised in Experimental Ponds

Bolbophorus damnificus was recognized as a threat to channel catfish, Ictalurus punctatus, production in Louisiana and Mississippi in 1997 and 1999, respectively. Severe to moderate outbreaks (≥34% prevalence) are correlated to heavy losses, but impact of mild outbreaks with low prevalence (<33%) was unknown. Laboratory and field studies were conducted to evaluate sublethal acute (early stage) and chronic (late stage) trematode infection impacts on catfish production. Fish raised in ponds seeded with ram's horn snails from ponds harboring active B. damnificus outbreaks resulted in infection prevalence ranging from 1.6 to 20.4%. Compared to fish raised in ponds not seeded with infected snails (0% prevalence), fish biomass, number harvested, and total feed fed were significantly lower. These data agree with previous studies where mild infections reduced feed consumption, fish production, and economic returns. Infected fish were collected from ponds and used in a laboratory growth study. Once removed from the infection source, weight gain, growth rate, feed consumption, and feed efficiency were equal to or greater than trematode‐free fish. This suggests that although early B. damnificus infection (premetacercarial development) can severely impact production, infection has little impact on performance once metacercarial cysts are fully developed, and the infection source is removed.     

Effect of Multiple-batch Channel Catfish, Ictalurus punctatus, Stocking Density and Feeding Rate on Water Quality, Production Characteristics, and Costs

To quantitatively define relationships among stocking densities, feeding rates, water quality, and production costs for channel catfish, Ictalurus punctatus, grown in multiple‐batch systems, twelve 0.1‐ha earthen ponds were stocked at 8,600, 17,300, 26,000, or 34,600 fingerlings/ha along with 2,268 kg/ha of carryover fish. Fish in all ponds were fed daily to apparent satiation using 32% protein floating feed. Temperature and dissolved oxygen in each pond were monitored twice daily; pH weekly; nitrite‐N, total ammonia nitrogen, and Secchi disk visibility every 2 wk; nitrate‐N, chlorophyll a, total nitrogen, total phosphorus, and chemical oxygen demand monthly; and chloride every other month. The costs of producing channel catfish at different stocking densities were estimated. There were no significant differences (P > 0.05) as a result of stocking density among treatment means of (1) gross or net yields, (2) mean weights at harvest, and (3) growth or survival of fingerlings (24–36%) and carryover fish (77–94%). Mean and maximum daily feeding rates ranged from 40 to 53 kg/ha/d and 123 to 188 kg/ha/d, respectively, and feed conversion ratios averaged 1.75. There were no differences in any feed‐related parameter as a result of density. Water quality variables showed few differences among densities at samplings and no differences when averaged across the production season. Yield of fingerlings increased as stocking density increased with significant differences between the two highest and the two lowest stocking densities. Breakeven prices were lower at the higher stocking densities as a result of the higher yield of understocked fish and similar mean individual fish weights produced at these higher stocking densities. Overall, varying stocking densities of fingerlings in multiple‐batch systems had little effect on production efficiency and water quality. Additional research on managing the population structure of carryover fish in commercial catfish ponds may be warranted.     

Effects of littoral habitat complexity and sunfish composition on fish production

Carey MP, Maloney KO, Chipps SR, Wahl DH. Effects of littoral habitat complexity and sunfish composition on fish production. Ecology of Freshwater Fish 2010: 19: 466–476. © 2010 John Wiley & Sons A/S Abstract – Habitat complexity is a key driver of food web dynamics because physical structure dictates resource availability to a community. Changes in fish diversity can also alter trophic interactions and energy pathways in food webs. Few studies have examined the direct, indirect, and interactive effects of biodiversity and habitat complexity on fish production. We explored the effects of habitat complexity (simulated vegetation), sunfish diversity (intra‐ vs. inter‐specific sunfish), and their interaction using a mesocosm experiment. Total fish production was examined across two levels of habitat complexity (low: 161 strands m^?2 and high: 714 strands m^?2) and two sunfish diversity treatments: bluegill only (Lepomis macrochirus) and bluegill, redear sunfish (Lepomis microlophus), and green sunfish (Lepomis cyanellus) combination. We also measured changes in total phosphorus, phytoplankton, periphyton, and invertebrates to explain patterns in fish production. Bluegill and total fish production were unaffected by the sunfish treatments. Habitat complexity had a large influence on food web structure by shifting primary productivity from pelagic to a more littoral pathway in the high habitat treatments. Periphyton was higher with dense vegetation, leading to reductions in total phosphorus, phytoplankton, cladoceran abundance and fish biomass. In tanks with low vegetation, bluegill exhibited increased growth. Habitat complexity can alter energy flow through food webs ultimately influencing higher trophic levels. The lack of an effect of sunfish diversity on fish production does not imply that conserving biodiversity is unimportant; rather, we suggest that understanding the context in which biodiversity is important to food web dynamics is critical to conservation planning.