Developing sustainable aquaculture methods for the mummichog, Fundulus heteroclitus, with emphasis on egg production

Final Report for GNE11-023

Project Type: Graduate Student
Funds awarded in 2011: $14,909.00
Projected End Date: 12/31/2012
Grant Recipient: Delaware State University
Region: Northeast
State: Delaware
Graduate Student:
Faculty Advisor:
Dennis McIntosh, Ph.D.
Delaware State University
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Project Information

Summary:

Mummichogs, Fundulus heteroclitus, are a popular marine baitfish along eastern North America. Due to seasonal availability in size and quantity, as well as increasing wholesale prices, there has been an increased interest in growing these fish on a commercial scale. Farming these fish could reduce environmental impacts on salt marsh ecosystems and improve the economic stability of the marine baitfish industry. However, concern for low production numbers and lack of species-specific research has hindered expansion of mummichogs as a farmed species. This research explores species-specific egg production techniques while simultaneously examining alternative labor regimes for the most efficient labor-to-yield ratio. To test this, egg collectors were placed at different depths (8, 16, or 24 cm) below the surface of the water in tanks of spawning mummichogs to determine if depth would affect egg production in the absence of tides. Eggs were collected either two or three times per week to evaluate whether removing eggs from tanks more frequently would increase egg health and thus fry yield, and if this collection frequency affected anticipated labor costs. After eight weeks it was clear that significantly more eggs were deposited in the shallowest collectors for the triweekly collection which was not significantly different from biweekly collections at any depth. Fry yield was not increased with more frequent collections. For mummichog egg production we recommend retrieving eggs biweekly for the most efficient yield-to-labor ratio.

Introduction:

The natural range of the popular marine baitfish, Fundulus heteroclitus (mummichogs), spans the entire Atlantic coast of North America from Florida to Newfoundland, and a market already exists throughout. Few attempts have been made to culture this species on a commercial scale (Bradley 2001) to date. Demand remains high during seasonal lulls in wild supply and wholesale prices are high while bait prices remain low (Oesterling et al. 2004, Ohs et al. 2010), leaving a slim profit margins for bait retailers. Commercial culture of this species has gained interest in recent years but has yet to be fully developed due to lack of species-specific methods that focus on increasing yield and profitability.

Mummichogs are intertidal fractionally spawning teleost fish native to saltmarshes and estuaries. Spawning occurs in the days surrounding spring tides in as little as 10 cm of water (Taylor and DiMichele 1983), typically lasting from April to August. In the northern portion of the range the spawning season is typically condensed to three months where spawning periodicity is damped (McMullin et al. 2009) and occurs daily instead, typically during the highest tide of the day (Petersen et al. 2010). Daily spawning behavior of Maine populations has been observed repeatedly in less than 5 cm of water (Petersen et al. 2010). Spawning depth is likely related to egg survival since eggs laid high enough to be exposed during successive low tides avoid siltation or smothering (Taylor and DiMichele 1983), predation, and depressed oxygen levels.

Eggs are naturally stranded above the water line for days or weeks before being rewet. In fact, F. heteroclitus and F. grandis embryogenesis out of water has been shown to lead to improved development and healthier fry (Stockard 1907, Tingaud-Sequeira et al. 2009, Coulon et al. 2012) when compared to eggs that develop in water. Aquaculture techniques for Fundulus grandis have been developed which mimic this through aerial incubation (Coulon et al. 2012). Mummichog eggs developing at 20 degreesC are able to hatch as soon as 9.5 d after fertilization, when the mouth first opens (Armstrong and Child 1965). However, hatching may be postponed until the yolk sac has been completely absorbed, which could take up to 16 days (Armstrong and Child 1965). Considering this window for hatching and the benefits of aerial incubation it may be beneficial to remove freshly laid eggs from spawning tanks as soon as possible to optimize egg development and consequently fry production. However, the demand of a daily egg collecting regime would likely increase labor and material costs with uncertain increases in fry yield. For a small mummichog aquaculture entrepreneur, maximizing yield while minimizing labor costs is of utmost importance for a sustainable business.

Early production attempts for this species have largely relied on traditional methods for other bait species with similar behaviors and life cycles such as Notemigonus crysoleucas and F. grandis. However, culture methods should mimic the species natural conditions as closely as possible for optimal returns. Provided that F. heteroclitus select the shallowest water during the highest tides in which to spawn, it is plausible that egg collector depth may impact the quantity of eggs collected. In our previous studies, egg collection was successful with collectors placed 12 cm below the surface of the water in 5,000-L tanks on indoor recirculating systems. Green et al. (2010) maintained egg collectors at 8 cm below the water surface for effective collection of F. grandis eggs in 10,000-L outdoor pools. No specific observations of spawning depth minimum or maximum have been reported for wild populations of mummichogs, and whether or not these fish prefer to lay eggs in shallow depths in the absence of tidal fluctuations has never been tested.

The purpose of this study is to examine egg collection techniques for mummichogs on a semi-commercial-scale to optimize egg and fry production with minimal labor input. We chose to evaluate the effect of egg collector depth on production by placing collectors at different depths within spawning tanks. At the same time, we evaluated the amount of labor required to collect eggs at two different frequencies in order to determine a schedule that optimized fry yield and labor input.

Armstrong, P. B. and J. S. Child. 1965. Stages in the normal development of Fundulus heteroclitus. The Biological Bulletin: 128(2) 143-168.

Bradley, W. K. 2001. Final report: Intensive culture of the bait fish Fundulus heteroclitus. North Carolina Sea Grant 98-AM-05. Raleigh.

Coulon M. P., C. T. Gothreaux, and C. C. Green. 2012. Influence of substrate and salinity on air incubated Gulf killifish embryos. North American Journal of Aquaculture 74: 54-59.

Green, C. C., C. T. Gothreaux, and C. G. Lutz. 2010. Reproductive output of Gulf killifish at different stocking densities in static outdoor tanks. North American Journal of Aquaculture 72:321-331.

McMullin, V. A., K. R. Munkittrick, and D. A. Methven. 2009. Latitudinal variability in lunar spawning rhythms: absence of a lunar pattern in the northern mummichog Fundulus heteroclitus macrolepidotus. Journal of Fish Biology 75: 885-900.

Oesterling, M. J., C. M. Adams, and A. M. Lazur. 2004. Marine baitfish culture: workshop report on candidate species and consideration for commercial culture in the southeast U.S. Virginia Sea Grant Marine Resource Advisory Number 77. VSG-04-12. Gloucester Point.

Ohs, C. L., S. W. Grabe, S. M. DeSantis, M. A. DiMaggio, and A. L. Rhyne. 2010. Culture of pinfish at different stocking densities and salinities in recirculating aquaculture systems. North American Journal of Aquaculture 72: 132-140.

Petersen, C. W., S. Salinas, R. L. Preston, and G. W. Kidder III. 2010. Spawning periodicity and reproductive behavior of Fundulus heteroclitus in a New England salt marsh. Coepeia 2010(2): 203-210.

Stockard, C. R. 1907. The influences of external factors, chemical and physical, on the development of Fundulus heteroclitus. Science 25(646): 780-781.

Taylor, M. H. and L. DiMichele. 1983. Spawning site utilization in a Delaware population of Fundulus heteroclitus (Pisces: Cyprinodontidae). Copeia 1983(3): 719-725.

Tingaud-Sequeira, A., C. Zapater, F. Chauvigné, and J. Cerdà. 2009. Adaptive plasticity of killifish (Fundulus heteroclitus) embryos: dehydration-stimulated development and differential aquaporin-3 expression. American Journal of Physiology – Regulatory, Integrative, and Comparative Physiology 296: R1041-R1052.

Project Objectives:

Objective 1: Explore the effect of egg collector depth on egg production and viability. I have conducted and completed an experiment that examined the effect of egg collector depth on these dependent variables.

Objective 2: Explore egg collecting intervals to determine a sustainable labor cost-to-yield ratio. I have conducted and completed an experiment that examined the effect of egg collection frequency on this dependent variable.

Cooperators

Click linked name(s) to expand
  • Dennis McIntosh

Research

Materials and methods:

Broodstock Facility

This study was performed at the Delaware State University Aquaculture Research and Demonstration Facility in Dover, Delaware during the spring and summer of 2012. We obtained local, wild-sourced broodstock from a bait fisherman, supplemented by additional locally-sourced fish that had been held on-site in a freshwater pond. All fish were evenly mixed and stocked into each of 18 tanks on twin indoor recirculating systems. Fish were allowed to acclimate to tank conditions for six weeks prior to the start of the trial. At this point, 240 adult fish were in each tank.

Each of the recirculating systems consists of nine 1,000-L circular fiberglass tanks and is fitted with a 200-L sump, one 1.0-hp centrifugal pump (15UMF-S; Jacuzzi Brands, West Palm Beach, Florida), an inline 9-kw electric heater (DE9322; PSA Red Line, St. Barthelemy d’Anjou, France), a propeller-washed bead filter (PBF-10; Aquaculture Systems Technologies, New Orleans, Louisiana), and an ultraviolet (UV) sterilizer (E150S; Emperor Aquatics, Pottstown, Pennsylvania). Each tank is outfitted with one 10.2 x 3.8 air stone supplied with air from a common regenerative blower.

Salinity level was maintained at 10 g/L by diluting sterilized, full-strength seawater (31 +/- 2 g/L) with well water. Seawater was collected from the Indian River Inlet of the Delaware Bay and stored in on-site holding tanks. Raw seawater was disinfected by chlorinating with 10 mg/L Cl, aerating for 24 h, then removing residual chlorine with sodium thiosulfate. System water temperature was maintained at 26 degrees C and light was on a schedule of 14 h light: 10 h dark. Dissolved oxygen, pH, temperature, and salinity were measured daily using a YSI 556 multiprobe (YSI, Yellow Springs, Ohio). Alkalinity, as mg/L CaCO3, was monitored twice weekly using a YSI 9100 photometer. Other biweekly measurements were made using a Hach(registered trade mark) DR-2500 spectrophotometer (Hach Co., Loveland, Colorado) and included ammonia, nitrite, and nitrate. Tests were performed according to manufacturer’s instructions.

Broodstock were fed a commercially prepared 2.5 mm slow-sinking pellet (High performance mini-pellets, 40% crude protein, 13% crude lipid; Zeigler Brothers, Gardners, Pennsylvania) at a rate of 2% total biomass per day. This experiment was run for two full lunar cycles in order to capture an even amount of peaks and troughs within the natural periodicity of egg production (Taylor et al. 1979).

Egg Collection and Care

A total of six treatments were assessed for this experiment, each one was a unique combination of collector depth (8, 16, or 24 cm) and collection frequency (two or three times per week). Each treatment was assigned at random to three of the 18 tanks. Each tank contained one disk-style egg collector, a design based on the results from a previous trial (Janiak, in prep). The disk-style collector is composed of evenly distributed disks suspended on a horizontal axis. Disks were constructed of 6.35-mm black, high density polyethylene (HDPE), cut to 10 cm in diameter. Spacers between individual HPDE disks provided stability to the spindle and regular intervals of ample space for egg deposition. Spacers were made of 2.38-mm grey PVC and were 5 cm in diameter. Holes were drilled through the center of all disks and spacers so that each spindle was constructed of alternating HDPE/PVC disks and a 30 cm long section of 0.48-cm nylon all-thread fastened with nylon wingnuts. Each spindle contained 18 disks and 17 spacers. Egg collector design for this experiment was modified slightly from our earlier work to maximize collection efficiency. Each collector consisted of a pair of spindles was suspended inside of a 30 x 30 cm latex-coated wire mesh frame fitted with fixed cable ties to secure spindles (Figure 1). Collector frames were attached with rope to two floats made of capped 30 x 5 cm PVC pipes and adjusted to hang at the designated treatment depths.

At the specified intervals (two or three times per week), eggs were removed from collectors for incubation and the collectors were then returned to their respective tanks. Eggs were rinsed by pouring them over a 1.8-mm screen and rinsing with 10 g/L water until all small debris passed through the screen. The amount of time taken to remove eggs from the collectors, rinse them, and return the collector to the tank was recorded for each replicate to evaluate the labor requirements.

Unfertilized, opaque eggs were removed by hand and counted. The remaining fertilized eggs were then placed in a gridded petri dish. The petri dishes were placed on an opaque,surface so they could be photographed. Images were captured using a PowerShot SD1200 IS (Canon U.S.A., Lake Success, New York), and eggs were counted with ImageJ software (U. S. National Institutes of Health, Bethesda, Maryland). Promptly after photographing, fertilized eggs were placed in air incubation tubs (Coulon et al. 2012) constructed of 25 x 30 x 5 cm plastic storage bins with loose-fitting lids which were lined with two fitted pieces of 2.5-cm thick polyurethane hobby foam (Poly-fil Tru-Foam, Fairfield Processing Corp., Danbury, Connecticut). Eggs were spread in a single layer on the bottom piece of foam to minimize clumping and optimize oxygen availability (Armstrong and Child 1965). Eggs were incubated in tubs for 11-12 days at 26 degrees C in a 0.57 m3 Isotemp refrigerated incubator (Thermo Fisher Scientific, Waltham, Massachusetts) and misted with filtered, UV-sterilized 10 g/L water every other day. Placement of incubation tubs was randomized within the incubator. After incubation, hatching was initiated by removing eggs from the foam and immersing them in dishes filled with 10 g/L saltwater. Digital photographs of eggs and fry during hatching were taken using a Coolpix P7000 (Nikon, Melville, New York) and counted using ImageJ software.

Statistical Analysis

All statistical analyses were performed using JMP software version 9.0.2 (SAS Institute, Cary, North Carolina). Egg counts were square root transformed and analyzed using a two-way general linear model analysis of variance (ANOVA). Significant differences between treatments were identified specifically through post hoc Tukey-Kramer multiple comparisons analysis. The effect of collection regime on weekly fry yield and labor was examined using two tailed t-tests. Regression analyses were used to determine the relationship between total number of eggs and lunar period, as well as fry yield and labor. For all analyses, an ? value of 0.05 was used. Results are expressed as mean +/- SE.

Armstrong, P. B. and J. S. Child. 1965. Stages in the normal development of Fundulus heteroclitus. The Biological Bulletin: 128(2) 143-168.

Coulon M. P., C. T. Gothreaux, and C. C. Green. 2012. Influence of substrate and salinity on air incubated Gulf killifish embryos. North American Journal of Aquaculture 74: 54-59.

Taylor, M. H, G. J. Leach, L. DiMichele, W. M. Levitan, and W. F. Jacob. 1979. Lunar spawning cycle in the mummichog, Fundulus heteroclitus (Pisces: Cyprinodontidae). Copeia 1979(2): 291-297

Research results and discussion:

Over the eight week period a total of 161,324 eggs were collected from all 18 tanks, with eggs being successfully collected at all collector depths. Likewise, eggs were deposited equally among both spindles of the collectors. Neither depth nor frequency alone had an impact on total egg count (P ? 0.05), but the combined effect of depth and frequency was significant (P = 0.0481, Figure 2). The highest quantities of eggs were collected at the shallowest depth for the higher collection frequency, which was not significantly different from numbers collected at all depths for the lower collection frequency.

In the absence of tidal influence mummichogs still exhibited a preference for spawning in shallow water in the triweekly collection. It is possible that this was masked in the biweekly collection due to the courser scale of collection frequency. Intertidally spawning fish grown in large tanks or in an aquaculture facility have also exhibited peaks in egg production that correspond with natural spawning patterns linked to lunar cycles (Sherrill and Middaugh 1993, Green et al. 2010). This was also shown be the case for wild collected mummichogs in this experiment. The semilunar periodicity of egg deposition observed during these experiments reflects the natural egg deposition behavior of local, wild populations of F. h. heteroclitus (Taylor et al. 1979, Kneib 1986a). Since the instinctual behavior still appears to exist in the absence of tides, it is likely that northern populations of F. h. macrolepidus that lack the lunar periodicity (Wallace and Selman 1981, Petersen et al. 2010) and spawn instead during the highest tide of the day (Petersen et al. 2010) will also exhibit a preference to deposit eggs on shallower collectors. As long as broodstock are still collected from the wild, aquaculture methods that are adapted to the natural spawning elements of this species – such as shallow-placed egg collectors – should continue to maximize egg yield.

There was no significant difference in weekly fry yield between the collection regimes (7877 +/- 907 biweekly, 7378 +/- 887 triweekly; P ? 0.05). The weekly amount of time spent collecting eggs was significantly higher for the higher collection frequency (177.75 +/- 8.60 min) than the lower collection frequency (117.75 +/- 5.14 min; P < 0.0001). There was no relationship between increased effort and fry yield (P ? 0.05). Peaks in egg production were associated with lunar periodicity, specifically new and full moons (r2 = 0.12, P = 0.0284).

Removing eggs from collectors for aerial incubation more frequently did not lead to an increase in fry yield. This, coupled with the increased labor required, leads to the conclusion higher collection frequency leads to a decrease in efficiency. Since there was no increase in fry yield with increased effort there is no benefit to increasing the frequency of egg collection above twice per week. Taking into account that the price per unit for Fundulus bait is still low (Oesterling et al. 2004, Ohs et al. 2010), intensive culture operations must adopt methods that are the most labor-efficient and cost-effective.

Further benefits of bi-weekly egg collections include limiting cohorts of eggs to no more than three or four days apart in age. Maintaining minimal cohort age variation assures more even development and, since smaller conspecifics may be consumed (Kneib 1986b, Able and Hagan 2003, Able et al. 2007) may prevent cannibalism. Indeed, increased size variation within a cohort can lead to lower yields due to cannibalism (Kestemont et al. 2003). Uniform cohorts also promote accuracy in calculation estimations (Frechette 2005) including feed rationing. Cohort age differences could be minimized by more frequent collection, but given the lack of supporting evidence in this experiment that is not recommended. Alternatively, one collection per week would expand the cohort age variation up to seven days, increasing the difference in development profoundly (Armstrong and Child 1965). Such large variations in development could lead to uneven hatching rates. Since aerial incubation is best for production (Tingaud-Sequeira et al. 2009, Coulon et al. 2012), differential hatching will likely result in significant fry loss or an increase in the need for handling, again increasing the need for labor.

As interest in culturing this species increases, additional research will be required to identify species-specific methods that increase production and ultimately profitability. The results of this experiment provide some insight; fry yield will not increase with more frequent egg collection, and the number of eggs collected may be maximized by using shallow collectors. Intensive culture operations should adopt these procedures for the most efficient yield-to-labor ratio.

Able, K. W. and S. M. Hagan. 2003. Impact of common reed, Phragmites australis, on essential fish habitat: influence on reproduction, embryological development, and larval abundance of mummichog (Fundulus heteroclitus). Estuaries 26(1): 40-50.

Able, K. W., S. M. Hagan, K. Kovitvongsa, S. A. Brown, and J. C. Lamonaca. 2007. Piscivory by the mummichog (Fundulus heteroclitus): Evidence from the laboratory and salt marshes. Journal of Experimental Marine Biology and Ecology 345: 26-37.

Green, C. C., C. T. Gothreaux, and C. G. Lutz. 2010. Reproductive output of Gulf killifish at different stocking densities in static outdoor tanks. North American Journal of Aquaculture 72:321-331.

Armstrong, P. B. and J. S. Child. 1965. Stages in the normal development of Fundulus heteroclitus. The Biological Bulletin: 128(2) 143-168.

Coulon M. P., C. T. Gothreaux, and C. C. Green. 2012. Influence of substrate and salinity on air incubated Gulf killifish embryos. North American Journal of Aquaculture 74: 54-59.

Fréchette, M. 2005. A comment on the methodology of stocking experiments. Aquaculture 250: 291-299.

Kestemont, P., S. Jourdan, M. Houbart, C. Mélard, M. Paspatis, P. Fontaine, A. Cuvier, M. Kentouri, and E. Baras. 2003. Size heterogeneity, cannibalism and competition in cultured predatory fish larvae: biotic and abiotic influences. Aquaculture 227: 333-356.

Kneib, R. T. 1986a. The role of Fundulus heteroclitus in salt marsh trophic dynamics. American Zoologist 26(1): 259-269.

Kneib, R. T. 1986b. Size-specific patterns in the reproductive cycle of the killifish, Fundulus heteroclitus (Pisces: Fundulidae) from Sapelo Island, Georgia. Copeia 1986(2): 342-351.

Oesterling, M. J., C. M. Adams, and A. M. Lazur. 2004. Marine baitfish culture: workshop report on candidate species and consideration for commercial culture in the southeast U.S. Virginia Sea Grant Marine Resource Advisory Number 77. VSG-04-12. Gloucester Point.

Ohs, C. L., S, W. Grabe, S. M. DeSantis, M. A. DiMaggio, and A. L. Rhyne. 2010. Culture of pinfish at different stocking densities and salinities in recirculating aquaculture systems. North American Journal of Aquaculture 72: 132-140.

Research conclusions:

The results of the experiment conducted can directly benefit mummichog growers. Using the methods recommended (biweekly collection regime) producers can expect the highest egg yield with minimal labor costs. Mummichogs are still predominantly wild-caught due to relative abundance and lack of species-specific culture methods. During my experience working with this species I have noticed a distinct trend that there is a continued, increased interest in commercially producing this species. If the recommended methods are adopted, mummichogs can begin to be produced in aquaculture facilities and wild harvest can be minimized. The potential impacts of this scenario would be: 1) reduced environmental impact by wild-harvest of bait, and 2) increased economic stability for the marine baitfish industry and mummichog growers alike. Both would be considered positive outcomes.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

During this trial we were able to produce a large quantity of fry. Some of which were donated to a local high school. This donation helped strengthen a relationship with the educators at this school and since then I have visited the animal science class (about 20 students) to perform lectures and hands-on activities on two separate occasions. I have given a lecture to them discussing the need to farm these fish rather than rely on wild supply and emphasized the methods I have developed through this and other research I have conducted. In addition to fish and egg donations, I have provided them with hands-on experience on how to construct egg collectors for maximum yield and trained them on the efficient hatchery techniques I have developed. The animal science educator will be incorporating some of my research into her curriculum since she plans on keeping a population of these fish in her classroom for the foreseeable future. Many of her students are involved in Future Farmers of America or live on or near farms, so there is potential for this technology to be implemented or transferred indirectly through these students.

Every year, our program hosts a series of workshops, “Aquaculture 101,” that covers a variety of topics for those interested in aquaculture or looking to add to their skill portfolio. I developed one of these workshops to cover hatchery methods with specific emphasis on mummichog hatchery techniques, namely to transfer the research I have been conducting. I hosted the workshop at the Delaware State University Aquaculture Research and Demonstration Facility so that attendees could gain hands-on experience with the techniques we were covering. This workshop was advertised a number of ways: through mailers using my advisor’s mailing list for his aquaculture-related Cooperative Extension activities, the DSU Aquaculture Facebook page that I help to administer, on the DSU Cooperative Extension calendar, through the USDA Aquacontacts listserve administrated by Gary Jensen and Max Mayeaux, and by word of mouth. Of these, the mailer and email were most effective.

Our central location in Dover, Delaware drew 16 participants from five states: Delaware, Maryland, Virginia, Pennsylvania, and New Jersey. Over half of the participants (68%) were directly involved in some aspect of fish culture, ranging from the hobbiest scale, fish farm worker, entrepreneur, all the way up to commercial producer. We surveyed the attendees using a scale of 1 to 5 where 1 is the lowest and 5 is the highest. The average hatchery knowledge before was middle of the road, with a mean score of 2.3. After the workshop was complete the level of hatchery knowledge had greatly increased to 3.8. When asked if the material covered would improve their business, those currently involved in fish culture replied with an average of 4.5. For all attendees, the likelihood that the material covered in the workshop would help them to start a business was 3.5. In addition to gaining useful knowledge that could benefit their current or future fish farming businesses, attendees were extremely satisfied with the content of the workshop as the average response was 4.5 on the same scale.

In addition to the workshop, I authored a fact sheet on indoor hatchery methods for the mummichog. The purpose of the fact sheet is to one day be incorporated into a series of fact sheets on mummichog production and, eventually, a production manual for the species. The fact sheet covers many basic concepts about the hatchery phase of this species and includes recommendations based on this and my previous research. The fact sheet was distributed to the workshop attendees and is available through DSU Cooperative Extension.

Aspects of this study were presented at the Atlantic Estuarine Research Society meeting in October 2012 and the Northeast Aquaculture Conference and Exposition in December 2012. Total attendance for both meetings combined was over 500 individuals.

Project Outcomes

Project outcomes:

The biweekly egg collection regime was the most efficient as it required less labor to achieve the same yield as the higher collection frequency. It took 1.5 times longer to switch collectors at the higher frequency than the lower, biweekly frequency. This increased time directly translates to increased labor hours required for this step in production. If labor at this step can be reduced, more time is allowed for efficiently managing the remaining steps and production can theoretically be expanded or increased without increasing labor demands. Producers can expect the most revenue through an efficient labor to yield ratio by using collecting eggs twice per week. Fecundity of this marine baitfish is lower than many freshwater baitfishes (e.g., 2% of golden shiner egg production) so emphasis on methods that minimize labor costs and increase yield are essential for a sustainable business model for mummichog production.

Farmer Adoption

Farmers and extension agents that work with the baitfish industry have essentially told me the same thing: wholesale prices for this species are becoming unreasonably high yet aquaculture technology is not advanced enough to make farming profitable. I am unaware of any farmers that have adopted these techniques yet, though the spawning season for this species has not yet begun this year. For those farms just starting out with mummichog production, these methods minimize labor and increase yield due to improved egg collection compared to traditional collection techniques which are not as effective or efficient for this species.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Three things could be done to increase the sustainability of commercial mummichog production. The first, which directly builds on this work, would be exploration into sex ratios. We used mixed sex broodstock in this trial which is a common practice, though specific sex ratios of broodstock could lead to increased egg production. Second, insight into reduced salinity production using the northern, more freshwater tolerant, subpopulation of mummichogs (F. h. macrolepidotus) may lead to the elimination of a need for salt water. Salt water is expensive to make with the appropriate salts, coastal land and shipping seawater is also costly. Furthermore, maintenance of saltwater systems is more expensive than for freshwater. If the need for saltwater is eliminated, the range of mummichog production can be expanded inland and rely on the already well-established framework of the freshwater baitfish industry. Lastly, mummichogs are omnivorous and have to potential to grow and survive well on alternate ingredients. Exploration into alternative protein sources will significantly impact the sustainability of commercial production of mummichogs.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.