Farming Tautog as a High Value Fish while Reducing Invasive Crab Populations

Progress report for LNE19-393R

Project Type: Research Only
Funds awarded in 2019: $149,179.00
Projected End Date: 05/31/2021
Grant Recipient: Ward Aquafarms, LLC
Region: Northeast
State: Massachusetts
Project Leader:
Dr. Daniel Ward
Ward Aquafarms, LLC
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Project Information

Project Objective:

The goal of the proposed project is to develop the strategy, diet and growout techniques necessary to farm tautog, which is a high-value fish in the Northeast, using a natural fish feed utilizing green crabs, which are a discarded invasive marine species. Diversifying product offerings is a critical development goal of marine aquaculture farmers, and industry adoption will be facilitated by demonstrating an economically and environmentally sustainable method of farming tautog to interested stakeholders.

Introduction:

The development of new aquaculture species is paramount to the expansion of the domestic aquaculture industry.  Currently there are only a handful of well-developed aquaculture species (i.e. Atlantic salmon, trout, shrimp, tilapia, etc.), none of which are well suited to the Southern New England environment.  Developing local marine species will increase local production which will relieve pressure on wild populations, increase employment and economic opportunities as well as increase the overall production of seafood for local and export markets. 

 

Tautog (Tautoga onitis), also known as blackfish, are a coastal wrasse whose range extends from Massachusetts to Virginia.  Throughout their range, tautog is a highly sought-after species by commercial and recreational anglers.  Tautog have a firm white fillet which commands a high market price (average $4.35/lb live weight ex-vessel price in Massachusetts in 2017, data from MADMF).  While this is a lucrative fishery, supply is limited due to the current state of the resource.  The 2016 stock assessment listed all four sub-populations of tautog as overfished, with overfishing occurring throughout much of the range due to the high demand (ASMFC, 2016).  Abundance is at, or near historic lows, resulting in severe limitations on the wild fisheries. As such, availability has been limited to high-end restaurants and markets, with a live-market for small fish demanding the highest price. 

 

Tautog (Tautoga onitis) had previously been identified as a candidate for regional aquaculture (Perry et al. 1998).  Tautog are a robust and hardy fish, having a wide temperature (4⁰C – 30 ℃) and salinity tolerance.  Tautog tolerate high-density culture due to their life history as a reef-oriented species with strong site fidelity and low movement rates (Bigelow and Schroeder, 1953, Olla et al. 1974, Steimle and Shaheen, 1999).   As such there was early interest in the development of this species for aquaculture use.  The early excitement of this species was due to previous ecological work which indicated that juveniles appeared to exhibit high growth rates (Cooper, 1967).

 

Spawning induction and larval culture had been successfully done in the laboratory (Perry et al. 1998, Perry et al. 2001, Perry et al. 2008).  While the early life history work has been well studied, these trials documented relatively slow growth.  Perry et al. (2001) was able to spawn and grow juvenile tautog for 490 days.  Within this study, growth appeared to be linear from day 172 to 490 at a rate of 0.29 mm/day.  Similar rates were observed at the University of Rhode Island (0.35 mm/day, Perry et al. 2001).  Interestingly this contrasts with numerous studies of observed growth in the wild.  Sogard et al. (1992) observed juvenile tautog growing at an average of 0.5 mm/day in New Jersey.  Dorf et al. (1994) likewise observed growth rates of 0.54 mm/day in Narragansett Bay, Rhode Island.  While Martin (1993) observed similar growth in northern fish (0.5 mm/day in New Jersey and Rhode Island), fish in Virginia displayed growth rates of 1 mm/day, double that of their northern counterparts and 3-4 times that of those grown in the lab.  The difference in growth rates between northern and southern fish is theorized to be due an elongated growing season in warmer waters (Steimle and Shaheen, 1999, Mercaldo-Allen et al., 2006).  The difference in growth between lab and wild fish is highly unusual.  Perry et al. (2001) speculated that this could be due to an unknown missing nutritional component.  Fish in the labs were fed a standard high protein commercial diet.  These diets are typical for most commercial aquaculture species, however most commercial species are piscivorous, unlike tautog.  Martin (1993) was able to grow young of the year tautog in a lab at a rate of 0.7 mm/day on a diet of mysids.  This indicates that a natural feed may yield significantly improved growth rates.

 

Green crabs, Carcinus maenas, are an invasive species commonly found along the northeastern Atlantic and Pacific coasts.  The establishment of this species has resulted in a significant regional ecological disruption causing damage to local mussel beds, oyster reefs and eelgrass beds (Hughes and Elner, 1979, Grosholz et al., 1995, Young et al. 2017).  Most notable has been its local impact on the commercially important soft-shell clam, Mya arenaria.  The green crab is a voracious predator of soft-shell clams consuming up to 21.8 clams/crab/day (Floyd and Williams, 2004).  In Maine and Massachusetts the annual harvest of soft-shell clam has been shown to be inversely related to the abundance of green crabs (Young et al. 2017).  As a result several communities in northern Massachusetts, in collaboration with the Massachusetts Division of Marine Fisheries (MADMF), have established green crab trapping programs.  Additionally, the Maine Clammers Association started a “Five to Stay Alive” campaign which is encouraging all commercial clammers to actively fish 5 crab pots to reduce the green crab population.  While there has been an effort to create a market for green crab products, there has been little success.  The result is most of green crabs are thrown into landfills or composted.  The goal of this project was to create an alternative fish feed using green crabs.  Preliminary work at the University of Massachusetts Dartmouth has shown that juvenile tautog (as small as 10 g) readily eat chopped green crabs, have good survival and have exhibited good growth.  Further improvements in growth are possible with increased feed rations and warmer temperatures (compared to the current ambient temperature), and results indicate that it would be feasible to raise tautog to market size (~1 kg) in 18-24 months.

Cooperators

Click linked name(s) to expand
  • Christopher Rillahan (Researcher)
  • Michael Coute (Researcher)
  • Harrison Tobi (Researcher)

Research

Hypothesis:

Hypothesis 1: Tautog fed a natural diet will exhibit higher growth rates compared to a commercial fish feed. Will a diet based solely on green crab, or a mixed diet of green crab and commercial feed provide the best growth?

Hypothesis 2: Tautog can be grown to market size in 18-24 months on commercial shellfish farms, in either tanks or netpens. Will both methods of growout be commercially viable, or will fish grown at a higher consistent temperature exhibit higher growth rates, leading to greater economic viability?

Materials and methods:

During the month of April 2019, minnow traps baited with green crab were deployed in Megansett Harbor, MA (Figure 1, Location A). Traps were checked and rebaited every other day. However, the use of minnow traps proved highly inefficient with minimal to no weekly captures of tautog. Beach seining proved much more successful. During the months of May and June 2019 a series of beach seines were conducted at Megansett beach in North Falmouth, MA (Figure 1, Location A) and Monk’s Cove in Bourne, MA (Figure 1, Location B). Year 1 tautog ranging from 5.3 cm to 10.2 cm were kept from the beach seines and placed immediately in coolers upon capture. All bycatch was released back to the water at the respective sampling locations (Figure 1). Tautog within desired size rang (5 to 10 cm) were then transferred to lantern nets in Fiddlers Cove Marina in North Falmouth, MA, which in the same proximity as the Megansett Harbor sampling location (Figure 1, Location A).

Figure 1. Locations on Cape Cod, MA (A = Megansett Harbor; B = Monk’s Cove) where beach seines were conducted during the months of May and June of 2019 to obtain tautog.

            All captured tautog were kept in lantern nets for at least 24 hours prior to transportation to UMASS Dartmouth wet lab location in New Bedford, MA. Until the required number of tautog were acquired (450 individuals) via beach seining, they were held in a flow through system at the wet lab facilities in New Bedford, MA. Once over 450 tautog had been transferred to the wet lab facilities, the tautog were divided into three separate treatment diets: 1) Natural: green crabs only; 2) Zeigler: commercially available marine finfish diet; 3) Natural + Zeigler: green crabs supplemented with commercial feed. At the initiation of the experiment, the 450 tautog used had a mean length of 7.9 cm (SE±0.1) ranging from 5.3 to 10.2 cm/individual and a mean weight of 7.3 grams (SE±0.2) ranging from 2 to 19 grams/individual. Each treatment was composed of three replicate 75L flow through tanks housing 50 tautog each. The replicate tanks had controlled temperature (~25oC), salinity (30-32 psu), lighting (12L:12D) and aeration. Every 30 days, all tautog from each replicate were sampled for total length (cm) and weight (g). Additionally, while the tautog were being measured from each replicate, the tanks housing the replicates being measured were scrubbed of algae and then drained to promote aquaria cleanliness. Once tanks had fully drained and had fresh saltwater flow, the sampled tautog were returned to the respective tanks.

            Feeding amounts were determined based on satiation and administered at each feeding interval. Increases in feeding were decided based on percent growth and satiation. Satiation was determined by whether there was any left-over food left in the tanks after feeding. Table 1 shows the 3 different commercial pellet feeds that have been used up to this point in the study. From July to October, we used the ‘starter with Vpak’, and we fed 10 grams per feeding, twice a day. For the first two weeks in October, we used a half and half blend of the starter feed with the fingerling starter feed to ensure that the fish of different sizes were receiving food. From October 17, 2019 to January 4, 2020 we used the ‘fingerling starter with Vpak’. The fish received 20 grams of this food, per feeding. Starting on January 5, 2020, we began to use the ‘Hi-Performance’ marine finfish food from Zeigler. The amount was 30 grams of food, twice a day. The amount of food was determined by 2% of the total body weight and observational record of uneaten food in the tanks.

Zeigler Commercial Marine Finfish Food

 

Protein (%)

Fat

(%)

Fiber (%)

Moisture (%)

Ash (%)

Phosphorous

(%)

Starter w/ VPak

 (crumble #2)

55

15

1

12

12

1.8

Fingerling starter w/ VPak

(1.5-2.0 mm)

50

15

1.5

12

12

1.8

Finfish Hi-Performance

(2.5 mm)

45

16

1.3

12

10

1.4

Table 1: Zeigler commercial feed composition and size used in this study

            The amount of crab was determined by a total of 40% of the total weight of the fish, while also keeping track of whether or not all the food was being eaten in the tanks. Feeding to satiation while avoiding excess food in the tanks was important to ensure high water quality and growth. The amount of crab administered at each feeding, per month, is shown below in Table 2.

Month 

Crab (g)

July

200

September

400

October

650

November

650

December

1000

January

1000

Table 2: amount of crab administered each month, per feeding

            Statistical analyses were conducted in RStudio. Data of the mean daily growth rates, both in weight and length, of tautog from all three treatment groups for each sampling month were first tested for normal data distribution using a Shipiro-Wilks normality test. If data was normally distributed, an ANOVA was first conducted, and if a significant difference was present in the treatment groups, a Tukey post-hoc test was conducted. If the data was not normally distributed, then a Kruskal-Wallis test was conducted followed by Pair-Wise Wilcoxon post-hoc test.

Part 2: The Effects of Feed Attractants on the Growth of Tautog (Tautoga onitis) in Recirculating Aquaculture Systems

 

Justification

 

              Worldwide, aquaculture growth and development are greater than any other food production sector, while the FAO monitoring of marine fishery resources has shown that landings are continuing to decline (FAO 2018). With declining fishery resources, the world must face the challenge of feeding its growing population. The growing industry of aquaculture has a wide range of impacts, and contributes to food security, employment, enhanced resource management, and sustainable farm practices (Halwart et al., 2003) Sustainable farm practices are a key initiative for stakeholders, managers, and farmers moving forward. Limitations in production, high prices of fish meal and fish oil, and increasing concern for environmental impact have prompted a desire to seek alternatives to fuel the aquaculture industry (Nagel et al., 2017;Tantikitti 2014;). Feed alone contributes to more than 50% of the cost production in intensive aquaculture systems, and is often the single greatest expense in aquaculture systems (Pavadi et al., 2012; Fast et al., 1997) Aquaculture expansion is reliant on systems that favor readily available species that are preferred for local consumption (Halwart et al., 2003). In the United States, this is a challenge worth addressing in terms of ecological impacts and sustainability of the growing aquaculture initiative.

              Tautog (Tautoga onitis) is a marine wrasse native to western Atlantic communities, and extends from Nova Scotia to South Carolina, with the highest abundances noted from south of Cape Cod to the Delaware Capes (Bigelow and Schroeder 1953). Tautog exhibit strong site fidelity, low daily movement rates, and seasonal migration (Olla et al., 1974). These life history characteristics make this species vulnerable to fishing activity. From the most recent stock assessment produced by the Atlantic States Marine Fisheries Commission, (ASMFC) tautog have been identified as a species that is recreationally and commercially overfished, and overfishing is occurring (ASMFC 2017). Regional markets have supported recreational and commercial fishing of tautog for over a century. Records have shown that tautog appeared in fish markets in Boston as early as 1814, and in Wellfleet, hook and line fisheries have existed at least since 1839 (Bigelow and Schroeder 1953).

              Due to its life history characteristics, fish market potential, and fishing pressures, tautog have been identified as an ideal candidate for marine aquaculture (Perry et al., 1998). Laboratory studies of tautog have shown that adults can be conditioned to induce natural spawning, and success has been noted in multiple locations in Rhode Island and Connecticut (Perry et al., 1998). A year-round supply of high-quality, market preferred fish would boost regional economies, and could relieve fishing pressures. Growth rates in laboratory studies have been shown to be significantly lower than in the wild, and authors have acknowledged a potential missing component in the commercial feed (Perry et al., 2001). A nutritional component may be contributing to low growth rates in juvenile tautog, however, other components of food and feeding behavior may also be a factor.

              Poor attract -ability and palatability may be responsible for poor ingestion rates in some fish species (Ajiboye et al., 2012). In order to enhance these aspects of the finfish diet at a commercial scale, feed additives may provide a solution. Micro-bound particles allow for nutrients to bind and create a stable feed, examples of these include alginate, agar, carrageenan, starch, zein, and gelatin. This approach offers the advantages of economic viability and the not using toxic ingredients in order to make the food (Langdon 2003). Feed attractants have the potential to reduce feed waste, promote growth, and subsequently enhance the economic success of finfish aquaculture (Pavadi et al., 2012).

              Various studies have documented the trials of feed attractants on various species that have also been noted to have regional economic importance and market potential. In particular, hydrolysis has been employed as a promising way for the conversion of fish-by-products into new and suitable forms (Khosravi et al., 2015) Low molecular weight and well balanced amino acid profiles have made hydrolysates a viable chemo-attractant and fish meal replacement in aquafeeds(Aksenes et al., 2006a; Kolkovski et al., 2000). Gelatin bound squid hydrolysates have been used in the aquaculture of cod and octopus with success (Kvåle et al., 2006; Quintana et al., 2008). Hydrolysis breaks down large protein chains into peptides and free amino acids.  Feeding behavior is stimulated by low molecular weight substances with higher solubility(Løkkeborg et al., 2014) Inclusion of hydrolysates as protein replacement may have a two-fold effect; one being that ingestion rates become higher and two being that there is higher assimilation due to the free amino acid and short peptides ( Kolkovski et al., 2000).

              Olfactory and gustatory systems are the main centers for chemoreception in fish, odors may trigger food search, gustatory system may reject the object after tasting it (Løkkeborg et al., 2014).  Feed attractants are chemicals that orient an animal towards the source of the chemicals (Pavadi et al., 2012). Feed palatability in carnivorous aquaculture species shares a strong relationship with attractants that are associated with the prey components under wild conditions (Tantikitti 2014). When considering potential hydrolysates for tautog aquaculture, green crab may provide a solution, due to natural feeding habits. Dietary extracts from the tissues of prey species have been shown to stimulate feeding behavior (Løkkeborg et al., 2014). Further supporting this are studies documenting the success of crustacean meals in several aquaculture species, exhibiting positive results on palatability and growth performance (Toppe et al., 2006; Tibbets & Lall, 2013). In addition, attractants may provide a useful use of an otherwise underutilized marine resource.

Research Objective

The aims of this proposed project are to determine the role of feed attractants in the growth of tautog in recirculating aquaculture systems. In order to achieve this research goal, the proposed project will identify alternative sources of protein to inform the aquaculture community of potential replacements for fish meal and fish oil as a primary protein source. This portion of the project is also being used for the MSc thesis for graduate student Michael Coute to be completed at the University of Massachusetts Dartmouth School for Marine Science & Technology.

 

Methods

Due to the outbreak of the novel corona virus, laboratory operations were interrupted indefinitely, and regular access to the juvenile tautog we were working with was prohibited by institutional and regulatory forces. Additionally, health concerns kept the majority of personnel quarantined, despite no cases of COVID-19 in our research group. This unprecedented set of circumstances effectively ended the first feeding trial.

 

After resuming laboratory activities, it was determined that a second feeding study should be undertaken to assess the role of feed attractants and the effects on tautog growth. In June 2020, 450 year-1 (5-15 g) tautog will be collected locally from Buzzards Bay, which hosts a relatively large population of fish which can be obtained by beach seine. The fish will be brought to UMASS Saltwater Facility (New Bedford, MA) and introduced to a tank with flow-through seawater to acclimate. After 14 days, the fish will be introduced to a heated saltwater recirculating system of 300-gallon aquaria with controlled temperature (20° C), lighting (12L:12D), constant salinity (30-32 psu) and aeration. The fish will be separated into one of the three treatments (135 fish per treatment), each tank with 45 fish maintained in triplicate. The tautog will be fed to satiation twice daily (08:00, and 16:00), with one of the three diets. Once all the fish are placed into tanks randomly, they be assigned one of three possible feeding treatments: crab hydrolysate, squid hydrolysate, or commercial feed. This will result in triplicates of each diet. Feed will be created on site through the process of hydrolysis. All feed treatments will consist of a 1.5mm standard commercial pellet purchased from Ziegler fish foods (Table 1). The pellets will be coated in a non-flavored gelatin to ensure that the test variable is the hydrolysate. The designed feeding trials will take place over 12 weeks, with growth measurements for total length and weight taken biweekly to assess growth over time.

Research results and discussion:

Results:

Mean daily growth rates (weight)

            For sampling period one (July 2019 – September 2019), observed mean daily growth rates in weight (g) were 0.32 g/day (SE±0.02) for tautog fed a green crab only diet, 19 g/day (SE±0.01) for tautog fed a diet of both green crab and feed and 0.1 g/day (SE±0.01) for tautog fed a feed only diet, which was significantly less than the growth rate observed in the green crab only diet (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, p = 0.026, Figure 2). For sampling period two (September 2019 – October 2019), the observed mean daily tautog growth rate was 0.33 g/day (SE±0.04) for the feed only treatment, which was significantly lower than 0.52 g/day (SE±0.05) for the green crab only treatment (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, p = 0.026, Figure 2). The mean daily growth rate of 0.43 g/day (SE±0.4) observed for the tautog fed the green crab/feed treatment in sampling period two did not significantly vary from the other two feeding treatments (Figure 2). Mean daily growth rate for sampling period three was 0.76 g/day (SE±0.07) for tautog fed a green crab only diet, 0.51 g/day (SE±0.5) for tautog fed a diet of crab and feed and 0.36 g/day (SE±0.05) for tautog fed a feed only diet, which was significantly lower than the observed tautog growth rates in the crab only and mixed crab/feed treatments (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, p < 0.05, Figure 2). In the fourth sampling period (November 2019 – December 2019), tautog fed a feed only diet had a mean daily growth rate of 0.44 g/day (SE±0.07), which was significantly lower than a mean daily growth rate of 0.88 g/day (SE±0.09) for tautog fed a green crab only diet (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, P = 0.0044, Figure 2) and 0.76 g/day (SE±0.08) for tautog fed a mixed diet of green crab and feed (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, P = 0.014, Figure 2). Tautog fed a diet of only green crab in sampling period five (December 2019 – January 2020) had a mean daily growth rate of 0.92 g/day (SE±0.12), which was significantly higher (Tukey HSE, α=0.05, df =2, 410, P = 0.008) than 0.49 g/day (SE±0.08) observed in tautog fed a diet of only feed (Figure 2). Tautog fed a mixed diet of green crab and feed in sampling period five had a mean daily growth rate 0.61 g/day (SE±0.09), which was not significantly different from the growth rates observed in the two other feeding treatments (Figure 2).

Figure 2. Mean daily growth rates (g/day) of tautog fed a diet of green crab only (Crab/Crab), a mixed diet (Crab/Feed) and a diet of only commercially available fish feed (Feed/Feed) for the sampling months of September 2019 through January 2020.

Mean daily growth rates (length)

            Mean daily growth rate in length (cm/day) for sampling period one (July 2019 – September 2019) did not significantly vary (Kruskal-Wallis Rank Sum Test, χ2 = 5.58, df = 2, n = 410, p = 0.06153, Figure 3). Mean daily growth rates for sampling period one were 0.05 cm/day (SE±0.00) for tautog fed a diet of only green crab, 0.04 cm/day (SE±0.00) for tautog fed both green crab and feed and 0.03 cm/day (SE±0.00) for tautog fed an feed only diet (Figure 3). The mean daily tautog growth rate in length for the second sampling period (September 2019 – October 2019) was 0.06 cm/day (SE±0.01) for the green crab only diet, which was significantly greater (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, p = 0.017) than 0.04 cm/day (SE±0.01) observed for tautog fed the feed only diet (Figure 3). However, the observed mean daily growth rate of 0.05 cm/day (SE±0.00) observed for tautog fed the crab/feed diet did not significantly vary from tautog fed a diet of green crab only, and feed only (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, p = 0.235, Figure 3). For sampling period three (October – November 2019), the mean daily growth rate was 0.07 cm/day (SE±0.01) for tautog fed a diet of only green crab, which was significantly greater (Pairwise Wilcoxon Rank Sum Test, df = 2, n = 410, p = 0.0048) than 0.04 cm/day (SE±0.01) for tautog fed a feed only diet (Figure 3). Tautog in sampling period three that were fed a mixed diet of green crab and feed had a mean daily growth rate 0.05 cm/day (SE±0.00), which was not significantly different than the growth rates observed in the other two treatments (Figure 3). The mean daily growth rates for tautog fed a green crab only diet and a diet of green crab and feed in the fourth sampling period (November 2019 – December 2019) were both 0.06 cm/day (SE±0.01) and both of which were significantly higher (Tukey HSE, α=0.05, df =2, 410, P < 0.05) than 0.04 cm/day (SE±0.00) for tautog fed a feed only diet (Figure 3). For sampling period five (December 2019 – January 2020), tautog fed a diet of only green crab had mean daily growth rate of 0.06 cm/day (SE±0.01), which was significantly greater (Tukey HSE, α=0.05, df =2, 410, P = 0.0260) than 0.04 cm/day (SE±0.01) observed in tautog fed a diet of only feed (Figure 3). Tautog fed a mixed diet in sampling period five had a mean daily growth rate of 0.05 cm/day (SE±0.00), which was not significantly different the mean daily growth rates observed in tautog fed either a diet of only green crab or a diet of only feed (Figure 3).

Figure 3. Mean daily growth rates (cm/day) of tautog fed a diet of green crab only (Crab/Crab), a mixed diet (Crab/Feed) and a diet of only commercially available fish feed (Feed/Feed) for the sampling months of September 2019 through January 2020.

Discussion:

            Results from this study indicate that the use of green crab in the diet of aquacultured tautog may be a successful method at significantly increasing production yield compared to a diet comprised of currently available commercial fish feeds. In every sampling month, form September 2019 through January 2020, tautog fed a diet of comprised of only green crab had significantly higher daily growth rates in weight (g) than tautog fed comprised diet of only commercially available fish feed. The mean daily growth rates (g/day) of tautog fed a mixed diet of commercially available fish feed and green crab were less than those fed a green crab only diet. However, the growth rates (g/day) of tautog fed a mixed diet were higher than tautog fed a diet of only commercially available fish feed, reinforcing the observation that a diet of green crab may promoting increased production in tautog aquaculture. The significant increase in weight gain (g/day) in tautog fed a green crab only diet compared to tautog fed a diet of only commercially available fish feed may be due to a variety of factors. Factors leading to higher growth rates in tautog fed a green crab diet could be due to the green crab having a higher nutritional value, a more attractive scent, a longer period in which it is desirable for consumption compared commercial pellet food, or a variety of other factors. Instances of mortality have been much higher for tautog fed a diet solely consisting of commercial fish feed. This supports the argument that green crab may have a higher nutritional value. Further research will be needed to elucidate what exactly is leading to increased growth when tautog are fed a green crab diet as well as a way to make processing green crab viable on a commercial production scale.

 

Weight & Length

Preliminary results were generated using R Programming Language, and Analysis of Variance (ANOVA) tests were used to determine if the weight (g) and length (mm) were significantly different at the end of the feeding trial.

ANOVA tests revealed that length (mm) was not significantly different among tanks (DF=8, Sum Sq= 3259, Mean Sq= 407.4, F Value= 1.145, Pr(>F)= 0.333). Additionally, weight (g) was not significantly different among tanks after running an ANOVA on the final recorded values (DF= 8, Sum Sq= 3827, Mean Sq= 478.4,  F Value= 1.335, Pr(>F)= 0.226).

Figure 4: Tautog length distributions at the end of the feeding trial (sampling period 8) with outlier points highlighted by red points. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

Figure 5: Tautog weight distributions at the end of the feeding trial (sampling period 8) with outlier points highlighted by red points. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

Growth Rates

ANOVA tests were used to confirm no significant differences in the growth rate of tautog in length (mm/day) (DF=8, Sum Sq= 0.0784, Mean Sq= 0.009798, F Value= 0.333, Pr(>F)0.949). The same test was performed for weight gain (g/day) and resulted in no significant differences (DF=8, Sum Sq= 0.0805, Mean Sq= 0.01006, F Value= 0.891, Pr(>F)= 0.53).

Figure 6: Plot showing the average growth rates of tautog (mm/day) over the course of the feeding trial. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

Figure 7: Plot showing the average growth rates of tautog (g/day) over the course of the feeding trial. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

 

Discussion:

Results were determined to not be significant among any of the weights or lengths at the terminus of the feeding trial. It appears that feed attractants do not play a significant role in influencing the growth rates of tautog in recirculating aquaculture systems. Through both parts of our feeding trials so far, we have learned that using green crab as a natural diet is one way to significantly improve the growth rates of juvenile tautog in aquaculture systems, however the amount required of green crab required to produce market quality deliverables would be damaging to water quality in the natural environment or in the recirculating system. Using green crab at this time does not appear to be commercially viable, and further steps must be taken in order to explore and refine the farming techniques for tautog.

 

Weight & Length

Preliminary results were generated using R Programming Language, and Analysis of Variance (ANOVA) tests were used to determine if the weight (g) and length (mm) were significantly different at the end of the feeding trial.

ANOVA tests revealed that length (mm) was not significantly different among tanks (DF=8, Sum Sq= 3259, Mean Sq= 407.4, F Value= 1.145, Pr(>F)= 0.333). Additionally, weight (g) was not significantly different among tanks after running an ANOVA on the final recorded values (DF= 8, Sum Sq= 3827, Mean Sq= 478.4,  F Value= 1.335, Pr(>F)= 0.226).

Figure 4: Tautog length distributions at the end of the feeding trial (sampling period 8) with outlier points highlighted by red points. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

Figure 5: Tautog weight distributions at the end of the feeding trial (sampling period 8) with outlier points highlighted by red points. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

Growth Rates

ANOVA tests were used to confirm no significant differences in the growth rate of tautog in length (mm/day) (DF=8, Sum Sq= 0.0784, Mean Sq= 0.009798, F Value= 0.333, Pr(>F)0.949). The same test was performed for weight gain (g/day) and resulted in no significant differences (DF=8, Sum Sq= 0.0805, Mean Sq= 0.01006, F Value= 0.891, Pr(>F)= 0.53).

Figure 6: Plot showing the average growth rates of tautog (mm/day) over the course of the feeding trial. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

Figure 7: Plot showing the average growth rates of tautog (g/day) over the course of the feeding trial. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

 

Discussion:

Results were determined to not be significant among any of the weights or lengths at the terminus of the feeding trial. It appears that feed attractants do not play a significant role in influencing the growth rates of tautog in recirculating aquaculture systems. Through both parts of our feeding trials so far, we have learned that using green crab as a natural diet is one way to significantly improve the growth rates of juvenile tautog in aquaculture systems, however the amount required of green crab required to produce market quality deliverables would be damaging to water quality in the natural environment or in the recirculating system. Using green crab at this time does not appear to be commercially viable, and further steps must be taken in order to explore and refine the farming techniques for tautog.

Part 2:

Weight & Length

Preliminary results were generated using R Programming Language, and Analysis of Variance (ANOVA) tests were used to determine if the weight (g) and length (mm) were significantly different at the end of the feeding trial.

ANOVA tests revealed that length (mm) was not significantly different among tanks (DF=8, Sum Sq= 3259, Mean Sq= 407.4, F Value= 1.145, Pr(>F)= 0.333). Additionally, weight (g) was not significantly different among tanks after running an ANOVA on the final recorded values (DF= 8, Sum Sq= 3827, Mean Sq= 478.4,  F Value= 1.335, Pr(>F)= 0.226).

Figure 4: Tautog length distributions at the end of the feeding trial (sampling period 8) with outlier points highlighted by red points. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.
Figure 5: Tautog weight distributions at the end of the feeding trial (sampling period 8) with outlier points highlighted by red points. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

 

Growth Rates

ANOVA tests were used to confirm no significant differences in the growth rate of tautog in length (mm/day) (DF=8, Sum Sq= 0.0784, Mean Sq= 0.009798, F Value= 0.333, Pr(>F)0.949). The same test was performed for weight gain (g/day) and resulted in no significant differences (DF=8, Sum Sq= 0.0805, Mean Sq= 0.01006, F Value= 0.891, Pr(>F)= 0.53).

Figure 6: Plot showing the average growth rates of tautog (mm/day) over the course of the feeding trial. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.
Figure 7: Plot showing the average growth rates of tautog (g/day) over the course of the feeding trial. Control diet was flavorless gelatin coated pellets, crab diet utilized green crab hydrolysate, and the squid diet utilized squid hydrolysate as part of the flavorless gelatin coating.

 

Discussion:

Results were determined to not be significant among any of the weights or lengths at the terminus of the feeding trial. It appears that feed attractants do not play a significant role in influencing the growth rates of tautog in recirculating aquaculture systems. Through both parts of our feeding trials so far, we have learned that using green crab as a natural diet is one way to significantly improve the growth rates of juvenile tautog in aquaculture systems, however the amount required of green crab required to produce market quality deliverables would be damaging to water quality in the natural environment or in the recirculating system. Using green crab at this time does not appear to be commercially viable, and further steps must be taken in order to explore and refine the farming techniques for tautog.

Participation Summary
3 Farmers participating in research
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.