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CHARACTERIZATION OF THE STRIPED MULLET (MUGIL CEPHALUS) IN SOUTHWEST FLORIDA: INFLUENCE OF FISHERS AND ENVIRONMENTAL FACTORS
______
A Thesis
Presented to
The Faculty of the College of Arts and Sciences
Florida Gulf Coast University
In Partial Fulfillment
of the requirements for the degree of
Master of Science
______
By
Charlotte Marin
2018
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APPROVAL SHEET
This thesis is submitted in partial fulfillment of
the requirements for the degree of
Masters of Science
______Charlotte A. Marin
Approved: 2018
______S. Gregory Tolley, Ph.D. Committee Chair
______Richard Cody, Ph.D.
______Edwin M. Everham III, Ph.D.
The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline.
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ACKNOWLEDGMENTS
I would like to dedicate this project to Harvey and Kathryn Klinger, my loving grandparents, to whom I can attribute my love of fishing and passion for the environment. I would like to express my sincere gratitude to my mom, Kathy, for providing a solid educational foundation that has prepared me to reach this milestone and inspired me to continuously learn. I would also like to thank my aunt, Deb, for always supporting my career aspirations and encouraging me to follow my dreams. I would like to thank my in-laws, Carlos and Dora, for their enthusiasm and generosity in babysitting hours and for always wishing the best for me. To my son, Leo, the light of my life, who inspires me every day to keep learning and growing, to set the best example for him. To my husband, Sebastian, who unconditionally supports all my ambitious ideas and goals, and for always allowing me to be myself.
I would like to give special thanks to the fishermen and now friends, for participating in this study, including Skeeter, Terry Earnest, Bobby Greene, Kenny Jenkins, Mike Davis, Dwight Andress, Jimmy Bear, and in loving memory of David Godwin, who has since passed away.
I would like to thank the following employees of FWRI: Behzad Mahmoudi, my kindred spirit in the mullet world, for helping me design the project; my supervisors Chris Bradshaw and Steve Brown for their continuous support and flexibility throughout this journey and allowing me the opportunity for simultaneous work and study.
I would like to acknowledge Fish Florida and the International Women’s Fishing association for their financial assistance and ongoing efforts to support research in the field.
Finally, I would like to thank the members of my committee. First, to Richard Cody, an excellent team leader and forefront scientist in fisheries who continuously inspires me. I want to thank Richard for allowing me to explore my passions in the field and for the opportunity to work at a job I truly love. I would like to thank Win Everham
iv for radiating positivity, being an absolute delight and inspiration in the classroom, and for jumping on board as my committee member during the final leg. Most of all I would like to acknowledge my advisor, Greg Tolley, whom I will never be able to thank enough. Sometimes it only takes one person to see your potential and give you an opportunity that can change your life. Greg has been that person for me, and I am beyond grateful for his guidance, professionalism, charisma, and for this experience.
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TABLE OF CONTENTS
CHAPTER 1: CHARACTERIZATION OF THE STRIPED MULLET (MUGIL CEPHALUS) FISHING INDUSTRY IN SOUTHWEST FLORIDA ...... 1
INTRODUCTION ...... 1
HISTORICAL DEVELOPMENT OF FISHERY ...... 1
REGULATIONS AND POLITICS OF FISHING: NET BAN ...... 10
Consequences of the Net Ban ...... 18
Trends in Landings ...... 20
CURRENT STRIPED MULLET (MUGIL CEPHALUS) FISHERY AND ROE SEASON ...... 23
Management ...... 23
Fishing Methods ...... 25
Food Fish vs. Delicacy ...... 29
Fish Processing ...... 30
Fish Distribution ...... 33
Recent Trends in the Fishery ...... 34
IS AQUACULTURE THE SOLUTION? ...... 38
TABLES ...... 44
FIGURES ...... 50
REFERENCES ...... 59
CHAPTER 2: SEASONAL VARIATION OF THE COMMERCIAL STRIPED MULLET (MUGIL CEPHALUS) FISHERY IN SARASOTA BAY AND CHARLOTTE HARBOR: THE EFFECTS OF ENVIRONMENTAL VARIABILITY AND FISHERY-DEPENDENT FACTORS ON CATCH RATES 68
INTRODUCTION ...... 68
Taxonomy ...... 70
Biogeography ...... 71
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Habitat and Movement ...... 72
Feeding ...... 73
Age and Growth ...... 73
Reproduction ...... 75
MATERIALS & METHODS ...... 77
Study Area ...... 77
RESULTS...... 81
DISCUSSION ...... 85
TABLES ...... 93
FIGURES ...... 97
REFERENCES ...... 130
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LIST OF TABLES
Table 1.1 Florida Commercial Mullet Landings 1984-2015...... 44
Table 1.2. Total Mugil cephalus imported by various countries, 2010−2015...... 46
Table 1.3. Statewide total M. cephalus licenses and landings by year (2010–2015). (Data courtesy Steve Brown FWRI Fishery Dependent Monitoring)...... 47
Table 1.4 County-wide distribution of total red and white roe landings, total M. cephalus landings, average number of M. cephalus fishing trips, and average number of registered licenses with mullet landings per (2010–2015). (Data courtesy Steve Brown FWRI Fisheries Dependent Monitoring)...... 48
Table 2.1. Commercial M. cephalus sampling trips September 2012-January 2014...... 93
Table 2.2. Mean and standard errors of environmental variables by location...... 95
Table 2.3. Species caught and percentage of total catch...... 96
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LIST OF FIGURES
Figure 1.1 Florida statewide M. cephalus landings by year 1984-2015...... 50
Figure 1.2 Mullet fishermen during roe season in Big Pass, Sarasota...... 51
Figure 1.3 Traditional mullet skiff (photo courtesy of Steven Ball)...... 51
Figure 1.4 Traditional well boat (photo courtesy of Kracker Built Boat Works)...... 52
Figure 1.5 Use of hoop net during roe season (photo courtesy of Kenny Jenkins)...... 52
Figure 1.6 Harvested red roe at AP Bell Seafood Co...... 53
Figure 1.7. Number of registered licenses in study area by county and year 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring)...... 54
Figure 1.8. Total number of M. cephalus fishing trips in study area by county and year 2010-2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring)...... 55
Figure 1.9. Number of M. cephalus fishing trips in study area by gear and county 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring)...... 56
Figure 1.10. Total M. cephalus landings in study area by county and year 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring)...... 57
Figure 1.11. Total red and white roe M. cephalus landings in study area by county 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring)...... 58
Figure 2.1. Map of the study area and sampling stations...... 97
Figure 2.2. Results of linear regression comparing M. cephalus catches (Ln X + 1) and air temperature (R2=0.045, p<0.0145, n=131)...... 98
Figure 2.3. Results of linear regression comparing M. curema catch (Ln X + 1) and air temperature (R2=0.043, p<0.0170, n=131)...... 99
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Figure 2.4. Results of linear regression comparing M. curema catch (Ln X + 1) and water temperature (R2= p<0.041, n=136)...... 100
Figure 2.5. Results of linear regression comparing total fish (all species) catch (Ln X + 1) compared to dissolved oxygen (R2=0.033, p<0.0269, n=124)...... 101
Figure 2.6. Results of ANOVA comparing mean catch of M. cephalus (Ln X + 1) per set and time of day. Vertical bars are standard errors. Letters denote significant differences
(F5, 136=2.49, p<0.0462). Numbers denote number of sets. No sets were made 0100-0400 hrs...... 102
Figure 2.7. Results of ANOVA comparing mean number of fish (all species) per set and bottom type. Vertical bars are standard errors. Letters denote significant differences (F3,
126 = 2.81, p<0.0420). Numbers denote number of sets...... 103
Figure 2.8. Results of ANOVA comparing mean number M. curema (Ln X + 1) per set and bottom type. Vertical bars are standard errors. Letters denote significant differences (F3,
126 = 3.18, p<0.0264). Numbers denote number of sets...... 104
Figure 2.9. Results of ANOVA comparing mean number of M. curema per set and moon phase. Vertical bars are standard errors. Letters denote significant differences (F7,129 = 6.84, p<0.0001). Numbers denote number of sets...... 105
Figure 2.10. Results of ANOVA comparing mean number of fish (all species) per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =27.15, p<0.0001). Numbers denote number of sets...... 106
Figure 2.11. Results of ANOVA comparing mean number of M. cephalus per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =13.60, p<0.0001). Numbers denote number of sets...... 107
Figure 2.12. Results of ANOVA comparing mean number of M. curema per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =6.37, p<0.0023). Numbers denote number of sets...... 108
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Figure 2.13. Results of ANOVA comparing mean number of bycatch per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =33.52, p<0.0001). Numbers denote number of sets...... 109
Figure 2.14. Results of ANOVA comparing number of nets used and mean number of fish per set. Vertical bars are standard errors. Letters denote significant differences.
Numbers denote number of sets. No boats used 4 or 5 nets per set (F3,126 =33.79, p<0.0001)...... 110
Figure 2.15. Results of ANOVA comparing mean number M. cephalus per set and mesh size. Vertical bars are standard errors. Letters denote significant differences (F5,124 =24.88, p<0.0001). Numbers denote number of sets...... 111
Figure 2.16. Results of ANOVA comparing mean number of bycatch per set and net mesh size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F2,134 =3.19, p<0.0059)...... 112
Figure 2.17. Results of ANOVA comparing mean fish fork length per set and net mesh size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F2,134 =3.19, p<0.0059)...... 113
Figure 2.18. Results of ANOVA comparing mean mullet (both species) fork length per set by net mesh size. Vertical bars are standard errors. Numbers denote number of sets.
Letters denote significant differences (F5,87 =7.95, p<0.0001)...... 114
Figure 2.19. Results of ANOVA comparing mean M. cephalus fork length per set and net mesh size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F5,83 = 9.69, p<0.0001)...... 115
Figure 2.20. Results of ANOVA comparing mean number of fish per set and boat size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F6,123 =7.97, p<0.0001)...... 116
Figure 2.21. Results of ANOVA comparing mean number of fish per set and number of crew. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F4,130 =7.97, p<0.0377)...... 117
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Figure 2.22. Results of ANOVA comparing mean M. cephalus fork length per set and engine size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,121 =7.97, p<0.0001)...... 118
Figure 2.23. Results of ANOVA comparing mean M. curema fork length per set and engine size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,121 =2.23, p<0.0296)...... 119
Figure 2.24. Results of ANOVA comparing mean number of fish (all species) per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,129 =12.66, p<0.0001)...... 120
Figure 2.25. Results of ANOVA comparing mean number of mullet (both species) per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,85 =7.73, p<0.0001)...... 121
Figure 2.26. Results of ANOVA comparing mean number of M. cephalus per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,129 =2.78, p<0.0101)...... 122
Figure 2.27. Results of ANOVA comparing mean number of bycatch per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,129 =9.54, p<0.0001)...... 123
Figure 2.28. Results of ANOVA comparing mean fish fork length per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,89 =7.21, p<0.0001)...... 124
Figure 2.29. Results of ANOVA comparing mean mullet (both species) fork length per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,85 =7.73, p<0.0001)...... 125
Figure 2.30. Results of ANOVA comparing mean M. cephalus fork length per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F6,82 =5.67, p<0.0001). No M. cephalus were measured during trips with captain 8...... 126
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Figure 2.31. Results of ANOVA comparing mean number of fish per set by station. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,128 =6.84, p<0.0001)...... 127
Figure 2.32. Results of ANOVA comparing mean number of bycatch per set and station. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,128 =5.91, p<0.0001)...... 128
Figure 2.33. Results of ANOVA comparing mean total fish fork length per set and station. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,88 =4.4, p<0.0002)...... 129
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CHAPTER 1: CHARACTERIZATION OF THE STRIPED MULLET (MUGIL CEPHALUS) FISHING INDUSTRY IN SOUTHWEST FLORIDA
INTRODUCTION
The southwest region of Florida leads the nation in the catch and production of striped mullet (Mugil cephalus) and mullet roe. The following contains a background of the historical development of the striped mullet fishing industry in the state, with emphasis on Southwest Florida, as well as information on recent trends in the fishery.
Fishery data were obtained from the State of Florida’s Trip Ticket database and outlines information by county on fishing licenses, trips, and mullet landings both whole and roe.
HISTORICAL DEVELOPMENT OF FISHERY
The history of mullet fishing in Florida dates to the Paleo Indians, who resided in the southwest region of the state dating back 13,500 years (Clausen et al. 1979). The
Calusa are said to be the first to fish for mullet; notably, the tribe developed a complex society based on fishing as opposed to hunting or agriculture. Faunal remains at the coastal Wightman site on Sanibel Island indicate that >93% of the Calusa diet was fish and shellfish, <6% mammals, and <1% birds and reptiles (Widmer 1998). In contrast, inland at the Platt Island site, fish represented <20%, of the diet while mammals
2 represented >60% (Widmer 1998). Hann (1991) reported that the Calusa caught most of their fish with nets, woven mainly from palm-fiber cord but also from cabbage palm leaves, saw palmetto trunks, Spanish moss, false sisal, and the bark of cypress and willow trees. Net floats were made from cultivated gourds, and net weights were carved from mollusk shells (Hann 1991). The Calusa also used mollusk shells and bone to create spears, hooks, and throat gorges, which they used to catch other species (Edic 1996).
Their vessels—dugout canoes—were constructed from cypress and pine trees (the same as other Florida Native Americans) and were up to 15 ft. (4.57 m) long (Beale n.d. a). The shape of the boat was created by burning the center of the log and then removing the charred center with shell tools.
Life for the Calusa began to change during the 1700s amidst a prolonged war between the Spanish and English, when many were captured and sold as slaves. In 1763, the English finally took possession of the territory, and, during their 20-year reign, the
Spanish evacuated many of the Calusa to Cuba. This relationship was the foundation for creating an emerging ethnic group referred to by contemporaries as Spanish Indians
(Edic 1996).
At the same time the Calusa were being relocated to Cuba, the mullet fisheries of Cuban waters were becoming depleted. Although Cuba’s coastal ecosystems are like
Florida’s, only 13% of the island’s shoreline is estuarine, compared to 75% of the 2,200 km of coastline in Florida (Kleppel et al. 1996). Cubans began journeying north to Florida during winter months to take advantage of the still relatively untouched Gulf Coast net fishery for mullet (Beale n.d. b). They would set up seasonal fishing camps, called
3 ranchos, for four to six months, where they lived and worked among the Spanish
Indians. They would end their fishing season after roe season in January or February and return to Cuba before Lent, when demand for fish was at its peak (Beale n.d. b). They would then salt and dry their fish to preserve them. It is estimated that at that time about 30 vessels were involved, producing 1,000 tons of dried fish for export to Cuba annually (Romans 1776). Although urban consumers of Havana preferred fresh fish such as grouper, snapper and shellfish, the dried and salted mullet provided a bulk source of protein to feed the rapid influx of slaves who worked in the sugar industry on the island
(Covington 1959).
The ranchos technology advanced into the 19th century with the development of fleet boats called smacks, which were innovative for having wet wells (Edic 1996).
These watertight compartments in the hull could circulate seawater, keeping fish alive and fresh. Rather than drying and salting the fish to carry back to Cuba every few months, the smacks could sail back and forth to Cuba every week or two to sell fresh fish. The Cubans were known as the first true commercial fishers in Southwest Florida.
After the Spanish reign from 1783 to 1819, Florida officially became an American territory in 1821. Harvest of mullet throughout the state continued to thrive, and the previous ranchos were now settlements dispersed along the southwest coast from
Tampa Bay to Charlotte Harbor—melting pots of Spanish Indians, Spaniards, Cubans,
Seminoles, and African-Americans. Demand for mullet expanded throughout the southeastern U.S. as mullet remained a very inexpensive and plentiful commercial food fish. Over the next decade, the demographic of the area shifted to Anglo-Americans
4 from the South who cultivated sugar cane and other crops and sea captains from the
Northeast who were taking notice of the fishing potential in the region.
In 1832, the Legislative Council of the Territory of Florida passed a bill titled “An act for the protection of the fisheries on the coast of Florida, and to raise revenue there from to this Territory” (U.S. Congress 1848). It placed no restrictions on Florida citizens, but rather was designed to restrict harvest by foreigners and was aimed at Spanish fishers, resident or not, as well as Bahamians who were harvesting sea turtles at the time (Zacks 2013). This was the future state’s first attempt to define entitlement and regulate inshore marine space without the input of the U.S. Congress. The bill required foreign vessels to pay a $500 annual fee for fishing in American waters and they could also be subjected to random search and seizure by fisheries officials. Although this severely curtailed the fishery, the Act did not completely abolish foreign fishing, and mullet were harvested along the Gulf in dispersed locations.
Following this attempt at regulation of the mullet fishery, the U.S. government established the U.S. Fisheries Commission (USFC) in 1871, which was tasked with the procurement and research of the nation’s marine resources. In an 1877 annual report,
USFC described the mullet as the most important of the nation’s fisheries (Phillips 1884).
In 1879, the first record of mullet landings was recorded at 1.59 million kilos (3.5 million pounds) (U.S. Commission of Fisheries 1882). However, with an advancing capitalist economy, mullet harvest represented a troubled past and exemplified the low economic status of those who had relied on it for a living. Some saw mullet and commercial fishing as something that threatened Florida’s emerging image as a place for real estate,
5 recreation, and rejuvenation (Zacks 2013).
The USFC began to investigate whether other species of fishes could improve the nation’s fisheries, add value to the economy, generate wealth, and increase the social standing of fishers. The USFC turned to red snapper, a species that inhabits deeper Gulf waters, and attracted fishermen and scientists into previously unexplored marine areas.
The exploration inspired development and new, more state-of-the-art vessels and equipment, which propelled fishing in a direction more in line with the objectives of the
USFC. Red snapper represented a progressive industry for the state and thus ultimately initiated the demotion of the cultural and economic status of the mullet.
In 1884, Henry Plant extended the South Florida Railroad, which previously linked cities only on the east coast of Florida, from Kissimmee to Tampa. With the expansion of railways and steamship service, as well as the development of ice-storage and production facilities, Florida’s Gulf Coast fisheries grew. By 1889, the first white fishing families from North Carolina began settling in a location at the mouth of the
Manatee River called Hunter’s Point (Green 1985). In 1896, the growing settlement was renamed Cortez and continued to be an epicenter for mullet production along the Gulf
Coast (Green 1985). Rather than continuing the tradition of sending mullet to Cuba,
Cortez fishermen began shipping their catch northward to Tampa and Cedar Key. From there, fresh fish continued to Georgia, Alabama, and up the southern East Coast of the
U.S. By 1900, the railroad had been extended south to Punta Gorda, and the first commercial shipment was 17 box cars filled with salted mullet headed to the New York market (Zacks 2013). The first commercial ice plant in the area, the Florida Fish and Ice
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Company, was established in Punta Gorda and provided 25 tons of ice per day as well as power to the town (Edic 1996). The establishment of several new seafood dealers catapulted the area into becoming a major contributor to fisheries production and helped to integrate the southwestern area of the state with the rest of the nation.
Around the turn of the 20th century, mullet took on a broader culinary role as it began to be broiled, fried, baked, smoked, and stewed. Many considered the mullet of
Florida to be the best tasting, because they resided over sandy rather than muddy bottoms. Although the upper class preferred fresh fish, barrels of salted mullet continued to be shipped to Cuba as well as inland areas of Florida and some southern states. In 1895, commercial vessels landed nearly 2.3 million kg of red snapper worth
$155,000, while 9 million kg of mullet were landed with a value of $285,000 (Brice
1897). During this period, mullet were valued at an average of $0.01 per kg, grouper and snapper at $0.03 kg-1, and Pompano at $0.02 kg-1 (Stearns 1887). The most valuable marine product at the time was sponges, selling for an astounding $0.45 kg-1. Although mullet did not have a high monetary value per kilogram, it continued to make up a major portion of the state’s inshore fishery for many decades, and mullet roe was an important export to Asia. In 1915, mullet earned the moniker “Money Fish of Florida”
(Shell Fish Division n.d.).
As Florida continued to develop its natural resources, timber, citrus production, and phosphate mining were major stakes in Florida’s growing economy. Thus, the state saw a major land boom in the 1920s. Newly constructed hotels and golf courses targeted elite vacationers from the north, and Florida’s beaches and waterways became
7 the ultimate locations for relaxation and leisure. Though mullet remained a primary food for native Floridians, its main utility for Florida visitors was as bait to catch more desirable species. With time, the value of mullet as a commercial food fish gradually diminished relative to its use as bait for sport fishes and the value of the roe for export.
With newly established connections to northern cities such as Savannah, New
York, and Chicago, inshore fisheries in Florida continued to thrive as a contributor to the livelihoods of small coastal communities. During the 1940s, mullet harvest reached new highs because of food rationing during World War II, and many fishermen were exempted from active duty (Edic 1996). In 1947 President Truman announced a plan to help save the world’s grain supply. He suggested that citizens not eat meat on Tuesdays or poultry on Thursdays. The mullet was carefully branded as the Truman Turkey and was marketed as a protein substitute for meatless days. Mullet production reached a historic peak of 25.4 million kg during this era.
In the latter half of the 20th century, the value of coastal property soared, sport fishing flourished, and the beach-going lifestyle dominated the culture. The reputation of the mullet continued to dwindle, as other finer seafood products, such as Red
Snapper, Pompano, and shrimp, were prized. Even though mullet harvests remained high, the state viewed the species as its number one commercial fishery problem (Zacks
2013) as the value per fish remained low. Between 1952 and 1973, the price earned by fishermen ranged from $0.02 kg-1 to $0.05 kg-1 (Zacks 2013). The state was concerned about the low incomes of fishermen, minimal wholesaler profits, and minimal profits generated for the state (Cato 1976). Perpetuating the issue was the culture of the post-
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World War II period, during which the U.S. economy was steered towards mass production and consumption. Additionally, mullet was still not well known outside of the south, with greater reliance being on products such as frozen shrimp and canned crabmeat. Attempts at rebranding the fish with new styles of packaging and presentation were of little help in improving its marketability (Zacks 2013).
Over the next several decades, mullet remained the highest volume finfish harvested in the state, and so the industry continued to try to improve its marketability.
One of the biggest concerns was oxidative rancidity. Mullet has high concentrations of unsaturated fats and therefore spoils very quickly after being exposed to oxygen, even when frozen (Deng and Dennison 1976). Numerous technological studies were conducted to improve the shelf life of filleted mullet without hindering the taste, all without enormous success. In the 1960s, smoked mullet gained recognition. Popular among tourists at beachside restaurants, smoked mullet bridged the gap between a fundamental staple of the past and an item casually consumed by members of any socioeconomic class. However, smoked mullet did not elevate the status of the fresh fillet, and mullet was no longer referred to as the “money fish.” In 1962, the Florida
Board of Conservation formally changed the name from mullet, to “lisa,” the Spanish name for the fish, to bolster markets (Ingle 1962). It was legally required that the name used on a food package must match the name most commonly used by a significant proportion of the population; and because the state had a large Spanish-speaking population, the name was deemed acceptable (Futch 1966). However, the new name never caught on, and the marketing strategies had little effect on stimulating demand in
9 the North. In fact, the concept was heavily ridiculed by Florida residents, solidifying that the mullet would remain a locals-only delicacy.
In 1975, scientists from the University of Florida and the National Marine
Fisheries Service collaborated to form the Mullet Research Coordinating Committee to assess the current mullet stocks and concluded that the mullet was being underfished and underutilized (Cato 1976). One way of overcoming this issue was to export mullet roe. A few years before, trade negotiations between the U.S. and Japan for exporting
U.S. seafood products had begun. Mullet roe or karasumi (as it was known in Japan) is a culturally significant delicacy, usually served on important occasions. The National
Marine Fisheries Service (NMFS) and the Florida Department of Natural Resources (DNR) discovered that Florida mullet roe could wholesale for up to $9 kg-1 and retail for up to
$20 kg-1 (NOAA/NMFS Developments 1974). Demand, as well as price, increased immediately as the U.S. became flooded with inquiries about exporting mullet. From
1967 to 1971, fishers earned an average of $0.036 kg-1, increasing to $0.063 kg-1in 1974 as the export market grew (Thunberg et. al. 1995). By the late 1980s, prices reached an annual average of $0.17 kg-1 and $0.59 kg-1 during roe season (Thunberg et. al. 1995).
This boom caused other marine fisheries organizations to join the NMFS and DNR to continue developing mullet roe exports. By 1980, mullet flesh and roe led all seafood exports from the southeastern United States, followed by shrimp (Prochaska and Cato
1981). Taiwan and Japan had become the largest importers, followed by other Asian countries, the Middle East, and many African countries (Prochaska and Cato 1981). With the growth of the roe market, the mullet fishery’s value increased tremendously.
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Although the highly anticipated increased consumption of mullet was a success, it did pose several new concerns. The rapid increase in earning potential for fishermen created a surge of new part-time participants, often referred to as “bean-pickers”
(Lampl 1987). In 1987, there were 3,240 licensed mullet fishermen, one-third of them part-time (Adams et. al. 1990). With no entry requirements for the industry, it was easy for amateurs to purchase shallow water boats and instantly join the fishery. Because of their inexperience, they did not possess an in-depth knowledge of the local maritime laws and regulations and were not aware of the potential influence they could have on the ecosystem and the local society.
Another negative consequence of the increased market demand was excess mullet flesh. Because mullet roe was the only part of any economic and export value, fishermen tended to discard the fish once the roe was removed. Also, as female fish accumulate fat during roe season, the high risk of rancidity discouraged long-term storage. This led to huge quantities of mullet and white roe (female roe are referred to as red roe and male roe are referred to as white roe) fish carcasses being tossed overboard and washed across the Gulf coast, resulting in serious damage to the scenic beauty of the beaches and to local ecosystems.
REGULATIONS AND POLITICS OF FISHING: NET BAN
Prior to the mid-1980s, the mullet’s status along the Gulf Coast was of little concern to scientists and was not closely monitored by regulatory agencies. However,
11 the sight of all the wasted white roe fish changed the public’s perception of the business from having too little harvest, to having too much. The fishermen’s reputations were also tarnished with the perception of excess and greed. In 1985, the U.S. Fish and
Wildlife Service conducted an assessment of the mullet, which concluded that the catch per unit effort and the average size of the mullet had remained unchanged (Collins
1985).
Prior to 1983, new marine resource regulations were promulgated either by the
Department of Natural Resources or the Legislature (Marston and Nelson 1994). After criticism that this system was ineffective, the Florida Marine Fisheries Commission was created (Salz 1998). In 1998, the Florida Fish and Wildlife Conservation Commission
(FWC) was formed through a merger of three entities: the Marine Fisheries Commission, the Florida Marine Patrol, and the Florida Game and Fresh Water Fish Commission. The
Gulf States Marine Fisheries Commission (GSMFC) is the entity responsible for overseeing that the management of Florida natural resources is integrated into a regional plan. Founded in 1949, it is an organization of the five Gulf States: Florida,
Texas, Louisiana, Mississippi, and Alabama. It consists of 15 commissioners, three from each of the five states—the head of the marine resource agency, a member of the legislature, and a governor-appointed citizen with knowledge and interest in marine fisheries. The primary responsibility of the Commission is to promote sound management and use of the marine resources in the Gulf of Mexico.
The impact of commercial netting on marine resources underwent increased scrutiny in 1991, when ~6,100 Florida commercial netters landed more than 31 million
12 kg of finfish and other products valued at over $32 million (O’Hop et al. 1994). Because
M. cephalus is a bottom feeder and low on the trophic scale, it serves as an important food source for many other species such as dolphins, and many sportfish including
Spotted Seatrout (Cynoscion nebulosus), Redfish (Sciaenops ocellatus), Bluefish
(Potomatus saltatrix), Amberjack (Seriolus spp.), Mahi Mahi (Coryphaena hippurus), mackerels, Tarpon (Megalops atlanticus), and Snook (Centropomus undecimalis)
(Thompson 1963). Sport fishing and conservation groups alleged that the fishery could not sustain such pressure from the commercial industry. The recreational sector claimed that besides the overharvest of mullet, gill nets and trammel nets were killing all sea life in their path, including various species of fishes, marine mammals, turtles, and even birds. They also claimed netters were overharvesting other bycatch such as Snook,
Pompano, Redfish, and other key sport fish (Leard et al. 1995, Stern, 1999). Those concerned said that the larger mesh of gill nets “gills” the fish (i.e., the head fits through the mesh, but the broader neck and gill plate do not), thus the net holds the fish securely until the net is retrieved (Sargeant 2008). Simply stated, the nets were too effective, killing too many fish in a short amount of time. On the other hand, mullet fishermen argued that a larger mesh allows the smaller non-target fish to swim through, therefore being a more efficient method.
The FWC’s Florida Marine Research Institute, later renamed the Fish and Wildlife
Research Institute (FWRI), issued a preliminary stock assessment, reporting that
Florida’s Gulf Coast population of mullet had a Spawning Potential Ratio (SPR) of 15−
20% (Mahmoudi 1991). As a benchmark to indicate the effects of fishing pressure, a
13 more sustainable threshold is 30−35%. The GSMFC then met, agreeing that harvesting of mullet during spawning season was a legitimate concern and determining the need for an interstate Fishery Management Plan. The GSMFC proposed new regulations, with the objective of reducing the spawning season harvest period by 50% in Florida’s southwest region (Lampl 1989). After successful lobbying by wholesale and commercial fishermen, the additional rules were not implemented.
In the 1980s a group called the Florida Conservation Association (FCA), sports fishermen headed by Karl Wickstrom, the founder and publisher of Florida Sportsman
Magazine, led a campaign to give Redfish gamefish status (Marston and Nelson 1994).
Having been successful, this propelled the FCA to receive status as the foremost lobbying group for recreational fishermen in Florida. The FCA did not consider sport fishing to be equivalent to the commercial fisheries that they perceived were putting fish populations and entire marine ecosystems at risk (Smith 2006; Waters 2013). Once again, in 1991 sport fishermen intensified their efforts to convince management that inshore commercial fishing needed to be drastically reduced or eliminated, and the FCA created a group called Save our Sealife (Lollar 2014). Wickstrom then joined forces with the Coastal Conservation Association in a joint campaign called Ban the Nets (Kelley
2000, Salz 1998). They began lobbying the state legislature and made several attempts to control commercial harvest by proposing new regulations on mullet, but they were rebuffed by the Governor and Cabinet who sided with the commercial sector (Grimes
1996).
After failed attempts with the legislature, the group redirected their efforts to a
14 petition campaign to place the Ban the Nets initiative on the ballot, which would ban the use of inshore gill nets in the state. Florida is one of 18 states where a voting referendum can be used to make changes to the state constitution (Salz 1998). For success, the initiative required 430,000 voters (or 8% of the number of votes cast in the last preceding presidential election in Florida) to sign a petition filed with the Secretary of State to place the motion on the ballot (Kelley 2000). A majority vote by registered voters was required for acceptance and implementation (Florida Constitution, Article XI,
Section 3).
The Organized Fishermen of Florida, which represents commercial fishers, led the opposition by creating a group called Save our Seafood. They believed that any ban on nets would affect a traditional way of life for the commercial fishers and could have a significant financial impact on the state. They claimed that any decrease in fish populations was due to the development of the coast and habitat loss, as well as the growing sport fishing industry (Kelley 2000). The Florida Seafood Consumers and
Producers Association, which represents the many businesses that depend on the local marine resources, also opposed the ban (Kelley 2000). They argued that a ban on net fishing would deprive Florida citizens of certain species of seafood in local stores and have a significant negative impact on employment (Garant 1993).
Many scientists were skeptical of the ballot initiative campaign and hesitant to leave management decisions in the hands of the “uninformed, misinformed, and untrained public” (Barnes 1995). Brent Winner, Associate Research Scientist for the state’s Fisheries Independent Monitoring Program, maintained that although there was
15 strong popular support for the net ban, there was little scientific data to support the cause (Barnes 1995). In 1993, the GSMFC implemented an emergency ruling that limited gill nets to six hundred yards, imposed pre-spawning harvest limits, extended weekend closures from July through January, and added a ten-day closure at the end of spawning season. With the new rules in place, it was anticipated that the 35% SPR goal would be attained in 5−7 years (Mahmoudi 2000).
Convinced that commercial gill nets were responsible for several environmental problems and that the restrictions were too permissive, Wickstrom carried on with his campaign. Now with support from the Florida Wildlife Federation, the Tropical Audubon
Society, the Florida League of Anglers, and the Coalition of Fishing Clubs, his campaign was gaining momentum. Save our Sealife had more than 13,000 volunteers and raised
$1.2 million for their campaign through 11,000 donors nationwide (Lollar 2014).
Wickstrom was able to use his magazine as a forum to reach the public, with frequent articles and advertisements voicing pro net ban opinions. Additionally, pro net ban momentum gained the support of every newspaper in the state, apart from the
Tampa Tribune and Gainesville Sun, likely due to Wickstrom’s relationship with many of the sports writers (Smith 2006). Because most of the public had little knowledge of the issues surrounding the net ban outside of information from newspapers and magazines, net ban supporters had a significant advantage. Save our Sealife played on the emotions of animal lovers by using a strategic logo depicting a dolphin, sea turtle, and a fish wrapped in a gill net (Miracle 1993). They also released photographs of turtles and marine mammals, rather than fish, stranded in nets, many of which were large cargo
16 nets, not small, inshore gill nets. Some of the photographs showing large numbers of entangled fish were from abandoned gear, which was already illegal (FCA 1994). Net ban advocates portrayed the commercial fishers as immoral, greedy, and exploitative.
The net ban supporters also emphasized the foreign roe market, and Wickstrom used clever rhetoric to convey his concern by stating “roe are shipped to the Orient, where they aid in creating more Orientals instead of mullet” and “mullet are an innocent victim whose unborn eggs are being shanghaied off to the Orient” (Said 1979).
By July 1994, Save Our Sealife volunteers had collected about 540,000 signatures, well above the state’s required 429,428 (Gunter 1994). The proposed amendment was titled “Limiting Marine Net Fishing,” and was written as follows:
The marine resources of the State of Florida belong to all of the people of the
state and should be conserved and managed for the benefit of the state, its
people, and future generations. To this end the people hereby enact limitations
on marine net fishing in Florida waters to protect saltwater finfish, shellfish, and
other marine animals from unnecessary killing, overfishing and waste (Gunter
1994).
Despite having grounds to pose a legal challenge against the language of the proposed amendment, commercial fishing interests failed to do so (Barnes 1995). For approval by the Supreme Court, a proposed amendment must have a clear, unambiguous title and summary, and address a single subject (Martin 1997). However,
Martin (1997) states that approval of the title and subject is based on their technicality,
17 not constitutionality. He adds that the term “Limiting” in the title was ambiguous and misleading to voters, since the initiative was to ban and not limit the nets. It could also be argued that the amendment contained multiple subjects, as it banned several net types and protected finfish and shellfish (Salz 1998). To prevent commercial fishermen from preparing a tactical response, the Attorney General delayed releasing information about any public hearings or prevented the public from hearing about them at all (Smith
2006). Thus, the Florida Supreme Court approved the placement of the proposition on the ballot (Martin 1997). The result of the November 1994 vote was 2,876,091 to
1,135,110, or 72% in favor of the proposed amendment (Grimes 1996). The amendment went into effect July 1, 1995 and prohibited all gill nets, monofilament material, nets over 500 ft2 (45.6 m2), more than two nets on a vessel, and possession of mullet and gill nets on the same vessel (Florida Constitution, Article X, Section 16).
At the time of the vote, there were more than four million recreational anglers in
Florida, and only 16,000 commercial net fishers, demonstrating that the recreational fishery had grown significantly compared to the commercial industry over the past fifty years (Salz 1998). With such growth, economic input, and high revenue generated from license revenue, recreational fishers likely expected a greater share of the resource, although at the expense of the commercial sector (Salz 1998). Although many of the state’s fishery allocation issues are debates between recreational and commercial groups, the net ban was marketed to the voting public as an environmental and conservation concern (Grimes 1996). Commercial fishers argued that recreational groups persuaded the public in favor of the net ban by using the environment to
18 disguise their own interests (Smith and Jepson 1993). Because recreational fishermen landed nearly three-fourths of the fish population (irrespective of the type of fish), commercial fishermen had only about 25% of the fish to begin with. Banning gill nets would therefore greatly impact commercial fishermen lives and livelihoods (Seigler
2011). Not only did the net ban devalue the social value of Florida’s inshore waters as a resource for food production and an element of public good, but it also impinged on consumer rights. It reallocated the use of the resources, as well as reinforced social hierarchies. Whether it was truly intended as a conservation issue, the sheer number of recreational anglers as well as the political and financial strength of recreational fishing organizations gave them a substantial advantage in securing signatures on the petition and votes on the referendum (Salz 1998). By circumventing the normal state regulatory process, there was no opportunity for scientists to critically evaluate the biological, economic, and cultural effects of the ban. The issue had not been sufficiently evaluated by the fishery management agencies to justify a complete ban on inshore gill net fishing
(Duff and Harrison 1997). The use of a public referendum to reallocate the state’s natural resources by bypassing the agencies that manage them was unprecedented, and it ultimately deprived regulators, communities, and participants of the fishery the opportunity to be involved in the resource allocation decision.
Consequences of the Net Ban
The ban affected more than 1,500 fishing families across the state and affected
19 ways of life that had been practiced for generations (Barnes 1995). In late 1994, an
Interagency Task Force of the Net Fishing Ban was created. According to the Task Force, no evaluation was conducted before the ban to assess the potential ramifications it would have on the commercial fishers, their families, and their communities (Kelley
2000). On the other hand, an investigation was conducted to assess the possible financial effects the statute would have for the State of Florida (Kelley 2000). As a result of the referendum, the Legislature drafted a proposal to alleviate some of the financial and emotional burden for the commercial fishers, which included net buy-backs, alternative job training, and compensation for lost wages, with a total cost for the program estimated at $70−$80 million (Associated Press Report 1995). Because this program, which had promised to pay fishers a third of the value of their illegal nets, was underfunded, so the funds was depleted before all fishers could be paid (Salz 1998).
For many commercial fishers, fishing is not only a profession but a way of life.
They are very proud of their work and find other occupations unacceptable (Smith and
Jepson 1993). Although many fishers continued fishing using cast nets and other non- entangling nets, others felt these gears were too physically demanding, technically challenging, and less efficient, or they just refused to follow the new rules. For the first
18 months following the net ban implementation, the Florida Marine Patrol reported an average of one net ban related citation per day (Sargeant 1996). In February of 1996, the Florida Marine Patrol developed a program called Coastwatch, which trained citizen boat owners to find and report net ban violators (Associated Press Report 1996).
Violators who use an illegal gill entangling net face a third-degree felony, punishable by
20 up to $5,000 in fines or up to five years in jail.
Although the environmental and economic impacts of the net ban were widely discussed, the net ban had major social implications that were rarely brought to the attention of the public (Smith et al. 2003). Commercial fishers were antagonized by the pressure from recreational fishing and conservation interest groups. They believed
Floridians had been misinformed about the environmental effects of commercial fishing.
Not only did they have to suffer the financial burden of the net ban but also the public perception of their role in ecological destruction. Commercial fishing communities along the Gulf Coast that were part of Florida’s heritage for decades began to disappear. From
1992 to 2003, nearly 6,000 commercial fishermen dropped out of the fishery (Zacks
2013).
Trends in Landings
As mentioned previously, the first record of mullet landings was in 1879, when
1.6 million kg were landed (U.S. Commission of Fisheries 1883). By 1900, landings reached 14 million kg and remained at that level until 1940 (Mahmoudi 2008). Landings reached a historical peak in 1942 at 23 million kg when demand for protein increased during WW II. Mullet landings then returned to their normal annual average of 14 million kg from 1945−1966 and decreased slightly to 11 million kg until 1991
(Mahmoudi 2008). From 1992−1994, landings decreased to an average of 8 million kg.
Following the 1995 net ban, roughly 2.7 million kg of mullet were landed in 1996, a 72%
21 decrease from the 9 million kg landed in 1993 (Zacks 2013). Although average dockside prices increased, overall value declined by 50%, from $10 million to $5 million (Zacks
2013). Trends in fishing effort also mirrored this decline, decreasing 53% from the annual average of 61,449 trips during the time period 1984−1994, to 25,178 trips after the 1995 net ban (Table 1.1). Although landings had actually begun to decline prior to the net ban—the result of decreased effort in response to the emergency regulations and in anticipation of the impending ban, the major decline in landings occurred immediately after the net ban (Fig. 1.1). Due to the decrease in product value and landings, the net ban also directly affected many fish houses and wholesalers in the region. Establishments that had persisted for several decades suddenly found a drastic decline in business forcing them to close or relocate.
Mugil cephalus stocks have improved since the net ban. Prior to 1995, the SPR varied 15−20%. After 1995, the SPR increased sharply to above the 35% target level, and the most recent study determined that SPR was 42% on Florida’s east coast, 45% in northwest Florida, and 49% on the southwest coast (Mahmoudi 2014). Although this trend indicates that mullet stocks are considered healthy on both coasts of Florida, the effects of the net ban may have increased stresses on the marine ecosystem in other ways. Before the ban, mullet was the primary target species for net fishers, along with a variety of secondary bycatch such as Spanish Mackerel (Scomberomorus maculatus),
Bluefish (Pomatomus saltatrix), Spotted Seatrout (Cynoscion nebulosus) and Sheepshead
(Archosargus probatocephalus). However, post net ban many fishermen who remained in the business were more intensely targeting other species such as Stone Crab
22
(Menippe mercenaria), Blue Crab (Callinectes sapidus), and reef fishes (Smith et al.
2003). Proposed increased regulation on these species could intensify efforts on yet other species, repeating the same pattern.
The Florida Department of Environmental Protection (FDEP) listed 22 other finfish species that were impacted the most by the net ban. The total commercial landings of those species declined from 24 million kg during the period 1992−1994 to
8.2 million kg from 1996−1998 (FDEP n.d.). Average annual recreational landings of the same 22 species also decreased by 27% during the period. Concurrently, sales of resident and non-resident saltwater recreational fishing licenses increased by only 3% following the ban (Adams et al. 2000).
Some of the species most affected include the Spotted Seatrout, for which both effort and landings decreased 91%; Spanish Mackerel, landings of which dropped 56% while effort decreased 68%; Pompano, with a 61% decrease in effort and 6% decrease in landings; and Bluefish, landings of which decreased by 76% and effort by 68% (Adams et al. 2000). Other results show improvements in Spanish Mackerel stocks, which are no longer overfished in the Gulf or the Atlantic regions (Adams et al. 2000). Although a decrease in commercial landings and effort of other species such as Spotted Seatrout,
Bluefish and Pompano is certain, the full effect of the net ban is unclear as they are all highly targeted recreationally.
From 2003−2007, mullet landings averaged 3.4 million kg and accounted for 15% of commercial total finfish landings and 6% of the commercial landings total dollar value
(Mahmoudi 2008). From 2000-2007, the commercial industry accounted for 84% of the
23 total state mullet landings; the west coast of Florida accounted for 74% of those landings (Mahmoudi 2008). Also, from 1995−2007, 74% of the west coast landings came from the Tampa Bay and Charlotte Harbor areas, making the region the state’s largest contributor to overall mullet landings (Mahmoudi 2008). In 2013, total mullet landings were 20% higher than average landings of the previous five years at 6.6 million kg, the highest annual amount since the net ban. According to the most recent update of the striped mullet stock assessment, the mullet stock is proceeding optimally, with spawning to fishing ratios being at a healthy 35% (Chagaris et. al. 2014). While roe season landings have also decreased since the net ban, the proportion of roe season landings relative to the rest of the year has increased in the southwest, accounting for
64% of the annual catch. Roe season landings have remained relatively unchanged in the Northwest and East Coast regions.
CURRENT STRIPED MULLET (MUGIL CEPHALUS) FISHERY AND ROE SEASON
Management
The mullet industry remains active in the state of Florida. During the winter spawning months, fishing activity intensifies along the coast as fishermen come to the
Gulf of Mexico from all over the Southeastern U.S. to earn a share in the peak mullet fishing season. Striped Mullet (Mugil cephalus) are easily targeted (Fig. 1.2) as they congregate in large schools to head offshore to spawn. Although M. cephalus inhabit both state and federal waters in the U.S., they are most abundant in state waters and
24 therefore are managed by each state individually. The Gulf States Marine Fisheries
Commission oversees the management by each state and coordinates an overall Fishery
Management Plan (Leard et al. 1995).
The State of Florida is proactive regarding the management of M. cephalus, gathering information from both fisheries-independent and fisheries-dependent monitoring, and conducting stock assessments every 4−5 years. In 1989, M. cephalus was designated as a restricted species (RS), thereby requiring a restricted species endorsement in addition to a saltwater product license. To qualify for an RS endorsement, a fisherman must have earned either $5,000 or 25% of overall income in one of the previous three years from landings and sales of non-restricted saltwater products to a licensed Florida wholesale dealer.
Commercial harvest of mullet is prohibited beyond 3 miles (~5.5 km) from shore in both the Gulf of Mexico and Atlantic Ocean, and seaward of the Everglades National
Park boundary in Florida Bay. Size regulations include a minimum fork length of 11 inches (28 cm); undersized mullet may not exceed 10% of the total weight of all M. cephalus retained. All mullet must be landed in whole condition. Simultaneous possession of any mullet more than the recreational bag limit along with any gill net is prohibited. This rule also applies to mullet and nets that are in separate vessels or vehicles that are operating together. There are no statewide closures, but there are some additional seasonal regulations in some more residential areas along the Gulf coast.
There is no size limit for mullet caught recreationally; however, there is a 50 fish
25 per person daily bag limit between September 1st and January 1st and a 100 fish daily bag limit between February 1st and August 31st. In Pinellas County, there are more restrictive seasonal bag limits, and seasonal night closures apply in portions of Charlotte
County (FWC n.d.).
Fishing Methods
Vessels used for catching mullet typically fall into two categories, skiff or well- boat, and may be manufactured using wood, fiberglass, a combination of the two, or composite, which is a newer foam material. Skiffs are the traditional type of mullet boat and generally refer to small, flat-bottomed open boats with a pointed bow, a flat stern and an outboard motor (Fig. 1.3). A skiff’s engine and fish holding area are located mid- ship, causing it to float higher on the water and making it more conducive for cast netting.
Well boats, otherwise known as kicker boats or mullet yachts, started to appear in the 1960s. The engine is located at the bow of the boat and therefore pulls instead of pushes, allowing it to set lower in the water and making it ideal for seine netting (Fig.
1.4). A well boat is advantageous in that it uses less power and can hold more weight. It is also highly regarded for being able to go in very shallow water, sometimes as little as
76−101 cm depth.
Although more fishers use skiffs, those who fish year-round generally prefer well boats. Both boats range from 4.6−9 m long and 2.1−3 m wide, 6.6 m length being the
26 most common. The average vessel can typically hold 2,300 kg of mullet in calm weather and 1,400 kg in rough weather, while a larger 9-m boat can hold 4,500 kg of fish. The average engine is around 150 hp; however, fishermen who also fish for fast swimming fishes such as jacks prefer larger 200 hp engines, and others prefer smaller engines of 50 hp to avoid the risk of damaging their nets. Most boats also have a net table for storing nets and may have rubber mats on the deck so the leads from the nets do not hit the deck and scare the fish.
Cast nets and seine nets are the two current primary fishing methods in the region. A cast net, also known as a throw net, is a circular net with small weights distributed around its edge that, when thrown, descends like a parachute over the fish.
Historically, cast nets were simply nets with weights around the perimeter; fishermen would have to locate the net and remove the fish one at a time (Marianski 2011).
Modern cast nets contain several advances that make casting the net and retrieving the fish easier. The handline, a braided polyethylene line that floats, has a loop on one end that is held by the fisherman and is attached to the net by means of a swivel on the other end. The swivel connects the brail lines—monofilament lines that run through a plastic ring called the horn and extend all the way to the lead line. The lead line runs the perimeter of the net and contains lead weights every three inches or so.
The cast netting technique involves draping the net over the free arm so that the lead line dangles and then tossing the net by hand in a circular motion so that it spreads out on the water over the fish. The brail lines are pulled through the center of the horn to the bottom by the weighted lead line. When the net is full, the fisher uses the
27 handline to pull the brail lines and close the outer perimeter of the net around the fish.
When the full net is landed, the horn is pulled up and the net opens releasing the fish.
The size of the net used is generally based on personal preference or physical ability, but the weight of the net usually changes with conditions. Heavier chains, ranging from 3.6 to 13.6 kg, may replace leads in deeper water so that the net can sink faster. A cast net can range in size from 2.3 to 6.3 m in radius, or from horn to lead line, but the average size used is between 3 and 3.6 m. Mesh is made from monofilament and is measured knot to knot. Monofilament line is used because it cuts through the water and sinks quickly, while being very lightweight and able to dry quickly (Marianski
2011). Mesh size ranges 2−4 in (5−7.6 cm), and use depends on the size of the fish targeted. A fisherman may have 10−12 nets ready for a season and keep several on board at a time.
Seines, or haul seines, are elongated nets that hang vertically in the water column. The bottom of the net is weighted to hold it on the seabed, and the top of the net is kept on the surface by floats. Seine nets can be used from shore, such as beach seines, or deployed from boats. Typically, fishermen release one end of the net from the boat into the water and then maneuver the boat to create a large circular wall of net around the fish, preventing them from escaping. The maximum size net allowed in
Florida is 500 ft2 (45.6 m2), and while fishers don’t generally use a net smaller than that, they will use a variation of dimensions to suit their needs, such as a taller net for deeper water. Fishers also change the size of the nylon twine to suit their needs, with a lighter twine used during non-roe season and a heaver twine used during roe season when fish
28 are heavier. Most fishers choose to make their own cast and seine nets or purchase them from another local fisher, with costs ranging from $200 to $250 for a cast net and
$300−$500 for a seine net. Nets can also be purchased for a higher price at local retailers.
Although cast and seine nets are popular today, it has not always been the case.
One primitive method of catching mullet is called snatching. The method involves attaching snatch, treble, or quadruple hooks to a line on a pole about 15 ft. (4.57 m) long and suspending the hooks a few inches off the bottom (Marianksi 2011). The fisherman would jerk the pole upwards to snatch the fish with the hook. In the first half of the 20th century, another fishing method called stop netting was used. This was a cooperative initiative among crews involving one large motorized boat, called a donkey boat, that was used to pull four or five non-motorized skiffs that worked together to land the fish (Eacker 1994). Today, a similar method of fishing uses a combination of seine or hauls nets to stop the fish and cast nets to retrieve the fish. The use of this method is limited to two deployed nets per boat, regardless of net type, and can be very effective during roe season. A hoop net may also be used to assist in unloading the contents of the cast nets onto the boat (Fig. 1.5).
Historically, the most common method of catching mullet has been with gill and trammel nets ranging in size from 600−1,200 yds. (656−1097 m) in length and 2.5−4.25 in. (6.4−10.8 cm) mesh size, and large haul seines 1,000−1,200 yds. (914−1,200 m) in length (Mahmoudi 2005). Gill nets are vertical panels of netting that may work in several ways: by wedging the fish or holding the mesh around its body; gilling the fish, when the
29 mesh slips behind the opercula; or tangling the fish, when the fish is held in the mesh by its teeth, spines, or jaws without the body penetrating the mesh. In 1995, these gill entangling nets were banned in the State of Florida.
Food Fish vs. Delicacy
The human body can produce many of its own fatty acids; however, it cannot produce omega 3 (n-3) or omega 6 (n-6) fatty acids, essential for healthy brain function
(Sahari et al 2013). Although animal and vegetable oils are rich in n-6 oils, n-3 oils are only found in seafood, with mullet oils and roe being significant sources (Sahari et al.
2013). Research has shown that n-3 fatty acids can lower cholesterol, thereby reducing the risk of hypertension and cardiovascular disease (Sidhu 2003). Mugil cephalus roe also have high quantities of vitamins A, B and E, and contain other important minerals including zinc and copper (Çelik, et al. 2012).
Not only does mullet roe have many health benefits, but many cultures around the world also prize mullet roe as a delicacy. Mugil cephalus roe is prepared either as a salted product like ikura (whole salmon roe that has been removed from the sack) or salted and dried in the style of sujiko (salmon roe that remains in the sack) (Ang et al.
1999). Mullet roe is yellowish-red with a unique rubbery or chewy texture because of the high concentration of wax esters, as much as 60−70% of the extracted oil (Lu et al.
1979). The process of curing the roe involves coating it with salt for 4−5 hours, removing the salt and compressing the roe, and then air drying until its weight is reduced by 30%
30
(Ang et al. 1999). After drying it is coated with wax to prevent further desiccation and exposure to light. When roe is at optimal maturity, it can be marketed as caviar.
Although immature roe tends to be bitter, overly mature roe tends to be too soft and loses its elasticity so that it does not form a firm, full egg when brined (Bledsoe et al.
2003).
Although the consumption of mullet roe in the U.S. dates to the 1700s, it is currently a small market compared to others in the world; however, the market is growing steadily as many local chefs have discovered its advantages as a delicious, healthy, sustainable option for caviar. It is referred to as Bottarga in Italy and may be added to soups, salads, pasta dishes, as well as many Asian delicacies. In the southern
U.S., a local recipe serves it along with shrimp and grits. Although roe is the market driver for the species, the flesh of the fish is also consumed. Dining on filleted mullet is a common pastime in the Southeastern U.S.; preparations include grilling, broiling, baking, deep frying, pan frying, and most commonly, smoking. The flesh is firm, with a nutlike flavor.
Fish Processing
Following harvest, red roe are rinsed and sorted into the following size categories: under 2 oz. (57 g), 2−4 oz. (57−113 g), 4−6 oz. (113−170 g), 6−8 oz. (170−227 g), 8−10 oz. (170−283 g), and over 10 oz. (>283 g), with larger roe being more valuable than smaller roe. Sorted roe are then packed into 5 lb. (2.3 kg) boxes within 50 lb. (22.3
31 kg) master cases. The fish are stored frozen until sold, usually within a couple of months.
Although the shelf life of frozen roe is 6−12 months, it may be consumed safely for up to
24 months (Piras et al. 2014). In contrast, processed mullet can generally only be stored for 60−90 days (Cato 1976). After any type of processing, the exposed flesh tends to become unstable because of the high level of lipids present, which are susceptible to oxidative rancidity (Florida Sea Grant 1974).
Processing of Mugil cephalus into different products depends on season. During non-roe season, mullet are generally sold whole and frozen, and sometimes fresh. They are primarily used for food, and occasionally as bait, and are sold in 25 or 50 lb. (~11−23 kg) boxes. Mullet are also sold split, with the head removed and the fish split down the back and gutted, leaving the skin of the stomach intact. This technique is conducive for smoking and generally takes advantage of male mullet right before or right after roe season when fat content is highest. Female mullet do not have as much fat because their energy is spent on egg production and are generally not used for smoking. The heads from split mullet are used locally as blue crab and stone crab bait.
During roe season, processing is much more extensive. After the mullet are landed, the catch is first sorted by white roe and red roe fish, if not already sorted aboard the vessel. Although white roe mullet have a very low value during roe season, some processers will continue to purchase them to be used as bait to avoid the dilemma of fishermen discarding them overboard, as oftentimes fishermen do not sort their catch until the end of the trip when it’s too late to release the fish alive. Red roe (Fig.
1.6), as are the guts, are carefully removed from the female mullet using a knife that has
32 a ball at its tip to prevent damage. The remaining body of the mullet, referred to as the drawn portion, is sold for use primarily as food or bait. The gut fragments, including the liver and intestines, are the only discarded part of a mullet and are oftentimes sold or used as fertilizer.
Given that roe is delicate and often must be transported long distances, it should be stored under proper conditions or its composition may change due to hydrolysis and oxidation, which affect its lipid components. According to the Fish and Fishery Products
Hazards and Controls Guidance (2011), roe may be stored by freezing at an ambient temperature of -4oF (-20oC) or colder for at least seven days or freezing at an ambient temperature of -31oF (-35oC) or colder for at least 15 hours. Although storage at sub- zero temperatures extends shelf life, freezer burn can also occur. Sensory, chemical, and physical properties of roe have been shown to undergo changes during freezing: ice crystals may form, plasma membranes can rupture, and other undesirable modifications of its composition can occur (Haard and Simpson 2000).
Requirements for operating as a mullet roe processor are generally the same as those for filleting or processing any seafood. The plant must be FDA registered and have a Hazard Analysis Critical Control Point plan or otherwise a written plan defining procedures for controlling the preparation and processing of the food so that consumers do not get sick. Some international markets that import roe impose additional requirements for U.S. processors. For example, Egypt requires an inspector from the National Oceanographic and Atmospheric Administration’s Seafood Inspection
Program to perform a physical inspection of the product being shipped and to stamp
33 every box being exported (FAO 2015).
Fish Distribution
Of the 40,996,673 kg of M. cephalus landed in the U.S. between 2010 and 2015,
10,696,049 kg were exported to foreign nations, representing a significant portion (26%) of the market (Table 1.1). M. cephalus may be exported as whole frozen fish, frozen roe, or fresh roe. During the period 2010−2015, Haiti was the largest importer of whole frozen mullet from the U.S., with 2,510,013 kg, while China was the largest importer of fresh and frozen roe, with 121,165 kg and 1,125,819 kg, respectively (Table 1.2).
The price paid for mullet roe by large international wholesale buyers ranges
$13−$34 kg-1 and depends on the size of the order, as well the size of the roe, with larger roe being more valuable. The price for roe once it reaches the retail market can reach $220−$440 kg-1. The price paid to fishermen for whole M. cephalus varies, depending primarily on season. During summer months, when there is reduced demand, fishermen generally earn $1.10−$1.65 kg-1 for whole mullet. During roe season, they typically earn $0.44 kg-1 for white roe mullet and $1.10−$1.65 kg-1 and upwards of
$5.50 kg-1 for red roe. Several factors influence pricing during roe season, including the yield of roe to total fish weight, the level of roe production in other countries, farm- raised production, currency exchange rates, and overall quality.
From being called the “money fish”, the demotion of the mullet to “lisa” by the
Florida Board of Conservation has not done much to improve its marketability. Although mullet roe and female mullet are highly prized, male mullets are not and are often
34 tossed back into the ocean. Further, mullet flesh is not deemed appetizing by everyone, as many prefer the more popular pompano or red snapper. Also, the high propensity to oxidation and rancidity poses problems for long-term storage and export of mullet, forcing sellers to sell smoked fish, market only the roe, or discard the fish entirely.
Recent Trends in the Fishery
Data for the present study were obtained from the Fisheries-Dependent
Monitoring Program instated by the Florida Fish and Wildlife Research Institute (FWRI).
To identify recent trends in mullet fishery, data during the period 2010 to 2015 were used. This monitoring program comes under the State-Federal Fisheries Management
Committee (S-FFMC) (a part of the Gulf States Marine Fisheries Commission, GSMFC).
The S-FFMC was responsible for the development of a Fisheries Monitoring Program for the striped mullet (M. cephalus) after concern that the species was being overharvested following the net ban (GSMFC 1995). Using state and federal funding, the monitoring program for the striped mullet was initiated with the following objectives: a) “To analyze scientific research pertaining to this fish species to determine the
various management efforts that has been implemented over time. b) To characterize the mullet fishing industry and the changes therein. c) To identify the various organizations responsible for management efforts and
delineate their jurisdictional and management authorities.
35 d) To identify issues and troubleshoot problems within the mullet fishing industry and
ensure sustainable practices for future generations” (FWC).
The monitoring program has two facets – fisheries-dependent and fisheries- independent monitoring. The first of the two involves programs and activities that focus exclusively on fish and invertebrate species that are of economic value (like the striped mullet), while the second involves species that are important to local ecosystems and those that are fished using trawlers and other such equipment (Sarasota County
Wateratlas 2018). For fisheries-dependent monitoring, data are collected from commercial and recreational fishing activities. Commercial fishermen require a marine fisheries trip ticket that contain information including commercial licensing, fishing and unloading date and time, county where the fishing was done, type of gear used, and the quantity of fish caught (Florida Fish and Wildlife Conservation Commission 2002). The data generated by the monitoring program include the total and average landings of the fish in the different counties and regions under observation, the number of fishing licenses registered, and the number of fishing trips made by registered fishermen.
In Florida, the number of mullet fishing licenses registered between 2010 and
2015 averaged 2,808 per year with the number increasing steadily from 2010 and peaking in 2013 at 3,170, only to decline again in 2014 and 2015 (Table 1.3). The largest number of fishing licenses were issued in Manatee County (133) followed by Pinellas
(110), Charlotte (94), Lee (85) and Volusia (66). Licenses issued in these four counties alone comprised 48.75% of the total issued for this period in Florida. Sarasota County
36 exhibited one of the lowest numbers of issued licenses (17) during this period along with Union, Clay, Nassau, Marion, Seminole, and Putnam Counties. Within the four- county study area, the largest number of licenses was issued in Manatee County, followed in descending order by Lee, Charlotte and Sarasota Counties (Fig. 1.7).
Average annual number of fishing trips from 2010 to 2015 varied greatly by county, with the greatest number in Lee County (5,178), followed by Pinellas (3,113),
Charlotte (2,591), and Manatee (2,279). Within the study area, Lee County was followed by Charlotte and Manatee Counties in descending order (Fig. 1.8). There were very few fishing trips in Sarasota County over this period (Table 1.4).
Gear type (cast nets, haul seines, and others) was related to landings and the number of fishing trips during the five-year period. For instance, about 29,000 fishing trips and landings equaling 6,665 mt were made using seine nets between 2010 and
2015 (FWRI Fisheries-Dependent Monitoring). In the same period, 114,297 fishing trips and landings of 23,488 mt were made using cast nets (FWRI Fisheries-Dependent
Monitoring). Other types of gear were used in only 2,185 fishing trips and landed about
280 mt of mullet. Within the study area, the cast net was the predominant choice of gear across all counties and was used on 75% of all trips (Figure 1.9).
Mullet landings exhibited a fluctuating pattern with higher amounts acquired in
2011, 2013, and 2014 than in 2010, 2012, and 2015 (Table 1.3). Maximum landings of mullet were recorded in 2014 at 5,829.05 mt. Highest mullet landings were seen in
Manatee County (5,609.5 mt), followed closely by Lee (5,569.53 mt) (Table 1.4). Pinellas and Charlotte counties also show high mullet landings at 3,876.33 and 3,772.28 mt,
37 respectively. Together, these four counties accounted for about 62% of the total mullet landings in Florida. In all other counties, mullet landings are appreciably lower, with the highest occurring in Hillsborough (1,750.74 mt). Three of the four counties in the study area consistently produce a significant portion of the state’s mullet landings (Fig. 1.10).
Mullet roe landings between 2010 and 2015 also varied greatly across the counties, with highest red roe landings seen in Manatee (3,080.06 mt), followed almost equally by Lee and Pasco counties (1,850.74 and 1,800.05 mt, respectively) (Table 1.4).
The fourth highest landing of red roe was from Charlotte County (1,668.47 mt). Polk,
Union, Walton, Sarasota, and Lake Counties do not contribute to red roe landings in the state (Table 1.4). White roe landings mirror that of red roe, with Manatee providing the highest quantities (1,748.09 metric tons), followed by Charlotte, Lee, and Pasco (822.16,
782.09, and 750.12 mt, respectively) (Table 1.4). Union, Nassau, Monroe Walton,
Sarasota, Pinellas, and Lake Counties did not contribute to white roe landings in the state between 2010 and 2015 (Table 1.4). Within the four-county study area, Manatee
County produced the greatest roe landings (Fig. 1.11).
38
IS AQUACULTURE THE SOLUTION?
One major contributor to the global M. cephalus market is farm-raised production, and, although it does not constitute a large market in the U.S, it occurs in many regions of the world. In 2013, total production of Mugilidae was 633,351.75 mt, with 125,295.70 mt produced by aquaculture from 15 countries, corresponding to
19.8% of the total (FAO 2015). Records of mullet production date back to the 1950s in parts of Southeast Asia and Italy. A large increase in production began in the 1990s and production peaked in 2007 at 246,537.11 mt (Crosetti and Blaber 2016). More recently, production averaged 120,631−136,050 metric tons from 2011 to 2013 (FAO 2015).
Egypt consistently produces the greatest amount of the world’s cultured mullet, accounting for 116,151 tons (84%) in 2013 (FAO 2015). Most of the remaining cultured mullet comes from the Mediterranean, Korea, Taiwan, Italy, Saudi Arabia, and Japan
(FAO 2015). Mullet aquaculture is relatively unexplored in the U.S., except in Hawaii; however, that practice is disappearing, as in 2000 there were only two active ponds, producing less than 500 kg (Hawaii Division of Aquatic Resources 2004).
Mullet have several biological characteristics that make them an attractive fish for cultivation (Crosetti and Blaber 2016). Because mullet is a euryhaline species, it can be cultured at different salinities from fresh water to a high salinity. This characteristic also allows it to be polycultured with other marine and freshwater species such as carp, tilapia, and milkfish. Because mullet are low on the trophic scale as consumers, they can be inexpensively and efficiently fed a wide variety of foods, ranging from micro-
39 organisms to insect larvae (Crosetti and Blaber 2016).
Even though mullet are a hardy fish, large-scale production has not attained the levels of other marine species. One limiting factor is that mullet do not spawn spontaneously in captivity without being induced with hormones. Female mullet in captivity proceed to the secondary or tertiary stage of yolk development, but the process stalls without the natural environmental stimulus of migration offshore (Crosetti and Blaber 2016). This limitation prevents the harvest of the most valuable part of the fish, the roe, and creates a dependency on the continuous collection of fry from the wild for production. The availability of wild fry is not always stable or sufficient for stocking, and their harvest is illegal in some countries. In those countries where wild fry are collected for culture, social problems may develop because of the competition among fish farmers and fishermen. Despite many experimental trials to improve spawning in captivity, mullet culture has not achieved commercial scale given the cost-benefit ratio, with the cost of hormones as a major factor. In Egypt, for example, 10 g fingerlings produced in hatcheries cost $0.30 USD each, whereas wild 10 g fingerlings sell for
$0.10−0.12 each; the total cost of producing 1 kg of mullet in an aquaculture facility is
$0.75−1.00 (FAO 2015).
Cultured mullet potentially could be a sustainable option given the following considerations: negative effects of collecting wild fry are avoided; aquaculture systems are improved to decrease cost and increase survival of fry; management is improved to reduce the negative effects of intensification; artisanal fishing grounds and stocks are protected; and those involved follow the FAO Code of Conduct for Responsible Fisheries
40 in order to assure that mullet culture is conducted sustainably and responsibly (FAO
2015).
CONSERVATION CONCERNS
As a key component of the Florida Gulf Coast inshore ecosystem and Florida’s economy, M. cephalus continues to be monitored on a regular basis. As mentioned previously, current (2014) stock levels of M. cephalus are considered healthy in all parts of the state. Mugil cephalus is listed as a “best choice” option by Seafood Watch, and all the sustainability criteria in the Table of Ranks including vulnerability, status of stocks, nature of bycatch, habitat effects, and management effectiveness are listed as of low concern (Mahoney-Stevens 2004).
Although Mullet stocks are currently healthy, environmental, political, and social concerns regarding the species remain. With the deep cultural history surrounding mullet fishing, as well as being a common property resource of the marine environment, such struggles are no surprise. Economists refer to the consequent problem associated with this phenomenon as the Tragedy of the Commons, a model based on the observation that where natural resources are common goods, but exploited by individuals in competition with each other, the industry will degrade and eventually destroy that resource. Human nature is to maximize immediate profits, and, because people have no individual incentive to conserve the resource, any resource they fail to extract will only be taken by others. However, in the case of commercial mullet fishers
41 along the Florida Gulf Coast, this tenet may not hold. In a community survey of Cortez,
Florida, income was rarely mentioned as one of the incentives that kept Cortez fishers on the water; rather the opportunity to work outdoors, as well as the thrill of the water and the freedom of working independently were cited (Cortez Village Historical Society
1985). Many commercial fishers live to fish, rather than fish to live, and believe it is a calling, not a job (Eacker 1994).
Whenever a new environmental policy is being considered, the precautionary principle should be applied, because the resilience of ecosystems and the effects of human activities can be hard to forecast and difficult to distinguish from natural variability (Cochrane and Garcia 2009). The precautionary principle means that actions or policies that entail risks should not be undertaken without scientific evidence that the risks are acceptable. Ultimately, commercial fishermen were highly affected both emotionally and financially by the 1995 net ban, and because the law was enacted via public voting referendum, proper implementation of the precautionary approach was not conducted. Many other regulatory conservation methods could have been considered besides banning gill nets altogether. Some of these potential regulations include modifying net and mesh sizes during seasons; regulating harvest times and areas; limiting time at sea; limiting the potential catch through daily limits or individual yearly quotas; limiting the number of crew; and limiting the number of entries, especially out-of-state licenses.
A number of environmental concerns threaten the future of mullet populations along the Florida Gulf Coast; habitat loss due to human activity is a priority issue. With a
42 rising population and more development, dredge and fill operations for waterfront home sites, along with seawall construction are causing direct habitat loss by destroying mangrove shoreline and mullet feeding areas in seagrass beds. Habitats are also threated by the cumulative impacts of docks and boats, invasion of non-native species, and poor water quality due to runoff from polluted storm water, wastewater, and atmospheric deposition. Runoff may carry a large load of suspended solids such as soil and silt, which increase the turbidity of the water and decrease light needed for photosynthesis by seagrass. Excess nitrogen and phosphorus from runoff may also contribute to blooms of red tide (Karenia brevis), a dinoflagellate that occurs naturally but, under the right conditions of excess nutrient loading, can occur in high concentrations as a harmful algal bloom. Karenia brevis releases toxins that paralyze the nervous systems of marine life including mullet and causes large fish kills. Mullet are susceptible to the toxin by way of gills or respiration, oral or gastrointestinally, or through dermal pathways (Woofter et al. 2005). After exposure, mullet quickly accumulate brevetoxins in their blood and retain detectable amounts for several days
(Woofter et al. 2005). Not only are the toxins harmful to mullet, but also to those that ingest it, including predators in the wild as well as humans.
A changing climate also has the potential to completely alter the structure and function of the region’s estuaries. The effects of climate change include changes in nutrient fluxes, alterations to hydrologic cycles, rising sea levels, rising water temperatures, and relocation of spawning and feeding habitats.
43
The status of mullet stocks in the future will depend on markets, fishing effort and landings, as well as changes in the environment that can cause variability in recruitment and other aspects of the population. Because the stock has been increasing since the net ban, fishing mortality rates should be either stable or decreasing if the recovery continues on its current trajectory. According to Mahmoudi (2014), future assessments should include age data from the fishery to obtain accurate estimates of gear selectivity. Fishery-independent sampling will be required to provide improved estimates of biological and population attributes needed for inclusion in and calibration of stock assessment models (Mahmoudi 2014). Given the importance of mullet in energy flows in estuarine and coastal ecosystems and their trophic status as secondary consumers, models should include predator-prey interactions, as well as bottom-up processes such as those involving nutrients, eutrophication, and climate change. Rates of predation on mullet (a key factor for a forage species) and overall natural mortality rates (essential for population models) could be estimated using ecosystem-based or multispecies modeling techniques (Mahmoudi 2014). Although mullet has historically been considered a trash fish, it has been proven to be extremely valuable to the environment, economy, and culture of the state of Florida.
44
TABLES
Table 1.1 Florida Commercial Mullet Landings 1984-2015.
Estimated Year Kilograms Trips Average Price $ Value $ 1984 2,125,315.67 8,943 0.51 2,378,674 1985 9,105,107.51 47,729 0.28 5,712,187 1986 10,336,062.86 57,790 0.33 7,535,663 1987 10,434,885.21 58,556 0.35 8,019,398 1988 10,715,316.88 62,925 0.41 9,612,576 1989 12,199,503.32 67,341 0.48 12,911,777 1990 11,801,591.23 71,001 0.49 12,750,572 1991 10,067,416.88 62,494 0.49 10,896,653 1992 9,359,173.22 61,380 0.56 11,579,086 1993 9,275,815.64 55,441 0.59 12,094,741 1994 6,805,255.85 47,405 0.74 11,070,856 1995 2,580,288.77 24,618 0.87 4,926,244 1996 2,567,255.25 25,521 0.9 5,119,028 1997 3,895,600.51 31,254 0.75 6,428,401 1998 4,120,244.85 30,034 0.6 5,430,732 1999 4,383,385.12 29,597 0.76 7,327,627 2000 3,889,343.65 27,742 0.65 5,578,290 2001 4,631,954.65 26,256 0.65 6,627,294 2002 4,099,703.92 25,471 0.73 6,574,794 2003 3,566,834.94 24,932 0.69 5,432,796 2004 3,462,127.68 23,805 0.71 5,446,226 2005 3,018,972.02 21,042 0.74 4,897,770 2006 4,132,827.95 24,030 0.79 7,238,741 2007 3,096,309.97 20,367 0.63 4,281,790 2008 3,802,663.06 22,773 0.57 4,778,763 2009 4,691,388.40 23,848 0.54 5,555,391 2010 3,840,530.31 21,564 0.57 4,818,273
45
2011 5,760,836.74 25,200 0.75 9,463,034 2012 4,359,049.89 23,844 0.72 6,893,857 2013 5,548,467.06 28,057 1 12,278,316 2014 5,989,832.40 25,759 0.78 10,269,714 2015 4,523,116.07 24,226 0.7 7,021,755
46
Table 1.2. Total Mugil cephalus imported by various countries, 2010−2015.
Nation Whole Frozen (kg) Fresh Roe (kg) Frozen Roe (kg) China 920,036 121,165 1,125,819 Colombia 1,832,495 0 86,863 Dominican Republic 1,502,407 0 5465 Egypt 1,115,269 0 55,326 Haiti 2,510,013 0 153,492 Italy 17,661 18,398 325,762 Belgium 0 0 56,223 France 13,000 0 87,637 Spain 22,771 0 215,821 Japan 0 4351 3597 Vietnam 17,538 19,198 0 Netherlands 465,742 0 0
47
Table 1.3. Statewide total M. cephalus licenses and landings by year (2010–2015). (Data courtesy Steve Brown FWRI Fishery Dependent Monitoring).
Categories 2010 2011 2012 2013 2014 2015 Registered Licenses 2,287 2,682 2,800 3,170 3,117 2,794 Landings (metric 3,275.75 5,689.62 4,212.00 5,424.27 5,829.05 4,213.89 tons)
48
Table 1.4 County-wide distribution of total red and white roe landings, total M. cephalus landings, average number of M. cephalus fishing trips, and average number of registered licenses with mullet landings per (2010–2015). (Data courtesy Steve Brown FWRI Fisheries Dependent Monitoring).
Red Roe White Roe Landings Trips Licenses County (kg) (kg) (kg) (avg) (avg) Bay 21,610.08 16,952.82 23,3132.67 529 16 Brevard 66,072.58 23,540.80 323,336.71 794 27 Broward 141.82 75.91 1,484.45 5 2 Charlotte 1,671,974.16 823,891.36 3,780,210.79 2,591 94 Citrus 12,832.73 7,861.82 574,387.52 691 15 Collier 48.18 0.00 667,283.05 283 28 Dixie 266,892.36 225,756.27 195,465.52 328 9 Duval 14,195.00 9,116.45 679,390.86 294 31 Escambia 481,607.00 168,350.40 918,922.87 943 21 Franklin 35,376.89 17,505.27 787,681.01 717 42 Gulf 176,994.33 159,612.92 1,180,476.45 607 15 Hernando 424,380.91 300,016.36 484,866.64 223 15 Hillsborough 279,956.82 100,620.95 1,754,421.80 1,567 51 Indian River 883,475.95 207,017.20 236,166.14 530 23 Jefferson 68,868.64 31,877.05 6,925.00 7 2 Lake 2,156.82 1,433.64 1,252.73 1 2 Lee 0.00 0.00 5,581,240.49 5,178 85 Levy 1,854,625.77 783,738.67 19,922.10 47 4 Manatee 1,415.45 6,014.09 5,621,294.77 2,279 133 Marion 3,086,534.75 1,751,760.70 240,596.29 4 1 Martin 0.00 0.00 2,822.78 729 26 Miami-Dade 100,100.91 31,805.00 371,224.64 8 2 Monroe 224.09 109.09 251,508.67 3 2 Nassau 38.18 0.00 114,118.12 1 1 Okaloosa 3.64 0.00 3,884,482.49 233 8 Palm Beach 7,258.36 4,033.18 2,209.09 787 42
49
Pasco 68,062.13 38,438.84 316,691.56 73 11 Pinellas 56,759.61 33,793.35 179,240.87 3,113 110 Polk 1,803,836.54 751,692.90 1,691.82 17 3 Putnam 0.00 295.45 64,500.08 1 1 Santa Rosa 38.64 0.00 377,523.90 489 21 Sarasota 56,697.05 20,482.95 102,437.15 91 17 Seminole 108,733.06 43,094.18 966,192.97 12 1 St Johns 0.00 0.00 500,123.46 70 9 St Lucie 15,346.14 8,451.97 42,923.32 867 36 Taylor 119,387.41 61,099.09 643.12 303 5 Union 8,903.64 1,467.73 3,796.82 0 1 Volusia 0.00 0.00 22.02 676 66 Wakulla 675,985.77 167,541.00 27,147.14 516 18 Walton 36,450.91 34,973.41 22.73 45 5
50
FIGURES
Peak landings, followed by decline in response to decreasing effort in anticipation of net ban 14,000,000 Net ban implemented 12,000,000
10,000,000
8,000,000
6,000,000 Landings (kg) Landings 4,000,000
2,000,000
0
Year
Figure 1.1 Florida statewide M. cephalus landings by year 1984-2015.
51
Figure 1.2 Mullet fishermen during roe season in Big Pass, Sarasota.
Figure 1.3 Traditional mullet skiff (photo courtesy of Steven Ball).
52
Figure 1.4 Traditional well boat (photo courtesy of Kracker Built Boat Works).
Figure 1.5 Use of hoop net during roe season (photo courtesy of Kenny Jenkins).
53
Figure 1.6 Harvested red roe at AP Bell Seafood Co.
600
500
400
300
200 Number oflicenses Number 100
0 2010 2011 2012 2013 2014 2015
County Charlotte Lee Manatee Sarasota
Figure 1.7. Number of registered licenses in study area by county and year 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring).
54
6,000
5,000
4,000
3,000
2,000 Number of fishing trips offishing Number 1,000
0 2010 2011 2012 2013 2014 2015
County Charlotte Lee Manatee Sarasota
Figure 1.8. Total number of M. cephalus fishing trips in study area by county and year 2010-2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring).
55
16,000
14,000
12,000
10,000
8,000
6,000
4,000
Number of fishing trips offishing Number 2,000
0 Charlotte Lee Manatee Sarasota County
Cast Net Seine Net Other
Figure 1.9. Number of M. cephalus fishing trips in study area by gear and county 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring).
56
1,800,000
1,600,000
1,400,000
1,200,000
1,000,000
800,000
Landings (kg) Landings 600,000
400,000
200,000
0 2010 2011 2012 2013 2014 2015
County Charlotte Lee Manatee Sarasota
Figure 1.10. Total M. cephalus landings in study area by county and year 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring).
57
3,500,000
3,000,000
2,500,000
2,000,000
1,500,000 Landings (kg) Landings 1,000,000
500,000
0 Charlotte Lee Manatee Sarasota County
Red Roe White Roe
Figure 1.11. Total red and white roe M. cephalus landings in study area by county 2010−2015 (data courtesy Steve Brown FWRI Fisheries Dependent Monitoring).
58
59
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Mahoney-Stevens, M. 2004. Striped Mullet: Southeast Atlantic and Gulf of Mexico Regions Final Report. Monterey Bay Aquarium.
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CHAPTER 2: SEASONAL VARIATION OF THE COMMERCIAL STRIPED MULLET (MUGIL CEPHALUS) FISHERY IN SARASOTA BAY AND CHARLOTTE HARBOR: THE EFFECTS OF ENVIRONMENTAL VARIABILITY AND FISHERY-DEPENDENT FACTORS ON CATCH RATES
INTRODUCTION
Mugil cephalus is an important commercial fisheries species in the state of
Florida. From 2004 to 2013, 85% of statewide landings of striped mullet came from the
Gulf Coast, with 80% of those landings from Southwest Florida near Tampa Bay and
Charlotte Harbor (Mahmoudi 2014). During this same time period, 68% of west coast
landings were made during spawning season (Mahmoudi 2014). Spawning season, when
the eggs of female mullet are harvested and sold as a delicacy for high prices in several
parts of the world, provides a lucrative opportunity for fishermen. Fishers target Striped
Mullet as they congregate in large schools and head offshore to spawn.
Because M. cephalus spends most its life cycle in inshore waters, the fishery is
managed by the State of Florida and has undergone many regulatory changes over the
years. Following an increase in the exportation of mullet roe in the early 1990s, the
status of M. cephalus was reported as overfished (Mahmoudi 2014). Because mullet are
low on the trophic scale, they serve as an important food source for many species,
including some sport fishes. This raised the attention of many recreational fishers and
environmental agencies. After an ongoing dispute between commercial and recreational
anglers, the most popular commercial mullet fishing method, gill netting, was banned in
1995 by means of a public voting referendum. The net ban marked a significant moment
in the history of mullet fishing in the state. Following the ban, factors such as changes in
69 environmental and ecological conditions and their effect on fishing mortality and
Spawning Potential Ratio have not been fully evaluated. In order to better understand the fishery and move towards an ecosystem-based approach to management, it is important to take into consideration as much information as possible, some of which may only be available through onboard observation. The federal observer program, which provides professionally trained biologists onboard commercial fishing and processing vessels, has been a vital component for collecting pertinent fisheries information used to support science, conservation, and management activities.
Observers directly gather data on catch composition, protected species interactions, bycatch information and gear configuration, and they monitor compliance with fishing and safety regulations (NOAA 2018). While this program has been actively collecting data from vessels fishing in federal waters for several decades, little work has been done to collect similar information onboard commercial vessels fishing inshore. The approach of this study was an attempt to see if it was feasible to collect quality data onboard small commercial vessels, fishing the inshore state waters of Florida.
The goal of this project was to collect relevant data useful for fisheries management, including comprehensive onboard observations for characterizing the spatial and temporal patterns in fishing activities and effort in the mullet fishery. This project collected data to qualitatively and quantitatively describe a typical mullet fishing trip on the west coast of Florida: number of hours fished, number of crew, number of throws and sets, size of boat, and gear information. Catch composition, including the total number of fish, number of M. cephalus and M. curema, number of bycatch,
70 average fish size, and sex were recorded, and the influence of various environmental factors, such as temperature, salinity, and dissolved oxygen on catch was analyzed.
Because the project supports overall ecosystem management, information about relevant habitat, such as bottom type, depth, and distance to shore, was also recorded.
Finally, the project examines regional differences between Sarasota Bay and Charlotte
Harbor.
Taxonomy
The Striped Mullet Mugil cephalus (Linnaeus 1758) is known in various locations as Black Mullet, Common Mullet, Flathead Mullet, Gray Mullet, and Sea Mullet. Mugil cephalus is an Actinopterygian teleost (ray-finned fishes, a class of bony fishes), order
Mugiliformes, family Mugilidae (Nelson 2016). Within the family, there are 20 genera and 70 species, M. cephalus being the most widespread (Eschmeyer and Fricke 2011).
Nine species are found in the west central Atlantic (Ditty and Shaw 1996). On the Florida
Gulf Coast, M. cephalus is the most abundant mullet, followed by M. curema and M. gyrans.
Mugil cephalus can be distinguished from the similar M. curema by having eight anal fin rays rather than nine, as well as 42 versus 38 scales in the lateral series and 14 versus 12 in the transverse series (Jacot 1920). In contrast to M. cephalus, M. curema has scales that extend onto its dorsal and anal fins.
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Biogeography
Mugil cephalus is a cosmopolitan species, found in temperate, subtropical, and tropical coastal waters worldwide, ranging between latitudes 42° N and 42° S
(Thompson 1966). These latitudes correspond with minimum water temperatures of
16°−18°C (Smith and Deguara 2002). Mugil cephalus has several eurytopic characteristics that allow it to maintain such a wide distribution. It is a euryhaline species, able to live in salinities ranging from completely fresh (0 ppt) to hypersaline
(75−80 ppt) (Cardona 2006, Whitfield et al. 2006). However, such wide salinity ranges can only be tolerated after they reach 4−7 cm in length. (Bester 2004). Evidence suggests that the gill filament epithelium undergoes ultrastructural changes, with the chloride cells adapting rapidly to salinity changes (Whitfield et al. 2012, Hossler 1980).
Despite a wide salinity tolerance, optimal conditions for maximum growth are oligohaline and mesohaline waters (Cardona 2006). Mugil cephalus can also survive in waters with a wide range of dissolved oxygen levels, and they are able to switch to anaerobic metabolism while in hypoxic water (Hoese 1985; Vagner et al. 2008). In addition, in low oxygen conditions they use aquatic surface respiration to supplement their oxygen levels by gulping air into their upper pharyngeal chamber (Hoese 1985,
Shingles et al. 2005). Evidence shows that jumping frequencies increase with lower dissolved oxygen concentration and that the pharyngobranchial organ can hold gas
(Hoese 1985).
Striped Mullet represents a rare example of a coastal marine species that is distributed worldwide. The species likely originated in the Indo-West Pacific, with an
72 eventual circumglobal distribution aided by dispersal at various life-history phases, i.e., by larval drift or adult migration (Livi et al. 2011). Colonization of the Atlantic Ocean and
Gulf Coast may have occurred before the formation of the Isthmus of Panama via larval dispersal around the Cape of Good Hope (Livi et al. 2011). Although populations throughout the world are genetically distinct, they are morphologically similar (Rossi et al. 1998). Aspects of population dynamics, such as reproduction, diet, growth rate, and sex ratio may also vary among populations (Lee et al. 1996).
Habitat and Movement
Mugil cephalus are found in shallow, inshore marine waters over a variety of bottom types, including mud, sand, silt, sea grass, shell, oyster, and rocky bottoms
(Bester 2004). Although they frequent a variety of habitats, they prefer fine sediments, such as mud and sand, where they feed on decaying organic detritus (Mahmoudi 2005).
In some parts of the world, such as Australia, South Africa, India and Israel, they can be found in fresh water and are therefore referred to as catadromous—species that spawn in salt water and reside in fresh water (Thompson 1963). Generally, they reside in bays and estuaries and do not move or migrate, except for traveling offshore to spawn during the winter months (October−January in Southwest Florida, Broadhead and Mefford
1956). Mugil cephalus are schooling fish, with the size of the school varying seasonally in relation to feeding and reproduction. Schools are smaller during feeding and post- spawning and larger during the spawning phase and migration (Thompson 1955).
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Feeding
The feeding ecology of M. cephalus has received some attention because it is one of the very few larger marine fishes that feeds directly on primary producers and detritus as adults, making it an important forage fish and major component in the energy flow in an estuary (Collins 1985, Mahmoudi 2005). Adult Striped Mullet bottom- feed on detritus (iliophagy) or graze on epiphytic and filamentous algae (herbivory)
(Thompson 1966). In contrast, mullet larvae feed primarily on zooplankton (Smith and
Deguara 2002). After recruitment to estuaries, juveniles 20−55 mm in length transition from planktonic carnivory to omnivory and finally to an adult diet (De Silva and
Wijeyaratne 1977). Mullet feed diurnally, with little to no activity at night; maximum feeding intensity occurs between 11:00 and 18:00, with feeding habits differing spatially and temporally (Collins 1981, De Silva and Wijeyaratne 1977). Mullet from freshwater sites consume more plant material than mullet from estuarine sites (Collins 1981). Their gizzards aid digestion by grinding up difficult to digest food items (Thompson 1963).
Striped Mullet are preyed upon principally by larger fishes, large birds such as pelicans, marine mammals such as dolphins, and sharks and sawfish (Bester 2004).
Age and Growth
Larval M. cephalus average ~2.65 mm in total length (TL) at hatching (Finucane et al. 1978). After day one, TL increases to 3.36 mm (Mahmoudi 2005). They begin feeding on day five, and by day 25 they are ~10.9 mm TL (Mahmoudi 2005). During the
74 pre-juvenile stage (11−52 mm TL), growth is temperature dependent, with the duration of this stage varying from 30−90 days (Anderson 1958, Mahmoudi 2005). Juveniles range in size from 44 to 200 mm standard length (SL) and reach 185 mm SL by the end of the first year (Anderson 1958, Mahmoudi 2005). Adults typically grow 38−64 mm per year, mostly during the warmer spring and summer months (Broadhead 1956, Cech and
Wohlschlag 1975). The lifespan of Striped Mullet is 9−13 years, with females living slightly longer than males (Mahmoudi 1991).
Prior to sexual maturity, mullet spend most of their energy on lengthwise growth and the development of sensory organs to avoid predation (Gallardo-Cabello et al.
2012). In these early stages, growth rate is higher in females than in males; but once gonadal maturity is reached, male growth rates increase (Gallardo-Cabello et al. 2012).
After sexual maturation, energy is reallocated to reproduction and storing fatty acids for weight gain (Gallardo-Cabello et al. 2012). Mugil cephalus undergo their first spawning between ages 2 and 6, corresponding to total lengths of 260−450 mm (females) and
250-440 mm (males) (Gallardo-Cabello et al. 2012, Thompson 1963). However,
Thompson et al. (1991) observed Mugil cephalus as small as 220/240 cm (male/female) at age two offshore in the Gulf of Mexico, suggesting the possibility that they may mature even younger. Variation in age and size at maturity may be due to environmental conditions, with warmer waters corresponding to faster growth and earlier reproduction (Anderson 1958). Mahmoudi (2005) also reports that mullet in
Southwest Florida reach maturity between 2−3 years and ~290−380 mm fork length.
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Reproduction
Spawning migration patterns vary depending on geographic location, but spawning always occurs offshore. Migration distances as long as 400 km have been reported along African coasts and up to 740 km along coastal Australia and China
(Bernardon and Vall 2004, Whitfield et al. 2012). However, spawning in the Gulf of
Mexico occurs in surface waters 64−80 km offshore (Arnold and Thompson 1958). In locations experiencing high freshwater runoff, such as in New South Wales, Australia, mullet may spawn farther offshore than in other regions of the world (Smith and
Deguara 2002).
During the months of October through January, strong cold fronts accompanied by falling barometric pressure and northwesterly winds along the Gulf Coast of Florida have been associated with mullet congregating in large schools to move offshore to spawn (Mahmoudi 1993). Peak spawning season is usually December; however, the exact timing of reproduction may vary due to environmental factors. Walsh et al. (1991) determined that the optimum yield of normal larvae occurs at a water temperature of
25°C and a salinity of 36 ppt; however, Nordlie et al. (1982) found that larvae tolerate salinities of 20−39 ppt under experimental conditions. Ripe gonads of estuarine fish are reabsorbed when denied access to the sea, verifying that a marine environment is a requirement for spawning (Wallace 1975).
Actual spawning observations have been rare, but one sighting by Arnold and
Thompson (1958) reported that males appeared to congregate around individual females, then leave the school, swimming in an erratic manner near the surface.
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Occasionally, one or more males would nudge the abdomen of a female and cease to swim momentarily (Arnold and Thompson 1958). A female M. cephalus can produce anywhere from 45,000 to 4 million eggs averaging 840−950 µm in diameter (Greely et al. 1987). Eggs are fertilized externally, and hatching occurs approximately 22−30 hours after fertilization in Mediterranean waters (El-Gharabawy and Assem 2006). In northeast Florida, females produce one clutch of eggs per year, although they do not release all of the eggs at one time (Greely et al. 1987). Because the female body cavity does not have sufficient volume to host a full clutch of hydrated eggs at one time, batches of oocytes may be hydrated on successive nights until the supply becomes exhausted (Smith and Deguara 2002). Evidence of fish with partially spent eggs further supports this notion (Stenger 1959).
Initially, the yellow-pigmented unfertilized eggs are positively buoyant but become negatively buoyant after fertilization (Thompson 1963). Larvae begin to sink within the first 10 days after hatching yet continue to maintain a high level of phototaxis
(Liao 1981). Schooling commences while in the pelagic phase at the age of 2−3 months
(11−40 mm length) as young fish begin to recruit to estuaries (Thomson 1955).
Complete recruitment to estuaries continues through ages 4−6 months; however, some juveniles may be delayed due to larval drift (Anderson 1958, Thompson 1963).
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MATERIALS & METHODS
Study Area
Sarasota Bay
Sarasota Bay is an estuary located on the west coast of Florida (Fig. 2.1). The bay is approximately 90 km long, with an average depth of 2 m, and the watershed occupies
418 km2 within Manatee and Sarasota Counties (SWFWMD 1999). Sarasota Bay is made up of many smaller bays including Palma Sola Bay, Sarasota Bay proper, Roberts Bay,
Little Sarasota Bay, and Blackburn Bay. Sarasota Bay separates the mainland from several barrier islands and is connected by three passes to the Gulf of Mexico: Big Pass,
New Pass, and Longboat Pass. The area consists of a diverse range of estuarine habitats including mangroves, salt marshes, salt flats, seagrass beds, sandy tidal flats, oyster bars, and hard bottom.
Charlotte Harbor Estuary
Charlotte Harbor is a 700 km2 estuary that stretches across Charlotte and Lee
Counties (SWFWMD 1999) (Fig. 2.1). Average depth is 2.1 m, with the northern portion being considerably deeper than the southern (McPherson et al. 1996). The shoreline consists mostly of mangroves, but saltmarshes are also present in the intertidal river regions (McPherson et al. 1996). Charlotte Harbor is made up of many smaller bays and creeks including Lemon and San Carlos Bays; Godfrey, Rock, Oyster, Buck, Coral, and
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Island Creeks; Placida Harbor, Charlotte Harbor Proper; Gasparilla and Pine Island
Sounds; Sanibel River; Matlacha Pass; and Gator Slough Canal. The estuary connects to the Gulf of Mexico through Boca Grande Pass between Gasparilla Island and Lacosta
Island. Charlotte Harbor has greater freshwater inflow than Sarasota Bay because it collects water from three significant rivers, the Peace, Myakka, and Caloosahatchee
(Tomasko et al. 2005). Much of Charlotte Harbor is designated as preserve and is publicly owned (FDEP 2018). However, with rapid increase in growth and development, as well as an increase in agricultural and industrial wastes, the Harbor is increasingly threatened.
The climate in the study area is subtropical, with warm, rainy summers, and mild, dry winters. Temperatures average 27 °C during the summer and 16 °C in winter. Mean annual rainfall ranges between 136 and 144 cm yr-1, with most of the rainfall occurring between June and September (SWFWMD 1999).
Fishers and Vessels
During the period September 2012 to January 2014, 36 sampling trips (Table 2.1) were completed, defined as from the time a vessel leaves the port to the time it returns and lands its catch. Eight fishers residing in the study area were selected and agreed to participate; each was assigned a number, 1−8, to maintain anonymity. Fishers were selected according to the following attributes: frequent mullet fishers; location of fishing effort; cast netting as the primary fishing method; and willingness to participate
79 in the study. The study was conducted through the Florida Fish and Wildlife Research
Institute, in St. Petersburg, Florida. On each sampling day the departure location was recorded, as well as the following vessel information: length (ft.), motor size
(horsepower), type of gear and number of nets onboard, gear mesh size, and number of crew.
Environmental Factors
A number of environmental factors were also recorded during each fishing trip.
Moon phase was recorded as new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, or waning crescent. The presence of cold fronts was also noted. Immediately upon deployment of a net at each set, several environmental variables were recorded (a set was defined as a series of throws at each new location reached by motor; 137 sets were completed during the sampling period).
A GPS unit was used to record latitude and longitude at each location. Tide was recorded as high slack, ebb, low slack, or flood. Cloud cover was reported as a percentage. Depth was visually estimated (m) and bottom type was recorded as sand, mud, oyster, or seagrass. Distance from shore (m) was also visually estimated and shore type was recorded as mangrove, seawall, or beach. A handheld anemometer was used to measure barometric pressure (mm Hg), air temperature (°C), wind speed (mph), and direction. Salinity (ppt), sea surface temperature (°C), and dissolved oxygen (mg L-1) were measured using a portable YSI multiparameter sonde at a depth of 0.2 m.
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Fish Sampling
Each fish brought to the vessel was recorded by throw and set, and labeled as target (M. cephalus), M. curema, or bycatch. Fork length (FL) was recorded to the nearest millimeter and sex was noted whenever possible by squeezing the abdomen and looking for red or white roe.
Data Analysis
Bivariate linear regression was used to identify significant relationships between environmental parameters and catch data (Townsend 2002). Data were natural log transformed (X + 1) to satisfy the assumption of normality.
The influence of various environmental factors on response variables (catch data) were identified using multifactor ANOVA. The Levene statistic was used to test for homogeneity of variance (Townsend 2002). When a significant difference was detected, a multiple range test was used to identify differences.
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RESULTS
Environmental Factors
Air temperatures during the study period ranged from 10.1−35.7°C (Table 2.2). A comparison of air temperature and fish catch demonstrated a significant relationship
(Figs. 2.2-2.3), with decreased temperature related to increased catches of both M. cephalus (R2=0.045, p<0.0145, n=131) and M. curema (R2=0.043, p<0.0170, n=131).
Water temperatures during the study period ranged from 13.2−34.2°C and also had a similar relationship with M. curema catch (Fig. 2.4; R2=0.041, p<0.0185, n=136).
Dissolved oxygen measurements ranged from 2.17-12.39 mg L-1 during the study period, and an examination of dissolved oxygen and total catch showed a significant inverse relationship (Fig. 2.5; R2=0.033, p<0.0269, n=124).
More M. cephalus were caught on average during the crepuscular hours, with catch being higher during early morning (0400-0800 hrs.) and late afternoon/evening
(1600-2000 hrs and 2000-2400 hrs); however, only the early morning time period was significantly different (F5, 136=2.49, p<0.0462) from the late morning and early afternoon
(Fig. 2.6). A comparison of bottom type and total catch revealed that more fish (all species) were caught over seagrass than mud or sand bottom (F3, 126 = 2.81, p<0.0420;
Fig. 2.7), and catches over oyster bottom did not differ significantly from any other bottom type. Comparing M. curema catch with bottom type, significantly more fish were caught over sand than either seagrass or mud bottom (F3, 126 = 3.18, p<0.0264; Fig.
82
2.8). Again, M. curema catch over oyster bottom did not differ significantly from that over any other bottom type. A comparison of moon phase and number of M. curema catch revealed that significantly more fish were caught during a new moon than any other moon phase (F7,129 = 6.84, p<0.0001; Fig. 2.9).
Fishing Effort Variables
An examination of fish catch by gear type identified significant differences. The combination of simultaneous use of seine nets and cast nets was more effective than either seine nets or cast nets alone for total catch (F2,134 =27.15, p<0.0001; Fig. 2.10) and
M. cephalus catch (F2,134 =13.60, p<0.0001; Fig. 2.11). Both seine nets and combination nets were more effective at catching M. curema than cast nets (F2,134 =6.37, p<0.0023;
Fig. 2.12); furthermore, seine nets caught the most bycatch (F2,134 =33.52, p<0.0001; Fig.
2.13). A larger number of nets per set was more effective for total catch (all species)
(F3,126 =33.79, p<0.0001; Fig. 2.14).
A comparison of mesh size indicated that 2-in. mesh nets caught significantly more M. cephalus than nets with other mesh sizes (F5,124 =24.88, p<0.0001; Fig. 2.15).
However, nets with 2 ¾ in.-mesh size were responsible for more bycatch (F2,134 =3.19, p<0.0059; Fig. 2.16), though bycatch associated with 2 ¾ in. mesh nets was not significantly greater than for 2 and 3 in. mesh nets. A mesh size of 1 7/8 in. caught longer total catch (F2,134 =3.19, p<0.0059; Fig. 2.17), longer Mugilidae (F5,87 =7.95, p<0.0001; Fig.
2.18) and longer M. cephalus (F5,83 = 9.69, p<0.0001; Fig. 2.19). In each case, mean fish
83 length associated with 1 7/8 in mesh was not significantly different than fish length associated with 2 in. mesh.
Characterization of Fishery Variables
Total catch was related to boat size (F6,123 =7.97, p<0.0001; Fig. 2.20) and number of crew (F4,130 =7.97, p<0.0377; Fig. 2.21), with higher catch associated with the use of a
22 ft. skiff and with 3 to 4 crew members versus only one. A comparison of engine sizes revealed that a 115 hp motor was responsible for landing more M. cephalus (F8,121 =7.97, p<0.0001; Fig. 2.22), and a smaller 90 hp motor was responsible for landing significantly more M. curema (F8,121 =2.23, p<0.0296; Fig. 2.23).
An examination of the efficacy of captains showed that captain 4 was most efficient, landing the greatest number of total fish (F7,129 =12.66, p<0.0001; Fig. 2.24), mullet (F7,85 =7.73, p<0.0001; Fig. 2.25), M. cephalus (F7,129 =2.78, p<0.0101; Fig. 2.26), and bycatch (F7,129 =9.54, p<0.0001; Fig. 2.27). In terms of average fish size, captain 7 caught the longest total fish (F7,89 =7.21, p<0.0001; Fig. 2.28), though mean length was not significantly different than for captains 2 and 4; longest mullet (F7,85 =7.73, p<0.0001; Fig. 2.29), though mean length was not significantly different than for captain
2; and longest M. cephalus (F6,82 =5.67, p<0.0001; Fig. 2.30), although again mean length was not significantly different than for captain 2.
An examination of stations showed that the greatest number of fish (F8,128 =6.84, p<0.0001; Fig. 2.31) and bycatch (F8,128 =5.91, p<0.0001; Fig. 2.32) were caught at
84
Coquina Beach. However, longer fish were consistently landed at Palmetto Point: total fish (F8,88 =4.4, p<0.0002; Fig. 2.33), though not significantly different from landings at
Blackburn Point and North Siesta Bridge; mullet (F8,128 =5.91, p<0.0001, though not significantly different from Blackburn Point, North Siesta Bridge, or Turtle Beach; not figured); and M. cephalus (F8,84=6.69, p<0.0001; not figured).
A total of 3,452 fishes comprising 26 species were landed during the sampling period (Table 2.3). The target species, M. cephalus, represented 63.5% of the total catch. Crevalle jack (Caranx hippos) represented the highest landings of bycatch (14.6% of total), followed by striped mojarra (Eugerres plumieri) (8.1%) and silver mullet (Mugil curema) (4.5%).
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DISCUSSION
This research was conducted to better understand how a suite of fishery- dependent and environmental factors is related to mullet catch and accompanying bycatch. The results could be applicable for fishery management plans pertaining to M. cephalus.
Environmental factors
Lower air temperature was associated with increased catch for both M. cephalus and M. curema, and lower water temperature was associated with increased M. curema catch. Regression models did not provide a good fit to the data for either of these relationships. Any observed effects of temperature were likely related to the fact that mullet congregate to spawn in response to cold fronts. For example, Ibáñez and
Gutiérrez-Benítez (2004) observed that spawning migration peaked when temperatures were at their lowest between 14 and 16 °C. Lower dissolved oxygen levels were also associated with a higher total catch. This may be because M. cephalus made up the majority of the catch (63.5%) and have the capability to exhibit aquatic surface respiration, an adaptive process where they ventilate at the surface (making them easier to detect) after feeding on the bottom under hypoxic conditions. (Whitfield et al.
2012). More M. cephalus were caught on average during crepuscular hours, which could be the result of boats and nets being less visible to the mullet during times of lower light.
86
A comparison of catch and bottom type revealed a significantly higher total catch over seagrass. Because seagrass provides many ecosystem functions, such as a good habitat for feeding, shelter from predation, and acts as a nursery for many juvenile fishes, more diversity can be expected (Henderson et al. 2017). Thirty-seven percent of the M. cephalus landed were caught over seagrass. Bycatch caught over seagrass included Pinfish (Lagodon rhomboides), Redfish (Scianenops ocellatus), Common Snook
(Centropomus undecimalis), Spotted Seatrout (Cynoscion nebulosus), Sheepshead
(Archosargus probatocephalus), and Crevalle Jack (Caranx hippos). These results are corroborated by studies conducted in other estuaries that also documented a greater density of fish and preference for dense seagrass habitats compared to non-vegetated sites, particularly among prey species (Bell and Westoby 1986; Rozas and Minello 1998).
The fact that this region is a major contributor to fisheries that greatly depend on the productivity of seagrass habitat to maintain healthy populations reinforces the importance of preserving water quality and natural fish habitat in the region. This is especially true in an area with such high anthropogenic pressure.
Although more total fish were caught over seagrass, more M. curema were associated with sand bottom. As M. curema begin to feed, they may navigate over mud and sand in search of diatoms and phytoplankton that have dropped out of suspension, which may explain why we did not see the same relationship. A comparison of moon phase and number of M. curema revealed that more fish were caught during a new moon than any other moon phase. The relationship between higher numbers of fish and this lunar phase may be linked to the fish’s physiological and internal coordination as
87 suggested by Pearse (1990). A new moon, when tides are strongest, results in greater water movement and therefore fish movement, and may allow for a better opportunity at fishing. However, the relationship did not exist during a full moon, when tides are also strong, suggesting that the low light associated with a new moon may also be a factor. Because the same correlation did not exist with M. cephalus, it is possible that M. curema behavior is more affected by moon phase.
Fishery-Dependent Factors
The combination of simultaneous use of seine nets and cast nets was more effective than either seine nets or cast nets alone at catching all fish and M. cephalus.
Combining nets, the seine net is used to surround the fish and the cast nets are deployed within the seine net, thus eliminating much of the possibility of fish escaping.
The combination technique is useful in more open water where fishers can deploy their gear over a large area of water allowing them greater opportunity to surround many fish. Cast nets were the least effective at catching M. curema, and seine nets caught the most bycatch. Other research has also shown that cast nets were less efficient than seine nets (Stevens 2006). However, cast nets are often preferred because they have several advantages, including the ability to be easily deployed from either shore or a small boat, an important consideration when working over soft sediments for easy retrieval. Cast nets can be used over a variety of depths and habitats with minimal disturbance to the environment, and they are efficient for targeting a specific area.
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Finally, cast nets can be deployed quickly and function with a single user, whereas seine nets require more crew for basic function. Although the seine nets alone caught much more bycatch during this study, they were also effective at catching M. cephalus farther from shore in more open water.
A 2-in. mesh size caught a significantly greater number of M. cephalus than other mesh sizes, likely because the 2-in. mesh size was associated with the most effective gear type, the seine nets used during the combination of seine and cast nets (cast nets during combo gear were 2 ½ in. mesh size). However, 2 ¾ in.-mesh size caught a greater number of bycatch and is associated with cast nets. This result is likely because the 2 ¾ mesh size is conducive for catching fishes of a certain size, such as Crevalle Jack, Striped
Mojarra and Pinfish, which are abundant in the study area. Other mesh sizes may allow these fishes to either pass through the gear or not become easily entangled. A mesh size
7 of 1 /8 in. caught longer total catch, longer Mugilidae and longer M. cephalus. This result was unexpected, because one would expect larger mesh to catch longer fish on average; however, as previously mentioned, the mechanics of mesh size are not straight forward.
A greater catch was associated with a larger boat and a larger crew: a larger boat is beneficial for accommodating more crew and holding more catch. Captain number 4 was more efficient at catching all species combined, number of Mugilidae, number of M. cephalus, and bycatch. Captain number 4 was the only captain to use a combination of seine and cast nets. Captain 7 caught the longest total fish, total Mugilidae, and M.
89 cephalus, and he primarily used the 1 7/8 mesh size.
An examination of stations showed that the highest number of target fish and bycatch were caught at Coquina Beach—the primary fishing location of Captain 4.
However, the longest fish were consistently landed at Palmetto Point (where Captain 7 fished), including the longest mullet (both species) and longest M. cephalus.
The inherent complexity of stock assessments and fisheries management policies, combined with the reality that the results often don’t correlate with the conditions fishers and others observe on the water, lead to the results often being criticized and politicized (LaPointe et al. 2012). Those results are often challenged in the court of law or public opinion by fishers who believe the assessments are too pessimistic or by environmentalists and the public who believe they are too optimistic. This research is important for bridging the gap between scientists and fishers and provided opportunities for a scientist to gain first-hand experience with the fishery on the water.
Because catch per unit effort increased during times of low air and water temperatures, which are related to spawning season, it is also important to protect the species during these times with appropriate management measures. These may include restricted fishing in the form of limited licenses, weight limits, restricted areas, or closures. Because the most effective gear, with less bycatch, was a combination of cast and seine nets, policy makers may want to reconsider adjusting laws to allow for the use of more nets. Measures should also be taken to control the number of dead fish released overboard (bycatch or male mullet during roe season). Although the practice of discarding dead fish was not observed during this project, it has been reported as a
90 significant environmental threat to the fishery. Fishers can also use the data pertaining to mesh size to better target fish by species and minimize bycatch. Maintaining resilient fishery ecosystems involves more than fisheries management: there are multiple stakeholders involved in other factors that affect fisheries, such as land use, policy- making, and economic and social systems. Adaptive strategies to ensure the sustainability of fisheries and the ecosystems that support them require interactions among all of these components, as well as long-term, effective monitoring.
Limitations/Future Research
The results of this study demonstrate that fisher behavior heavily influenced catch rates. Because sampling was based on natural fishing behavior and the captain chose the optimal fishing conditions, this bias limits the ability to link environmental factors to catch rates. Additionally, the original scope of this project was designed to examine one gear type, cast nets. However, during some fishing trips it was more efficient for the captain to also use a seine net, alternating gear, or a combination of the two. Only one set contained the combination gear method, and the results were heavily influenced by the efficiency of that gear. Future research should compare fishery- dependent data, such as that collected in the present study, with fishery-independent data for a more comprehensive analysis, as fishery-independent data is collected using standardized gear and randomly stratified sampling. The fishery appears to be complex, so additional data could also be useful to gain a better understanding of the interactions
91 between variables such as dissolved oxygen concentration, temperature, location, and gears fished.
This project demonstrated that it is feasible to collect relevant scientific data useful for fisheries management onboard small, commercial inshore vessels. It was successful at characterizing a typical mullet fishing trip in southwest Florida, including gathering data about fishing effort, gear usage, catch composition and bycatch information. This innovative approach to data collection supports overall ecosystem based management approaches for Southwest Florida, and its implementation should be considered by fisheries managers.
Although mullet are historically known as a trash fish, they play an important role in energy flow within coastal and estuarine ecosystems. Because mullet feed at a lower trophic level, many species higher in the food chain depend on them as a food source, and thus they are subject to high rates of predation. Therefore, future fishery- related models should include such elements as predator-prey interactions and the effects of habitat quality and quantity. Mullet should also be considered as part of
Ecosystem-based Management Plans in the Gulf of Mexico. Biological and population parameter estimates needed for stock assessment models should be updated through fishery-independent sampling (Mahmoudi 2014). Because this was a pilot, feasibility study, data analysis was limited to univariate approaches. Future research should therefore examine the fishery using a multivariate approach to identify potential suites of factors that may result in spatial and temporal differences in catch that were not detected in the current study. Future research should also investigate the effects of red
92 tide, especially during roe season when mullet are more active in coastal waters outside estuaries, as well as the potential impacts of climate change, as Striped Mullet is a temperature-driven spawner. It is hopeful these results have implications for current fishing practices with the possibilities of modifying fishing strategies to reduce operational costs, bycatch, loss of target fish at sea, and detrimental impacts on the environment.
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TABLES
Table 2.1. Commercial M. cephalus sampling trips September 2012-January 2014.
Date Station Fisherman Gear 9/7/2012 Turtle Beach, Sarasota 3 Cast net 11/5/2012 10th St Marina, Sarasota 1 Cast net 12/7/2012 Turtle Beach, Sarasota 3 Cast net 1/14/2013 10th St Marina, Sarasota 1 Cast net 5/9/2013 Cortez, Bradenton 6 Cast net 5/17/2013 Cortez, Bradenton 6 Cast net 6/19/2013 Alligator Creek, Punta Gorda 5 Seine/Cast net 7/12/2013 Alligator Creek, Punta Gorda 5 Cast net 8/5/2013 10th St. Marina, Sarasota 1 Cast net 8/13/2013 Alligator Creek, Punta Gorda 5 Cast net 8/29/2013 Palmetto Boat Ramp, Palmetto 7 Cast net 9/27/2013 Palmetto Boat Ramp, Palmetto 7 Cast net 10/7/2013 10th St Marina, Sarasota 1 Cast net 10/18/2013 Alligator Creek, Punta Gorda 5 Cast net 10/22/2013 Coquina Beach, Bradenton 4 Combo/Seine 11/11/2013 10th St Marina, Sarasota 1 Cast net 11/14/2013 10th St Marina, Sarasota 1 Cast net 11/22/2013 Alligator Creek, Punta Gorda 5 Cast net 11/29/2013 Alligator Creek, Punta Gorda 5 Cast net 12/03/2013 Alligator Creek, Punta Gorda 5 Seine/Cast net 12/4/2013 10th St Marina, Sarasota 1 Cast net 12/6/2013 Coquina Beach, Bradenton 8 Cast net 12/10/2013 10th St Marina, Sarasota 4 Cast net 12/12/2013 10th St Marina, Sarasota 4 Cast net 12/13/2013 North Siesta Bridge, Sarasota 2 Cast net 12/17/2013 North Siesta Bridge, Sarasota 2 Cast net
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12/18/2013 North Siesta Bridge, Sarasota 2 Cast net 12/20/2013 Nokomis Beach, Nokomis 2 Cast net 1/5/2014 Nokomis Beach, Nokomis 2 Cast net 1/6/2014 North Jetty Park, Venice 8 Cast net
Table 2.2. Mean and standard errors of environmental variables by location.
Mean Baro Days Mean Air Mean Water Mean Salinity Mean Cloud Distance Shore Location Mean DO% Pressure (in Fished Temp (C) Temp (C) (ppt) Cover % (m) Hg)
10th St Marina 8 22.0 (0.6) 23.5 (0.5) 32.6 (0.2) 81.6 (2.9) 30.2 (0.1) 62.6 (6.3) 16.3 (5.1)
Coquina Beach 4 26.6 (2.0) 25.7 (1.3) 30.9 (2.7) 95.7 (4.7) 30.0 (0.1) 7.0 (1.7) 463.0 (230.7)
Cortez 2 29.0 (0.9) 26.0 (0.4) 33.2 (1.3) 94.6 (5.6) 30.1 (0.0) 0.0 (0.0) 7.6 (1.8)
Blackburn 2 17.2 (1.2) 18.0 (0.3) 34.0 (0.1) 58.7 (8.4) 30.2 (0.0) 32.0 (19.6) 18.0 (1.2) Point North Siesta 3 14.8 (1.1) 19.1 (0.3) 32.2 (1.3) 79.7 (4.0) 30.3 (0.0) 5.0 (3.4) 17.4 (7.4) Bridge
Palmetto Point 2 29.4 (0.7) 31.1 (0.6) 22.5 (1.6) 118.5 (14.7) 29.9 (0.0) 18.5 (3.4) 9.2 (3.0)
Gator Creek 7 28.0 (1.0) 26.8 (1.0) 20.2 (1.1) 64.9 (4.3) 30.0 (0.0) 24.2 (5.0) 13.2 (6.6) Marina
Turtle Beach 3 24.7 (1.0) 26.7 (0.9) 33.9 (0.4) 103 (3.3) 29.5 (0.4) 0.0 (0.0) 23.8 (17.6)
North Jetty 1 19.6 (1.0) 19.4 (0.3) 33.7 (1.3) 83.5 (6.8) 30.0 (0.0) 100.0 (0.0) 8.3 (1.7) Park
95
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Table 2.3. Species caught and percentage of total catch.
Species Common name Catch (#) % Total Catch Archosargus probatocephalus Sheepshead 86 2.5 Ariopsis felis Hardhead Catfish 10 0.3 Caranx bartholomaei Yellow Jack 1 0.0 Centropomus undecimalis Common Snook 26 0.8 Chaetodipterus faber Atlantic Spadefish 3 0.1 Caranx hippos Crevalle Jack 505 14.6 Cynoscion arenarius Sand Seatrout 2 0.1 Cynoscion nebulosus Spotted Seatrout 12 0.3 Dasyatis americana Southern Stingray 1 0.0 Diplodus holbrookii Spottail Pinfish 1 0.0 Eugerres plumieri Striped Mojarra 280 8.1 Haemulon plumieri White Grunt 6 0.2 Acanthostracion quadricornis Scrawled Cowfish 1 0.0 Lagodon rhomboides Pinfish 101 2.9 Lutjanus griseus Gray Snapper 28 0.8 Megalops atlanticus Tarpon 1 0.0 Micropogonias undulatus Atlantic Croaker 3 0.1 Mugil cephalus Striped Mullet 2193 63.5 Mugil curema Silver Mullet 154 4.5 Paralichthys albigutta Gulf Flounder 1 0.0 Pogonias cromis Black Drum 5 0.1 Sciaenops ocellatus Red Drum 27 0.8 Selene vomer Lookdown 2 0.1 Sphoeroides nephelus Southern Puffer 1 0.0 Sphyrna tiburo Bonnethead Shark 1 0.0 Synodus foetens Inshore Lizardfish 1 0.0
97
FIGURES
Figure 2.1. Map of the study area and sampling stations.
(Ln X + + 1) X (Ln
M. cephalusM.
Number of of Number (
Air Temp °C
Figure 2.2. Results of linear regression comparing M. cephalus catches (Ln X + 1) and air temperature (R2=0.045, p<0.0145, n=131).
98
(Ln X + X (Ln 1)
curema
M.
(Ln)
Number of of Number (
Air Temp °C°C
Figure 2.3. Results of linear regression comparing M. curema catch (Ln X + 1) and air temperature (R2=0.043, p<0.0170, n=131).
99
(Ln X + X (Ln 1)
curema
M.
(Ln)
Number of of Number (
Water Temp °C
Figure 2.4. Results of linear regression comparing M. curema catch (Ln X + 1) and water temperature (R2= p<0.041, n=136).
100
(Ln X (Ln + 1)
(Ln)
Total no. Total of fish (
Figure 2.5. Results of linear regression comparing total fish (all species) catch (Ln X + 1) compared to dissolved oxygen (R2=0.033, p<0.0269, n=124).
101
6 1 ab 5
4 27 12 per set (Ln X + 1) + X (Ln set per b 3 80 ab 16 a
2 a M. cephalus cephalus M. 1 0 0 0 Mean no. no. Mean 0100-0400 0401-0800 0801-1200 1201-1600 1601-2000 2001-2400
Time of day
Figure 2.6. Results of ANOVA comparing mean catch of M. cephalus (Ln X + 1) per set and time of day. Vertical bars are standard errors. Letters denote significant differences (F5, 136=2.49, p<0.0462). Numbers denote number of sets. No sets were made 0100-0400 hrs.
102
60 32 b 2 50 ab 40 60
36 a 30 a
20 Mean no. fish per set per fish no. Mean
10
0 Mud Oyster Sand Seagrass
Bottom type
Figure 2.7. Results of ANOVA comparing mean number of fish (all species) per set and bottom type. Vertical bars are standard errors. Letters denote significant differences (F3, 126 = 2.81, p<0.0420). Numbers denote number of sets.
103
2 0.9 ab 0.8 60 0.7 b 0.6
0.5
32 per set (Ln X + 1) + X (Ln set per 0.4 36 a 0.3 a
M. curemaM. 0.2
0.1
0 Mean no. Mean Mud Oyster Sand Seagrass
Bottom type
Figure 2.8. Results of ANOVA comparing mean number M. curema (Ln X + 1) per set and bottom type. Vertical bars are standard errors. Letters denote significant differences (F3, 126 = 3.18, p<0.0264). Numbers denote number of sets.
104
6 12 b
10 per set per 8
6 M.curema
5 4 28 13 40 40 a a a Mean no. Mean 2 a 2 a 3 0 0 0 New Waxing First Waxing Full moon Waning Last Waning moon crescent quarter gibbous gibbous quarter cresent Moon phase
Figure 2.9. Results of ANOVA comparing mean number of M. curema per set and moon phase. Vertical bars are standard errors. Letters denote significant differences (F7,129 = 6.84, p<0.0001). Numbers denote number of sets.
105
1 250 c
200
150 10
b 100
Mean no. fish per set per fish no. Mean 126 50 a
0 Cast net Seine Combination
Gear type
Figure 2.10. Results of ANOVA comparing mean number of fish (all species) per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =27.15, p<0.0001). Numbers denote number of sets.
106
250 1 b
200 per set set per
150
M. cephalus cephalus M. 100
10 126
50 a Mean no. Mean a
0 Cast net Seine Combination
Gear type
Figure 2.11. Results of ANOVA comparing mean number of M. cephalus per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =13.60, p<0.0001). Numbers denote number of sets.
107
1 12 b
10
10 per set per 8 b
6 M. curemaM.
4 126
Mean no. Mean 2 a
0 Cast net Seine Combination
Gear type
Figure 2.12. Results of ANOVA comparing mean number of M. curema per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =6.37, p<0.0023). Numbers denote number of sets.
108
10 80 b 70
60
50
40 1
30 a
20 126 Mean no. bycatch per set per bycatch no. Mean
10 a
0 Cast net Seine Combination
Gear type
Figure 2.13. Results of ANOVA comparing mean number of bycatch per set and gear type. Vertical bars are standard errors. Letters denote significant differences (F2,134 =33.52, p<0.0001). Numbers denote number of sets.
109
1 350 b
300
250
200
150 16 100 25 Mean no. fish per set per fish no. Mean 88 a 0 0 a 50 a 0 0 0 1 2 3 4 5 6
Nets used per set
Figure 2.14. Results of ANOVA comparing number of nets used and mean number of fish per set. Vertical bars are standard errors. Letters denote significant differences. Numbers denote number of sets. No boats used 4 or 5 nets per set (F3,126 =33.79, p<0.0001).
110
1
600 b
500 per set per 400
300 M. cephalus cephalus M. 200 10 16 29 66 8 Mean no no Mean 100 a a a a a 0 1 7/8 2 2 1/2 2 3/4 2 7/8 3
Mesh size (in.)
Figure 2.15. Results of ANOVA comparing mean number M. cephalus per set and mesh size. Vertical bars are standard errors. Letters denote significant differences (F5,124 =24.88, p<0.0001). Numbers denote number of sets.
111
29 35 1 b 30 ab 8 25 ab 20 10
15 a 16 66 a 10 a
Mean no. bycatch per set per bycatch no. Mean 5
0 1 7/8 2 2 1/2 2 3/4 2 7/8 3
Mesh size (in.)
Figure 2.16. Results of ANOVA comparing mean number of bycatch per set and net mesh size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F2,134 =3.19, p<0.0059).
112
1 8 500 abc 54 450 c 18 6 10 400 ab b ab a 350 300 250 200 150 100
Mean fish FL (mm) set per (mm) FL fish Mean 50 0 1 7/8 2 2 1/2 2 3/4 2 7/8 3
Mesh size (in.)
Figure 2.17. Results of ANOVA comparing mean fish fork length per set and net mesh size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F2,134 =3.19, p<0.0059).
113
1 8 51 450 18 6 c abc 9 b 400 a a a 350
300
FL (mm) per set per (mm) FL 250
200
150 Mugilidae 100
Mean Mean 50
0 1 7/8 2 2 1/2 2 3/4 2 7/8 3
Mesh size (in.)
Figure 2.18. Results of ANOVA comparing mean mullet (both species) fork length per set by net mesh size.
Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F5,87 =7.95, p<0.0001).
114
8 1 7 49 450 d abcd 18 6 bc c 400 a ab
per set set per 350
300
FL (mm) FL 250
200
150
M. cephalus cephalus M. 100
50 Mean Mean 0 1 7/8 2 2 1/2 2 3/4 2 7/8 3
Mesh size (in.)
Figure 2.19. Results of ANOVA comparing mean M. cephalus fork length per set and net mesh size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F5,83 = 9.69, p<0.0001).
115
11 120 b
100
80 5 a 60 5 46 11 40 40 12 a a Mean no. fish per set per fish no. Mean a a 20 a
0 12 14 16 18 19 22 24
Boat size (ft.)
Figure 2.20. Results of ANOVA comparing mean number of fish per set and boat size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F6,123 =7.97, p<0.0001).
116
24 5 79 5 b b 22 4.5 ab
4 a
3.5
3
2.5
2
1.5
Mean no. fish per set (Ln) set per fish no. Mean 1
0.5
0 1 2 3 4
Number of crew
Figure 2.21. Results of ANOVA comparing mean number of fish per set and number of crew. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F4,130 =7.97, p<0.0377).
117
8 80 b 70
per set per 60
50 13 40 15 3 8 18 5
M. cephalus cephalus M. a 48 a a 30 12 a a a a 20 a
10 Number of Number
0 15 25 60 90 100 115 140 150 225
Engine size (hp)
Figure 2.22. Results of ANOVA comparing mean M. cephalus fork length per set and engine size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,121 =7.97, p<0.0001).
118
60 90
50 b
per set per 40
140 30 60 15 a 150 M. curema M. a 20 25 115 a 225 a 100 a a
10 a a Number of Number 0 15 25 60 90 100 115 140 150 225
Engine size (hp)
Figure 2.23. Results of ANOVA comparing mean M. curema fork length per set and engine size. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,121 =2.23, p<0.0296).
119
8 160 b 140
120
100
80 10 60 32 40 13 17 a 5 a 12 Mean no. fish per set per fish no. Mean 40 a a a a 20 a
0 1 2 3 4 5 6 7 8
Captain
Figure 2.24. Results of ANOVA comparing mean number of fish (all species) per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,129 =12.66, p<0.0001).
120
8 80 b
70
60 per set per 50 10 13 40 a Mugilidae 40 5 a 17 32 30 12 a a a a
20 a Mean no. Mean 10
0 1 2 3 4 5 6 7 8
Captain
Figure 2.25. Results of ANOVA comparing mean number of mullet (both species) per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,85 =7.73, p<0.0001).
121
8 80 b 70
60 per set per 50 10 13 40 a a 5 40 17 32 M. cephalus cephalus M. 30 12 a a a a 20 a
Mean no. Mean 10
0 1 2 3 4 5 6 7 8 Captain
Figure 2.26. Results of ANOVA comparing mean number of M. cephalus per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,129 =2.78, p<0.0101).
122
8 80 c
70
60
50
40 32 30 12 10 5 13 17 b 20 40 ab ab Mean no. bycatch per set per bycatch no. Mean ab ab ab 10 a
0 1 2 3 4 5 6 7 8
Captain
Figure 2.27. Results of ANOVA comparing mean number of bycatch per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,129 =9.54, p<0.0001).
123
8 34 9 3 450 7 24 9 d c cd bcd 400 bc b bc 350 3 300 a 250 200 150 100
Mean fish FL (mm) set per (mm) FL fish Mean 50 0 1 2 3 4 5 6 7 8
Captain
Figure 2.28. Results of ANOVA comparing mean fish fork length per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,89 =7.21, p<0.0001).
124
8 32 9 7 450 3 c cd 23 d bc 9 400 bc b b 2 350 a
300 (mm) per set per (mm) 250
200
150
Mugilidae FL FL Mugilidae 100
50 Mean Mean 0 1 2 3 4 5 6 7 8
Captain
Figure 2.29. Results of ANOVA comparing mean mullet (both species) fork length per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F7,85 =7.73, p<0.0001).
125
8 31 8 3 450 7 23 bc 9 c 400 b ab ab ab a
350 per set per 300
250
200 M. cephalus cephalus M. 150
100
0 Mean FL FL Mean 50 0 0 1 2 3 4 5 6 7 8
Captain
Figure 2.30. Results of ANOVA comparing mean M. cephalus fork length per set and captain. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F6,82 =5.67, p<0.0001). No M. cephalus were measured during trips with captain 8.
126
3
120 b
100
80
8 60 4 4 23 31 a 3 a a 7 40 9 a a a a Mean no. fish per set per fish no. Mean a 20
0 10th st Coquina Cortez Blackburn North Palmetto Alligator Turtle North Marina Beach Point Siesta Point Creek Beach Jetty Park Bridge Station
Figure 2.31. Results of ANOVA comparing mean number of fish per set by station. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,128 =6.84, p<0.0001).
127
10 70 c 60
50
40 32 30 3 40 12 8 10 b 17 20 ab a ab 5 ab ab ab 10 Mean no. bycatch per set per bycatch no. Mean 0 0 10th st Coquina Cortez Nokomis North Palmetto Alligator Turtle North Marina Beach Beach Siesta Point Creek Beach Jetty Park Bridge Station
Figure 2.32. Results of ANOVA comparing mean number of bycatch per set and station. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,128 =5.91, p<0.0001).
128
8 4 4 31 450 9 c 7 3 bc bc 23 400 bc ab ab 3 a a 350 a
300 250
200 150
100
50 Mean fish FL (mm) set per (mm) FL fish Mean 0 10th st Coquina Cortez Blackburn North Palmetto Alligator Turtle North Marina Beach Point Siesta Point Creek Beach Jetty Park Bridge Station
Figure 2.33. Results of ANOVA comparing mean total fish fork length per set and station. Vertical bars are standard errors. Numbers denote number of sets. Letters denote significant differences (F8,88 =4.4, p<0.0002).
129
130
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