4.0 Species’ Biology, Distribution and Status

4.1 Species under management by the South Atlantic Council

4.1.1 Penaeid and Deepwater

4.1.1.1 Penaeid Shrimp

Description and distribution The shrimp fishery in the South Atlantic includes six species: brown shrimp (Farfantepeneaus aztecus), pink shrimp (Farfantepenaeus duorarum), white shrimp (), seabob shrimp ( kroyeri), rock shrimp (Sicyonia brevirostris), and royal red shrimp (Pleoticus robustus). The shrimp species of the southeastern U.S. occupy similar habitats with the greatest differences being in optimal substrate and salinity.

White shrimp Common names for the white shrimp (Figure 4.1-1) include gray shrimp, lake shrimp, green shrimp, green-tailed shrimp, blue tailed shrimp, rainbow shrimp, Daytona shrimp, common shrimp, and southern shrimp.

Figure 4.1-1. White shrimp, Litopenaeus setiferus (Williams 1984).

White shrimp range from Fire Island, New York to St. Lucie Inlet on the Atlantic Coast of Florida. Along the Atlantic Coast of the U.S., the white shrimp has centers of abundance in South Carolina, Georgia, and northeast Florida. White shrimp are generally concentrated in waters of 27 m (89 ft) or less, although occasionally found much deeper (up to 270 ft).

Brown shrimp The brown shrimp (Figure 4.1-2) is also known as brownie, green lake shrimp, red shrimp, redtail shrimp, golden shrimp, native shrimp, and also the summer shrimp in North Carolina.

Figure 4.1-2. Brown shrimp, Farfantepenaeus aztecus (Williams 1984).

On the Atlantic Coast, brown shrimp occur from Martha’s Vineyard, Massachusetts to the Florida Keys. While it may occur seasonally along the Mid-Atlantic states, breeding populations apparently do not range north of North Carolina. The species may occur in commercial quantities in waters as deep as 110 m (361 ft), but they are most abundant in water less than 55 m (180 ft).

Pink shrimp Other names for the pink shrimp (Figure 4.1-3) include spotted shrimp, hopper, pink spotted shrimp, brown spotted shrimp, grooved shrimp, green shrimp, pink night shrimp, red shrimp, skipper, and pushed shrimp.

Figure 4.1-3. Pink shrimp, Farfantepenaeus duorarum (Williams 1984).

Along the Atlantic, pink shrimp occur from southern Chesapeake Bay to the Florida Keys. Maximum abundance is reached off southwestern Florida. Pink shrimp are most abundant in waters of 11-37 m (36-121 ft) although in some areas they may be abundant as deep as 65 m (213 ft). Pink shrimp are common in the estuaries and shallow marine waters surrounding southern Florida and into deepwater (approximately 100 meters) southeast of the Keys, and are the dominant species within the Dry Tortugas shrimping grounds and Florida Bay (Solamon 1968).

Seabob shrimp

Figure 4.1-4. Seabob shrimp, Xiphopenaeus kroyeri (FAO FIGIS Species Factsheet 2007. Available online at http://www.fao.org/fi/website/FIRetrieveAction.do?dom=species&fid=2600)

Seabob shrimp (Figure 4.1-4) range from North Carolina to Estado de Santa Catarina (). Seabobs inhabit waters from 1 to 70 m, usually less than 27 m over mud or sand bottom. They are found in marine, brackish and exceptionally fresh waters and are most plentiful in areas near river estuaries. This species is of limited commercial importance off the southeast Atlantic coast (see William, 1984 for review). Burkenroad (1949) found ripe or nearly ripe females off North Carolina in May. Information on the biology of seabob shrimp is scant so the discussion in following sections pertains only to the other three penaeid species in the management unit.

Reproduction White Shrimp White shrimp attain sexual maturity at about 35-140 mm (5.3-5.5 in) total length (TL). Fecundity for all penaeid species ranges from 500,000 to 1,000,000 ova. Eggs are demersal (sink to the bottom) and measure 0.28 mm in diameter (SAFMC 1996b).

Off Georgia and northern Florida, some white shrimp spawning may occur inshore, although most spawning occurs more than 1.2 miles from the coastline. Off Florida, spawning occasionally takes place inshore, at or near inlets, but most occurs offshore in depths of 6.1 to 24.4 m (20-80 ft). In South Carolina, most spawning occurs within about four miles of the coast. Spawning is correlated with bottom water temperatures of 17° to 29°C (62.6 to 84.2° F) although spawning generally occurs between 22° and 29°C (71.6 and 84.2° F). White shrimp begin spawning during April off Florida and Georgia, and late April or May off South Carolina (Lindner and Anderson 1956). Spawning may continue into September or October (SAFMC 1996b).

Brown shrimp Similar to white shrimp, brown shrimp reach sexual maturity at about 140 mm TL (5.5 in). Eggs are demersal and measure 0.26 mm in diameter (SAFMC 1996b).

Brown shrimp spawn in relatively deep water. In the Gulf of , it was concluded that brown shrimp did not spawn in water less than 13.7 m (45 ft) deep and the greatest percentage of ripe females were at 45.7 m (150 ft) (Renfro and Brusher 1982). Spawning season for brown shrimp is uncertain, although there is an influx of postlarvae into the estuaries during February and March (Bearden 1961; DeLancey et al. 1994). Mature males and females have been found off South Carolina during October and November (SAFMC 1996b).

Pink Shrimp Pink shrimp reach sexual maturity at about 85 mm TL (3.3 in). Eggs are demersal measuring 0.31-0.33 mm in diameter (SAFMC 1996b).

Pink shrimp apparently spawn at depths of 3.7 to 15.8 m (12 to 52 ft). Off eastern Florida, peak spawning activity probably occurs during the summer. In North Carolina, roe-bearing females are found as early as May, and by June, most pink shrimp are sexually mature (Williams 1955).

Development, growth and movement patterns All three penaeid species have 11 larval stages before developing into postlarvae. Duration of the larval period is dependent on temperature, food and habitat. Records suggest larval periods of 10 to12 days for white shrimp, 11 to 17 days for brown shrimp and 15 to 25 days for pink shrimp. Brown shrimp postlarvae appear to overwinter in offshore bottom sediments. Postlarval sizes are similar for white and pink shrimp ranging from approximately 2.9 to 12 mm TL (0.1-0.5 in); brown shrimp are usually larger (SAFMC 1996b).

The mechanisms that transport penaeid shrimp postlarvae from distant spawning areas to inside estuaries are not well known. Shoreward countercurrents north of Cape Canaveral have been suggested as a mechanism for transport of pink shrimp postlarvae from spawning areas to nursery areas along the northeast Florida coast (Kennedy and Barber 1981). Favorable winds may enhance movement of postlarvae toward oceanic inlets (Wenner et al. 1998).

White shrimp Movement of white shrimp postlarvae into the estuary is most likely a result of nearshore tidal currents as white shrimp spawn relatively close to shore. In the South Atlantic, white shrimp enter the estuaries at about the same time as pink shrimp, usually beginning in April and early May in the southern part of their range and in June and July in North Carolina sounds where white shrimp are relatively less abundant than in more southern states.

Smaller (juvenile and subadult) individuals may overwinter inside estuaries forming part of the overwintering stock (SAFMC 1996b). Harsh winter conditions such as cold water temperatures and rainfall can affect the survival of overwintering stocks and subsequent year-class strength.

Large white shrimp begin emigrating out of the estuary to the commercial fishing areas in mid- summer. In North Carolina, white shrimp begin entering the commercial fishery in July and continue to be caught through December (Williams 1955). In Florida, white shrimp leave inshore waters at about 120 mm TL (4.7 in). This movement to offshore waters may be caused by cold weather, storms, high tides and/or large influxes of fresh water, but size is the principal determinant (SAFMC, 1996b). The migrating white shrimp, called roe shrimp, make up the spring fishery and also produce the summer and fall crops of shrimp. When a majority of white shrimp do not survive the winter, the North Carolina and South Carolina fisheries are believed to be dependent on a northward spring migration of white shrimp from more southerly areas to form the spawning stock. However, tagging data are inconclusive on the extent of this northward movement, and recruitment of postlarvae from southern spawning stocks may account for much of the replenishment of the populations.

White shrimp grow from 1.0 to 2.3 mm (0.04 to 0.09 in) per day (SAFMC 1993). Salinity is a factor determining growth rate in white shrimp. Although field studies indicate that juvenile white shrimp prefer low salinities, laboratory studies have revealed that they tolerate a wide range of salinities; they have been successfully reared at salinities of 18 to 34 ppt (Perez-Farfante 1969). Nevertheless, McKenzie and Whitaker (1981) cited several studies in which fast growth was reported for white shrimp at lower salinities of 7 to 15 ppt. The lowest salinity in which white shrimp were recorded in the northern Gulf of Mexico was 0.42 ppt (Perez-Farfante 1969). High salinities appear to inhibit growth in white shrimp, but for brown shrimp, salinities in excess of 10 ppt seem to enhance growth rate. Relatedly, during years of low densities, the average size of white shrimp is generally larger.

Water temperature directly or indirectly influences white shrimp spawning, growth, habitat selection, osmoregulation, movement, migration and mortality (Muncy 1984). Spring water temperature increases trigger spawning, and rapid water temperature declines in fall portend the end of spawning (Lindner and Anderson 1956). Ingress of white shrimp postlarvae has also been linked to temperature (Wenner et al. 2002). Growth is fastest in summer and slowest or negligible in winter. Water temperatures below 20°C (68°F) inhibit growth of juvenile shrimp (Etzold and Christmas 1977) and growth is virtually nil at 16°C (61°F) (St. Amant and Lindner 1966). Growth rates increase rapidly as temperatures increases above 20°C (68°F). Temperature and food supply limited the growth of white shrimp postlarvae more than did salinity differences between 2 and 35 ppt (Zein-Eldin 1964). Freshwater inflow may affect coastal water temperatures, which in turn affect the growth rates (White and Boudreaux 1977) and migration of white shrimp (Shipman 1983b). Increased water temperatures also affect molting rate (Perez- Farfante 1969)

Brown shrimp Movement of brown shrimp appears to take place primarily at night with peak movement at, or shortly after dusk. In the South Atlantic, juvenile and adult brown shrimp are rarely affected by severe winter weather because most surviving shrimp have moved offshore prior to the onset of cold weather (SAFMC 1996b). Brown shrimp first enter the commercial fishery in North Carolina in June at about 100 mm TL (4 in).

Brown shrimp grow 0.5 to 2.5 mm (0.02 – 0.1 in) per day (SAFMC 1993). Salinity is a factor determining growth rate in brown shrimp. Temperature also affects brown (and pink) shrimp growth rates, with rates as high as 3.3 mm (0.13 in) per day recorded when temperature exceeded 25°C (77° F) but less than 1.0 mm (0.04 in) per day when water temperature was below 20°C (68° F). Gaidry and White (1973) stated that years of low commercial landings of brown shrimp were associated with prolonged estuarine temperatures of less than 20°C (68°F) at the time of postlarval immigration into the estuary. Aldrich et al. (1968) demonstrated in laboratory experiments that brown shrimp postlarvae burrowed in the sediment when water temperature was reduced to 12°-16.5°C (54°-62°F). Brown shrimp postlarvae may overwinter in offshore waters and migrate into estuaries the following spring (Aldrich et al., 1968).

Pink shrimp Pink shrimp leave Florida estuaries two to six months after having arrived as postlarvae. In North Carolina, young pink shrimp enter the commercial catch in August. Recruitment to the area offshore of Cape Canaveral begins in April and May and again during October and November (SAFMC 1996b). In North Carolina, pink shrimp begin entering the estuaries in June and July. In Florida, larvae can take two routes to the estuarine nursery areas where they spend most of their life cycle. One route is directly to the shallow-water estuaries of 10,000 Island, Whitewater Bay, and Florida Bay. On the other route, larvae are swept southwesterly into the Florida Current by way of the Loop Current, and are carried northeasterly along the outer edge of the Florida Reef Tract or east coast of Florida (Ingle et al. 1959).

Pink shrimp that overwinter inside estuaries are susceptible to mortality induced by cold weather. However, pink shrimp bury deeply in the substrate with the onset of cold weather and are protected to some extent from winter mortalities (Purvis and McCoy 1972). Pink and white shrimp that survive the winter grow rapidly in late winter and early spring before migrating to the ocean. Pink shrimp that overwinter in estuaries migrate to sea in May and June, at which time spawning takes place. Recruitment to the area offshore of Cape Canaveral begins in April and May and again during October and November (SAFMC 1996b).

Pink shrimp grow 0.25 to 1.7 mm (0.01 – 0.07 in) per day (SAFMC 1993). In Florida Bay, pink shrimp were found to grow 3.5 mm Carapace Length (CL) (0.14 in) in winter and only 1.9 mm CL (0.07 in) in spring (SAFMC 1993). In North Carolina, maximum pink shrimp growth rates were recorded in summer (SAFMC 1993).

Ecological relationships The inshore phase of the penaeid life cycle is perhaps the most critical because this is a period of rapid growth. Estuarine nursery areas, dominated by the marsh grass, Spartina alterniflora, provide abundant food, suitable substrate, and shelter from predators for postlarval shrimp.

Juvenile shrimp appear to be most abundant at the Spartina grass-water interface. This “estuarine edge” is the most productive zone in many estuaries. Because there is a minimum of wind generated turbulence and stabilization of sediments, rich bands of organic material are found along the edges of marshes (Odum 1970). Furthermore, Odum (1970) found the percentages of organic detritus in sediments along the shore in the Everglades estuary are several times greater than a few meters offshore. Mock (1967) examined two estuarine habitats, one natural and one altered by bulkheading. He found a 0.6 m (2 ft) band of rich organic material along the natural shore and very little organic material along the bulkheaded shore. White shrimp were 12.5 times and brown shrimp 2.5 times more numerous in the natural area as in the altered area. Loesch (1965) found that juvenile white shrimp in Mobile Bay were most abundant nearshore in water less than 0.6 m (2 ft) deep containing large amounts of organic detritus. Brown shrimp were congregated in water 0.6 to 0.9 m (2-3 ft) deep where there was attached vegetation.

White shrimp appear to prefer muddy or peaty bottoms rich in organic matter and decaying vegetation when in inshore waters. Offshore they are most abundant on soft muddy bottoms (Lindner and Cook, 1970). Brown shrimp appear to prefer a similar bottom type and as adults may also be found in areas where the bottom consists of mud, sand, and shell. Pink shrimp are found most commonly on hard sand and calcareous shell bottom (Williams 1955, 1984). Both brown and pink shrimp generally bury in the substrate during daylight, being active at night. White shrimp do not bury with the regularity of pink or brown shrimp.

Juvenile and adult penaeids are omnivorous (eating both plants and ) bottom feeders, with most feeding activity occurring at night, although daytime feeding may occur in turbid waters (Darnell 1958; Broad 1965). Food items may consist of polychaetes, amphipods, nematodes, caridean , mysids, copepods, isopods, amphipods, ostracods, mollusks, foraminiferans, chironomid larvae, and various types of organic debris. In addition, aggregations of shrimp have been shown to increase community metabolism and inorganic nitrogen available to phytoplankton (Vetter and Hopkinson 1985).

Shrimp are preyed on by a wide variety of species at virtually all stages in their life history (Gunter 1957). Predation on postlarvae has been observed by sheepshead minnows, water boatmen, and insect larvae. Grass shrimp, killifishes, and blue prey on young penaeid shrimp, and a wide variety of finfish are known to prey heavily on juvenile and adult penaeid shrimp (Minello and Zimmerman 1983). Abundance and status of stocks Population sizes of brown, pink, and white shrimp are believed to be primarily regulated by environmental conditions and available habitat. Penaeid (brown, pink and white) shrimp have an annual life cycle, where adults spawn offshore and the larvae are transported to coastal estuaries. Recruitment to the estuaries and eventually to the fishing grounds is extremely dependent on fluctuations of environmental conditions within estuaries. Poor recruitment to the fishery may occur because of excessively cold winters or heavy rains that reduce salinities and cause high mortality of post-larvae. Conversely, high recruitment to the fishery may occur when environmental conditions are favorable for postlarval development. Effort in the penaeid fishery has been relatively stable over the last 20 years; therefore, catches in any given year may show large fluctuations depending on the magnitude of successful recruitment of young shrimp as they emigrate from the estuaries to offshore waters.

Although shrimp trawling certainly reduces population size over the course of a season, the impact of fishing on subsequent year-class strength is unknown. Natural mortality rates are very high, and coupled with fishing mortality, most of the year class may be removed by the end of a season. Because annual variation in catch is presumed to be due to a combination of prevailing environmental conditions, fishing effort, price and relative abundance of shrimp (SAFMC 1996b), fishing is not believed to have any impact on subsequent year class strength unless the spawning stock has been reduced below a minimum threshold level by environmental conditions. Nevertheless, due to high fecundity and migratory behavior, the three penaeid species are capable of rebounding from very low population sizes in one year to large population sizes in the next, provided environmental conditions are favorable (SAFMC 1996b).

Fluctuations in abundance resulting from changes in environmental conditions will continue to occur. Perhaps the most serious potential threat to the stocks is loss of habitat due to pollution or physical alteration. For white and brown shrimp, salt marsh habitat is especially important as juvenile nursery areas. Inshore seagrass beds are important nursery areas for juvenile pink shrimp. The quality and availability of these habitat areas to the juvenile penaeid shrimp species is critical to overall shrimp production (SAFMC 1996b).

During years when inshore overwintering white shrimp stocks are greatly reduced due to cold water temperature or heavy rain, management action may accelerate recovery of the stocks and increase fall production by protecting the few remaining spawners that survive a freeze. Also, elimination of winter and spring fishing mortality off southern Georgia and Florida may enable a greater quantity of potential spawners to move north, possibly resulting in larger regional white shrimp stocks the following fall. An offshore or deep estuarine water reserve of overwintering white shrimp may also contribute significantly to the spawning stock. In either case, while fishing does not by itself appear to be a factor in determining subsequent year class strength for white shrimp, in years when the overwintering adult population is significantly reduced due to severe winter weather, the additional mortality caused by fishing can result in a further reduction in subsequent fall production (SAFMC 1996b).

(from Shrimp Amendment 6) For the South Atlantic shrimp fishery, only historical catch records and limited effort information is available. Current data gaps preclude the estimation of BMSY. Furthermore, because of high fluctuations in annual recruitment and landings, FMSY, or even FCURR, cannot be estimated. This limited information makes it difficult to use standard procedures to establish an overfishing threshold based on FMSY. Nevertheless, the Council has stated, that although estimates of population size are not available, effort in the fishery is known to be high and the fishery may be fishing at near-maximum levels. Therefore, it can be assumed to be operating at or near BMSY and FMSY. Based on that assumption, the Council has established targets and thresholds using annual landings as an indication of relative abundance (health) of the parent stock.

The limitation to this approach, especially for annual species such as shrimp, is its total dependence on catch, without accounting for external factors such as economic or social conditions that might influence the overall annual landings of a particular species. It is possible that the fishery might not target a species to the extent possible during a given year, and low landings could result from a lack of effort instead of a reduced stock size. Similarly, a stock might undergo a poor recruitment year, but still be relatively healthy, but reduced catch rates combined with economic or social factors might inhibit fishery effort on that stock, and annual landings would decline. Conversely, because of good prices or exceptionally good recruitment, landings might be exceptionally high during a given year, or two-year period. In either situation, the Council would want to further evaluate all the conditions before making a determination regarding the status of the stock, which could delay effective remedial action.

The National Standard Guidelines (50 CFR 600.310[c][2][i]) identify alternatives for establishing MSY to include removal of a constant catch each year that allows the stock size to remain above an identified lower level, or to allow a constant level of parent stock escapement each year. For penaeid shrimp stocks, it is appropriate to establish an MSY control rule based on maintaining a constant level of escapement each year that will produce sufficient recruits to maintain harvest at historical levels. This approach would relate MSY in terms of catch to a quantifiable level of escapement in each stock, where a proxy for BMSY is established as the minimum parent stock size known to have produced MSY the following year. MFMT, as a fishing mortality that drives the stock below BMSY in a given year when exceeded, would define overfishing. MSST, or the overfished level, would represent a biomass level lower than 0.5*BMSY (i.e., one-half the parent stock size or other proxy). In other words, this would be an MSY control rule that relied on constant escapement of BMSY.

In accordance with the Technical Guidelines (Restrepo et al., 1998), CPUE data can be used as a proxy for biomass-based parameters including BMSY and current biomass. Until those data become available from the fishery, CPUE-based abundance estimates from fishery-independent Southeast Area Monitoring and Assessment Program - South Atlantic (SEAMAP-SA) data can serve as a proxy to indicate parent stock (escapement).

The SEAMAP-SA Shallow Water Trawl Survey is funded by NOAA Fisheries and conducted by the South Carolina Department of Natural Resources - Marine Resources Division (SCDNR- MRD). This survey provides long-term, fishery-independent data on seasonal abundance and biomass of all finfish, elasmobranchs, decapod and stomatopod , sea turtles, horseshoe crabs and cephalopods that are accessible by high-rise trawls. Samples are taken by trawl from Cape Hatteras, North Carolina to Cape Canaveral, Florida. Cruises are conducted in spring (early April - mid-May), summer (mid-July - early August) and fall (October - mid- November). Stations are randomly selected from a pool of stations within each stratum. Strata are delineated by the 4 m depth contour inshore and the 10 m depth contour offshore.

SEAMAP data for the period 1990-1992 indicate that the average escapement results in annual abundance estimates ranging from 1.975 to 10.277 shrimp per hectare for brown shrimp, 0.211 to 1.728 shrimp per hectare for pink shrimp and 5.665 to 34.799 shrimp per hectare for white shrimp (Table 4.1-1).

Table 4.1-1. Annual shrimp CPUE (nos/ha) estimates derived from the SEAMAP Shallow water Trawl Survey. Year Brown Shrimp Pink Shrimp White Shrimp 1990 4.022 0.568 9.028 1991 2.469 0.873 12.880 1992 2.000 0.511 5.868 1993 5.899 0.673 5.665 1994 5.568 0.594 10.606 1995 3.104 1.728 17.535 1996 10.277 0.461 12.913 1997 2.275 0.948 7.447 1998 1.975 0.853 18.256 1999 2.972 0.450 34.799 2000 7.697 0.211 13.060 2001 8.637 0.502 10.454 2002 3.347 0.867 9.186 2003 9.640 0.418 7.372

Because of their high sensitivity to certain environmental factors, South Atlantic shrimp show extreme fluctuations in population size. Annual sampling of shrimp from the southeast region indicate that density per hectare have varied by a factor of 5 to 10 and can more than double from one year to the next (Table 4.1-1).

The current stock status determination criteria for white, brown and pink shrimp were calculated from landings information. The data used to generate these parameters are presented in Table 4.1-2. These landings statistics were compiled in the original plan and Amendment 2 to the South Atlantic Shrimp Plan (SAFMC 1993; SAFMC 1996b).

Table 4.1-2. Landings data used to calculate the current MSY values for the penaeid species in the South Atlantic. (SAFMC 1996b).

Year White Shrimp Brown Shrimp Pink Shrimp 1957 14,712,461 9,740,164 2,157,243 1958 11,092,893 9,189,603 823,467 1959 12,823,217 9,434,893 2,061,216 1960 18,788,016 9,038,236 1,226,496 1961 14,033,378 2,495,614 1,747,822 1962 12,133,840 11,532,694 2,246,510 1963 7,268,926 7,646,291 554,339 1964 8,119,217 7,089,616 1,948,048 1965 16,304,005 8,126,345 1,687,237 1966 9,162,164 11,604,450 531,230 1967 10,902,104 7,978,838 1,579,998 1968 16,945,887 5,919,510 1,337,930 1969 16,914,732 8,570,168 1,698,021 1970 12,491,819 7,133,124 860,584 1971 18,810,304 9,764,458 1,914,656 1972 16,635,560 7,725,422 788,277 1973 18,241,500 4,502,900 1,518,395 1974 13,375,345 11,088,656 2,118,261 1975 15,910,990 6,713,349 2,015,874 1976 14,370,316 9,651,432 1,815,048 1977 4,961,115 10,605,268 801,227 1978 8,913,478 6,601,646 561,297 1979 17,014,249 6,643,381 1,775,764 1980 14,255,717 13,368,442 1,573,926 1981 8,367,526 4,372,667 871,121 1982 10,517,276 8,915,451 1,749,785 1983 12,404,793 6,711,871 2,699,625 1984 4,088,105 7,209,256 1,391,292 1985 7,727,811 16,318,704 1,438,953 1986 10,968,861 8,702,924 2,101,628 1987 13,086,952 3,024,169 3,139,447 1988 10,909,691 8,143,448 2,929,585 1989 13,851,605 9,231,743 3,393,081 1990 12,613,723 8,734,294 1,651,188 1991 18,272,539 10,680,481 2,699,144

White shrimp Maximum Sustainable Yield The existing definition of MSY established by the original Shrimp Plan was calculated as mean total landings for the South Atlantic during 1957 to 1991 adjusted for recreational landings. In calculating total landings, an additional ten percent (an estimate made by state shrimp biologists) was added to the commercial catch to account for recreational landings that were unreported. There were other adjustments based on more accurate recreational landings information when the shrimp baiting permit went into effect in South Carolina. Using this methodology, MSY is estimated to be 14.5 million pounds for white shrimp (SAFMC 1993).

Optimum Yield OY for the white shrimp fishery is defined as the amount of harvest that can be taken by U.S. fishermen without reducing the spawning stock below the level necessary to ensure adequate reproduction. This level has been estimated only for the central coastal area of South Carolina, and only in terms of subsequent fall production (assumed to represent recruitment). Therefore, in actual application, OY for the white shrimp fishery is the amount of harvest that can be taken by the U.S. fishery during the fishing season which may vary from year to year based on both state regulations and regulations promulgated pursuant to the Shrimp FMP (i.e., closures due to cold kills) (SAFMC 1993).

Overfished Definition The Council has not established an overfished definition for white shrimp. Nevertheless, the overfishing definition, indicating when population sizes have declined below a minimum threshold would also represent an overfished definition.

Overfishing Definition Overfishing is indicated when the overwintering white shrimp population within a state’s waters declines by 80% or more following severe winter weather resulting in prolonged cold water temperatures. Continued fishing following such a decline may reduce the reproductive capacity of the stock affecting subsequent recruitment and would be considered overfishing. Relative population abundance will be determined by catch per unit effort (CPUE) during standardized assessment sampling (SAFMC 1993).

Brown shrimp Maximum Sustainable Yield The existing definition of MSY established by the original Shrimp Plan was calculated as the mean total landings for the South Atlantic during 1957 to 1991 adjusted for recreational landings. In calculating total landings, an additional ten percent (an estimate provided by state shrimp biologists) was added to the commercial catch to account for recreational landings that are unreported. Using this methodology, MSY was estimated to be 9.2 million pounds for brown shrimp (SAFMC 1993).

Optimum Yield OY for brown shrimp was defined in Amendment 2 to the Shrimp Plan as the amount of harvest that can be taken by U.S. fishermen without annual landings falling two standard deviations below the mean landings during 1957 through 1993 for three consecutive years (SAFMC 1996b). This value is 2,946,157 pounds (heads on).

Overfished Definition The South Atlantic brown shrimp resource is considered to be overfished when annual landings fall below two standard deviations below mean landings for the period 1957 to 1993 for three consecutive years (2,946,157 pounds (heads on)). The brown shrimp stocks in the South Atlantic are not considered overfished. Annual production appears to be most influenced by late winter and early spring environmental conditions as has been observed in the Gulf of Mexico (SAFMC 1996b).

Overfishing Definition The Council has not established an overfishing definition for brown shrimp. If landings fall below the overfished threshold, it can be assumed that overfishing is also occurring.

Pink shrimp Maximum Sustainable Yield The existing definition of MSY established by the original Shrimp Plan was calculated as mean total landings for the South Atlantic during 1957 to 1991 adjusted for recreational landings. In calculating total landings, an additional ten percent (an estimate provided by state shrimp biologists) was added to the commercial catch to account for recreational landings that are unreported. Using this methodology, MSY was estimated to be 1.8 million pounds for pink shrimp (SAFMC 1993).

Optimum Yield OY for pink shrimp was defined as the amount of harvest that can be taken by U.S. fishermen without annual landings falling two standard deviations below the mean landings during 1957 through 1993 for three consecutive years. This value is 286,293 pounds (heads on) for pink shrimp (SAFMC 1996b).

Overfished Definition The South Atlantic pink shrimp resource is overfished when annual landings fall below two standard deviations below mean landings during 1957 to 1993 for three consecutive years (286,293 pounds (heads on)). There are indications that pink shrimp abundance may be reduced by prolonged cold water conditions. However, unlike with white shrimp, there does not appear to be a biological justification for closing the fishery following cold kills. It is believed that overwintering shrimp that are not harvested before reaching the ocean may simply be lost to the fishery. Further, being at the northern end of their range, larvae produced by overwintering North Carolina pink shrimp may be carried north by prevailing currents and lost to the system (SAFMC 1993).

Overfishing Definition The Council has not established an overfishing definition for pink shrimp. If landings fall below the overfished threshold, it can be assumed that overfishing is also occurring.

4.1.1.2 Deepwater Shrimp

Description and distribution Rock Shrimp Rock shrimp, Sicyonia brevirostris, (Figure 4.1-5) are very different in appearance from the three penaeid species. Rock shrimp can be easily separated from penaeid species by their thick, rigid, stony exoskeleton. The body of the rock shrimp is covered with short hair and the abdomen has deep transverse grooves and numerous tubercles.

Figure 4.1-5. Rock shrimp, Sicyonia brevirostris.

Recruitment to the area offshore of Cape Canaveral occurs between April and August with two or more influxes of recruits entering within one season (Kennedy et al. 1977). Keiser (1976) described the distribution of rock shrimp in coastal waters of the southeastern . Whitaker (1982) presented a summary of information on rock shrimp off South Carolina. The only comprehensive research to date on rock shrimp off the east coast of Florida was by Kennedy et al. (1977). This section presents some of the more significant findings by Kennedy et al. (1977) regarding the biology of rock shrimp on the east coast of Florida.

Rock shrimp are found in the Gulf of Mexico, Cuba, the Bahamas, and the Atlantic Coast of the U.S. up to Virginia (SAFMC, 1993). The center of abundance and the concentrated commercial fishery for rock shrimp in the south Atlantic region occurs off northeast Florida south to Jupiter Inlet. Rock shrimp live mainly on sand bottom from a few meters to 183 m (600 ft), occasionally deeper (SAFMC 1993). The largest concentrations are found between 25 and 65 m (82 and 213 ft).

Although rock shrimp are also found off North Carolina, South Carolina, and Georgia and are occasionally landed in these states, no sustainable commercially harvestable quantities of rock shrimp comparable to the fishery prosecuted in the EEZ off Florida are being exploited.

Royal Red Shrimp Royal red shrimp, Pleoticus robustus, (Figure 4.1-6) are members of the family Solenoceridae, and are characterized by a body covered with short hair and a rostrum with the ventral margin toothless. Color can range from orange to milky white. Royal red shrimp are found on the continental slope throughout the Gulf of Mexico and South Atlantic area from Cape Cod to French Guiana. In the South Atlantic they are found in large concentrations primarily off northeast Florida. They inhabit the upper regions of the continental slope from 180 m (590 ft) to about 730 m (2,395 ft), but concentrations are usually found at depths of between 250 m (820 ft) and 475 m (1,558 ft) over blue/black mud, sand, muddy sand, or white calcareous mud. Royal red shrimp are not burrowers but dig grooves in the substrate in search of small benthic organisms (Carpenter 2002). They have been commercially harvested in a relatively limited capacity.

Figure 4.1-6. Royal red shrimp, Pleoticus robustus (Perez-Farfante and Kenlsey 1997)

Reproduction Rock Shrimp Rock shrimp are dioecious (separate sexes). Female rock shrimp attain sexual maturity at about 17 mm carapace length (CL), and all males are mature by 24 mm CL. Seasonal temperature initiates maturation. Rock shrimp have ovaries that extend from the anterior end of the cephalothorax to the posterior end of the abdomen.

Female rock shrimp attain sexual maturity at about 0.7 in (17 mm) carapace length (CL), and all males are mature by 0.9 in (24 mm) CL. Rock shrimp, as with most shrimp species, are highly fecund. Fecundity most probably, as with penaeids, increases with size. In rock shrimp, copulation is believed to take place between hard-shelled individuals. During copulation, similar to penaeid shrimp, the male anchors the spermatophore to the female’s thelycum by the petasma and other structures and a glutinous material. Fertilization is believed to take place as ova and spermatozoa are simultaneously expulsed from the female. The spawning season for rock shrimp is variable with peak spawning beginning between November and January and lasting 3 months (Kennedy et al. 1977). Individual females may spawn three or more times in one season. Peak spawning activity seems to occur monthly and coincides with the full moon (Kennedy et al. 1977).

Kennedy et al. (1977) found rock shrimp larvae to be present year round with no trend relative to depth, temperature, salinity, and length or moon phase. The development from egg to postlarvae takes approximately one month. Subsequently the development from postlarvae to the smallest mode of recruits takes two to three months.

Development, growth and movement patterns Rock Shrimp For rock shrimp the development from egg to postlarvae takes approximately one month. Subsequently, the development from postlarvae to the smallest mode of recruits takes two to three months. The major transport mechanism affecting planktonic larval rock shrimp is the shelf current systems near Cape Canaveral, Florida (Bumpus 1973). These currents keep larvae on the Florida Shelf and may transport them inshore during spring. Recruitment to the area offshore of Cape Canaveral occurs between April and August with two or more influxes of recruits entering within one season (Kennedy et al. 1977).

Rates of growth in rock shrimp are variable and depend on factors such as season, water temperature, shrimp density, size, and sex. Rock shrimp grow about 2 to 3 mm CL (0.08 – 0.1 in) per month as juveniles and 0.5 - 0.6 mm CL (0.02 in) per month as adults (Kennedy et al. 1977).

Density is thought to also affect growth of rock shrimp. In 1993, the industry indicated that rock shrimp were abundant but never grew significantly over 36/40 count that was the predominant size class harvested during July and August of that year. During years of low densities, the average size appears to be generally larger.

Since rock shrimp live between 20 and 22 months, natural mortality rates are very high, and with fishing, virtually the entire year class will be dead at the end of the season. The intense fishing effort that exists in today’s fishery, harvests exclusively the incoming year class. Three year classes were present in sampling conducted between 1973 and 1974 by Kennedy et al. (1977). Fishing mortality in combination with high natural mortality and possibly poor environmental conditions may be high enough to prevent any significant escapement of adults to constitute a harvestable segment of the population. The better than average rock shrimp production in the 1996 season possibly resulted from better environmental conditions more conducive to rock shrimp reproduction and spawning.

Ecological relationships Rock Shrimp Along the Florida Atlantic coast, the predominant substrate inside of 200 m depth is fine to medium sand with small patches of silt and clay (Milliman 1972). Juvenile and adult rock shrimp are bottom feeders. Rock shrimp are most active at night (Carpenter 2003). Stomach contents analyses indicated that rock shrimp primarily feed on small bivalve mollusks and decapod crustaceans (Cobb et al. 1973). Kennedy et al. (1977) found the relative abundance of particular crustaceans and mollusks in stomach contents of rock shrimp corresponding to their availability in the surrounding benthic habitat. The diet of Sicyonia brevirostris consists primarily of mollusks, crustaceans and polychaete worms. Also included are nematodes, and foraminiferans. Ostracods, amphipods and decapods made up the bulk of the diet, with lesser amounts of tanaidaceans, isopods, cumaceans, gastropods, and other bivalves also present (Kennedy et al. 1977).

Kennedy et al. (1977) characterized rock shrimp habitat and compiled a list of and molluscan taxa associated with rock shrimp benthic habitat. The bottom habitat on which rock shrimp thrive is limited and thus limits the depth distribution of these shrimp. Cobb et al. (1973) found the inshore distribution of rock shrimp to be associated with terrigenous and biogenic sand substrates and only sporadically on mud. Rock shrimp also utilize hardbottom and coral, more specifically Oculina, habitat areas. This was confirmed with research trawls capturing large amounts of rock shrimp in and around the Oculina Bank HAPC prior to its designation.

Abundance and status of stocks Rock Shrimp (from Shrimp Amendment 6) For stocks such as rock shrimp information from which to establish stock status determination criteria are limited to measures of catch. Nevertheless, with the development of a permitting system and reporting requirements associated with the permit, better information will be collected on the effort and catch in this fishery. Data should be reviewed periodically to determine if better inferences can be drawn to address BMSY. Additionally, any time that annual catch levels trigger one of the selected thresholds, new effort should be made to infer BMSY or a reasonable proxy.

The current stock status determination criteria for rock shrimp were calculated from catch estimates as reported in Amendment 1 of the Shrimp Plan (SAFMC 1996a) during the period 1984-1996 (Table 4.1-3).

Table 4.1-3. Landings data used to calculate the current MSY value for rock shrimp in the South Atlantic. Year Landings 1986 2,514,895 1987 3,223,692 1988 1,933,097 1989 3,964,942 1990 3,507,955 1991 1,330,919 1992 2,572,727 1993 5,297,197 1994 6,714,761 Note: Data for the period 1986 to 1994 are taken from Shrimp Amendment 1 (SAFMC 1996a).

Maximum Sustainable Yield Because rock shrimp live only 20 to 22 months, landings fluctuate considerably from year to year depending primarily on environmental factors. Although there is a good historical time series of catch data, the associated effort data were not considered adequate to calculate a biologically realistic value for MSY. Nevertheless, two standard deviations above the mean total landings was considered to be a reasonable proxy for MSY (SAFMC 1996a). The MSY proxy for rock shrimp, based on the state data from 1986 to 1994, is 6,829,449 pounds heads on (SAFMC 1996a).

Optimum Yield OY is equal to MSY. The intent is to allow the amount of harvest that can be taken by U.S. fishermen without reducing the spawning stock below the level necessary to ensure adequate reproduction. This is appropriate for an annual crop like rock shrimp when recruitment is dependent on environmental conditions rather than female biomass. A relatively small number of mature shrimp can provide sufficient recruits for the subsequent year’s production (SAFMC 1996a).

Overfished Definition The South Atlantic rock shrimp resource is overfished when annual landings exceed a value two standard deviations above mean landings during 1986 to 1994 (mean=3,451,132 lb., s.d. =1,689,159), or 6,829,449 pounds heads on (SAFMC 1996a). In other words, the stock would be overfished if landings exceeded MSY. The status of rock shrimp stocks in the South Atlantic are not considered overfished at this time. High fecundity enables rock shrimp to rebound from a very low population size in one year to a high population size in the next when environmental conditions are favorable (SAFMC 1996a).

Overfishing Definition There is no designation of overfishing for rock shrimp. The overfished definition, which is based on landings (and fishing effort) in excess of average catch is, in essence, an overfishing definition.