||Leiostomus xanthurus Lacepede, 1803
Other Taxonomic Groupings
Leiostomus xanthurus is a moderately deep-bodied, compressed fish with an elevated back.
Body color is typically bluish-gray dorsally, fading to golden yellow or
yellow-tan ventrally. A set of 12 -15 dark streaks run obliquely from the
dorsal surface down the sides to about mid-body. These tend to fade with
age. Fins are typically pale yellow in color. The head is short, with a small,
inferior mouth. The maxilla extends to approximately the middle of the eye.
The dorsal fin is continuous, with a notch separating the spinous portion from
the soft rays. There are 9-11 dorsal spines, and 29-35 soft rays. The anal fin
has 2 spines and 12-13 rays. The caudal peduncle is moderately deep, and the
caudal fin is notched. A large black spot is set above the upper edge of the
gill cover. There are 72-77 lateral line scales (Johnson 1978).
Potentially Misidentified Species
Adults are not typically mistaken for other Sciaenids due to the prominent spot
and faint oblique stripes. However, juveniles resemble a number of related
species including the Atlantic croaker, Micropogonias undulatus and the
silver perch, Bairdiella chrysoura. The Atlantic croaker is
differentiated from the spot by having barbells on the lower jaw and a serrate
preopercule. The silver perch is differentiated by its rounded caudal fin and
well developed teeth.
HABITAT AND DISTRIBUTION
Leiostomus xanthurus is common along the Atlantic coast from Cape Cod south to the Bay of Campeche, Mexico. It occurs irregularly in south Florida and the Florida Keys, and north of Cape Cod, Massachusetts (Bigelow and Schroeder 1953; Chao 1978).
Spot are common throughout the Indian River Lagoon, especially around Brevard
and Indian River Counties.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Leiostomus xanthusrus grows to
approximately 11 inches total length (TL). In the first year it may reach 5.9
inches; in the second year, 8.7 inches; and in the third year 11 inches
(Townsend 1956; Welsh and Breder, 1923; McRae et al. 1997). The lifespan may
be as long as 5 years (DeVries 1982).
Growth rates in spot
show both seasonal and annual variation. In young juveniles, growth rates are
fastest in late spring and early summer, with high estuarine water temperatures
in late summer and early fall tending to reduce feeding and retarding growth
(Weinstein and Walters, 1981). Both juvenile and adult spot grow more slowly
during winter (Dawson, 1958).
Leiostomus xanthurus is one of the most common demersal fishes in coastal and estuarine
waters of the Atlantic, and has both
commercial and recreational importance. In some areas, the recreational catch
often exceeds the commercial harvest (Hales and Van Den Avyle 1989).
Larval spot have limited swimming abilities measured at 0.25 - 1.0 m/s for brief
periods (Lewis and Judy 1983). Adult spot have significantly slower swimming
speeds than other estuarine species (Hettler 1979), with a typical speed of
approximately 0.7 m/s (Rulifson 1977).
Spot Small spot (<2.7 cm
SL) are unable to orient in currents exceeding 15 cm/s. Larger spot, (to 5 cm
SL) cannot maintain orientation when currents exceed 30 cm/sec (Hales and Van
Den Avyle 1989).
Spot typically migrate offshore and spawn in the relatively deep water of the
outer continental shelf, though some evidently spawn in both nearshore waters
and estuaries (Dawson 1958; Lewis and Judy 1983). Ripe adults aggregate off
beaches in fall and begin migration offshore, possibly migrating to more
southern waters in the process (Pearson 1932). Spot may spawn repeatedly over
several weeks (Hildebrand and Cable 1930), with some individuals remaining
offshore after spawning (Pearson 1932; Wenner et al. 1979, 1980).
In the south Atlantic
region of the U.S., spawning occurs from October through March, peaking in
December and January (Townsend 1956; Lewis and Judy 1983; Warlen and Chester
1985). This is later than in mid-Atlantic waters and earlier than in the Gulf
of Mexico, where spawning begins in December and peaks in January and February
Most spot reach sexual
maturity in the second year, but some require 3 years (Hales and Van Den Avyle
1989). Dawson (1958) and Music (1974) reported that spot measuring 170 -175 mm
total length (TL) showed ripened gonads. However, other research (Hildebrand
and Cable 1930; Gunter 1945; Townsend 1956) suggests sexual maturity is
attained at somewhat larger size, between 185 - 210 mm TL. Music (1974)
reported that males may reach maturity at slightly smaller sizes than do
females, 170 mm TL for males vs. 205 mm TL for females.
Dawson (1958) estimated
fecundity for spot at approximately 77,000 - 84,000 eggs per season.
Eggs are pelagic and buoyant. Under laboratory conditions, eggs hatched at 20°C
within 24 hours. Larvae absorb the yolk sac and oil globule within 5 days of
hatching (Powell and Gordy 1980). Larvae are initially found in surface waters
but become more demersal as they grow (Hildebrand and Cable 1930; Lewis and
Judy 1983). Due to the limited swimming ability of larvae, it is believed that
passive mechanisms (wind, Ekman transport, tides) are the primary transporters
of larvae to the nursery habitats of estuaries and bays.
arrive at estuaries when they are approximately 10 - 24 mm Standard length (SL)
and 40 - 47 days old (Warlen and Chester 1985), typically in January (Hildebrand
and Cable 1983; Lewis and Judy 1983), with recruitment peaking in
February and March (Hildebrand and Cable 1983). Larvae continuing to enter
estuaries through June.
Postlarvae and smaller juveniles tend to congregate in shallow water areas of
tidal creeks in estuaries for 3-6 months (Weinstein and Walters 1981).
Thereafter, they tend to migrate to other estuarine habitats, and often migrate
to deeper waters (Weinstein 1983; Weinstein and Brooks 1983; Rojas and
and Chester (1985) examined growth characteristics of larvae and juveniles and
found that initial growth is rapid while larvae remain in offshore waters,
presumably due to the abundance of plankton available. Growth then slows in the
early period of estuarine residency, until approximately April. After
metamorphosis to the juvenile stage, growth is again accelerated.
Mass mortality of spot was observed at water temperatures of 5 - 10 °C, but
larvae and postlarvae may be more tolerant of widely ranging temperatures than
are older fish (Hildebrand and Cable 1930; Hodson et al. 1981a).
conditions (Hettler and Powell 1981) reported spawning occurred at 17-25°C.
Spot embryos do not develop at temperatures below 14°C; however, larvae can
tolerate temperatures as low as 5 °C. (Hettler and Clements 1978). Burton
(1979) reported symptoms of cold stress in juveniles held at 5°C.
Upper thermal tolerance
for postlarvae and juvenile spot is approx 35 °C, depending on the size and
general condition of fish, as well as the temperature the have been acclimated
to. Generally, as acclimation temperatures increase, the critical thermal
maximum also increases (Hodson et al. 1981a).
Low salinity does not appear to be necessary for proper development and
metamorphosis to the juvenile stage; however, it may affect survivorship of
larvae (Powell and Gordy 1980). Perez (1969) found that spot tended to be more
active under lab conditions when salinity changed quickly, suggesting that they
may actively try to avoid areas where salinity levels change rapidly.
Postlarval and juvenile spot have intermediate tolerance to hypoxic conditions
in comparison to other estuarine species (Burton et al 1980). Exposure of 90 mm
TL spot to 0.8mg/L for 96 hours resulted in 5% mortality; however, lowering the
concentration to 0.6 mg/L resulted in 95% mortality.
Leiostomus xanthurus show 2 distinct feeding modes: larvae are selective plankton feeders,
while juveniles and adults are partly olfactory-dependent, benthic feeders that
prey on infaunal and epibenthic invertebrates.
Preferred larval foods
include ciliates, invertebrate eggs, and copepod nauplii. Individuals up to 25
mm SL feed primarily on copepods and ostracods (Hildebrand and Cable 1930).
Upon metamorphosis, the diet changes to include insect larvae, polychaetes,
harpacticoid copepods and other crustaceans (Hildebrand and Cable 1930;
Townsend 1956; Hodson et al. 1981b); however, the juvenile diet can be
flexible and often is reflective of prey availability in specific areas (Hales
and Van Den Avyle 1989).
Chao and Musick (1977)
reported that in Chesapeake Bay, prey for adult spot includes zooplankton and
benthic infauna, with polychaetes most frequently observed in gut contents.
Other prey types included amohipods, cumaceans, gastropods, nematodes, mysids,
After growth to 10 - 15mm SL, larvae of all sizes feed diurnally (Govoni et al. 1983).
Spot likely compete with other estuarine species; however little research has
been undertaken in this area.
Spot are common in coastal waters during the spawning season, and in estuaries
and nearshore waters during other parts of the year. They are typically found
over sandy or muddy bottoms in waters up to approximately 60 m deep.
Postlarvae feed most actively during daylight hours, with peaks in late morning
(Kjelson et al. 1975). Juveniles switch to nocturnal feeding after
metamorphosis, perhaps as a predator avoidance mechanism, or to avoid high
daytime temperatures in shallow marshes (Hodson et al. 1981b). Adults tend to
Predators of spot include silversides (Menidia spp.), which may affect
postlarval distribution in estuaries (Weinstein and Walters 1981). Juveniles
and adult spot are also preyed upon by many fishes, including striped bass,
sharks, seatrout, bluefish, mackerels, gars, and flounders (Hollis 1952; Rozas
and Hackney 1984).
Parasites of spot include copepods of the genera Lernaeenicus and
Ergasilus, as well as a marine leech, Myzobdella lugubris (Sawyer et
al. 1975). Internal parasites include trematodes, microsporideans, and
acanthocephalans (Sprague and Hussey 1980; Govoni 1983).
In 2001, statewide landings in Florida were 352,786 pounds. Of this,
approximately 90% of the statewide landings were made on the Atlantic coast of
Florida; with the recreational fishery for spot accounting for 86% of the total
(Murphy 2003). Commercial landings on the Atlantic are generally
concentrated around Brevard, Indian River and Martin counties.
1995, the commercial fishery for spot relied almost exclusively on gill nets.
The ban on entangling nets enacted in late 1995 prompted a shift toward smaller
gear such as cast nets and haul seines. As reflected in the reduced commercial
landings since the rule went into effect, Florida's abolition of entangling gear
use in July 1995 almost eliminated the traditional commercial fishery for spot.
Reduced fishing pressure could result in higher and more stable recruitment in
the future (McRae 1997b).
Figure 1. Annual dollar value of the
commercial catch of spot to the 5-county area of the Indian
Figure 2. Total spot dollar value
and percentage by county for the years 1987 - 2001.
Table 1. Total dollar value of IRL spot, Leiostomus xanthurus between 1987 - 2001.
||Value to IRL
Table 2. By-county annual and cumulative percentages of the spot harvest for the years 1987-2001.
Table 3. By-county cumulative dollar value and percentage of total for the spot harvest from 1987 - 2001.
||To 200 Miles
Figure 3. Survey data for the spot recreational fishery showing the number of fishes harvested in East Florida waters from 1997 - 2004.
Figure 4. Summary of the spot recreational harvest and percentage of total by area from 1997 - 2004.
Table 4. Summary data for recreational fishery in Eastern Florida waters for the spot, Leiostomus xanthurus, from 1997 - 2004. Data provided by National Marine Fisheries Service, Fisheries Statistics Division, NOAA.
||To 3 Miles
||To 200 Miles
Table 5. By-county annual and cumulative percentages of the spot harvest for the years 1997 - 2001. Data provided by National Marine Fisheries Service, Fisheries Statistics Division, NOAA.
||To 200 Miles
Table 6. Summary of the spot recreational harvest and percentage of total fish captured in each area from 1997 - 2004. Data provided by National Marine Fisheries Service, Fisheries Statistics Division, NOAA.
||To 3 Miles
||To 200 Miles
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