(DRAFT) - Taxonomy
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
TAXONOMY
NAME - croaker, Atlantic
OTHER COMMON NAMES - croaker, croakus, hardhead, king billy and la corbina
ELEMENT CODE - 03/11/87
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - Chordata,
CLASS AND SUBCLASS - Osteichthyes,
ORDER AND SUBORDER - Perciformes,
FAMILY AND SUBFAMILY - Sciaenidae,
GENUS AND SUBGENUS - Micropogonias,
SPECIES AND SSP - undulatus,
SCIENTIFIC NAME - Micropogonias undulatus
AUTHORITY - Linnaeus
TAXONOMY REFERENCES - 3682 and 128
COMMENTS ON TAXONOMY -
Other common names include croaker, crocus, hardhead, King Billy, la corbina
*128*. The genus was changed from Micropogon *128*.
Taxonomy - 1 (DRAFT) - Status
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
See Comments
REFERENCES FOR STATUS - 128
COMMENTS ON STATUS -
The Atlantic croaker is one of several sciaenid fishes in coastal Gulf of
Mexico waters that are subject to significant commercial and sport
fisheries. It is the target species of an industrial groundfish fishery and
is often dominant in inshore and offshore sport catches. The species is
considered estuarine dependent as all stages from larvae to adults are known
to occur in abundance in estuarine waters. Postlarvae and juveniles grow
rapidly in estuarine nursery grounds and are subject to predation by several
other species. Although quantitative information is lacking, it is likely
that croakers play a significant role in estuarine trophic dynamics.*128*
Status - 1 (DRAFT) - Distribution
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - Aquatic
REFERENCES FOR HABITAT - 3682
LAND USE -
Water
Bays and Estuaries
REFERENCES FOR LAND USE - 3682
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine, subtidal UB2 L 2
Marine, subtidal UB3 L 2
Marine, subtidal RF2 L 2
Estuarine, subtidal UB2 L 2
Estuarine, subtidal UB3 L 2
Estuarine, subtidal UB2 L 3
Estuarine, subtidal UB3 L 3
Estuarine, subtidal UB2 L 4
Estuarine, subtidal UB3 L 4
Estuarine, subtidal UB3 L 5
Estuarine, subtidal UB3 L 6
Estuarine, subtidal UB2 L 7
Estuarine, subtidal UB3 L 7
REFERENCES FOR NWI - 3682
Habitat Associations - 1 HABITAT SUITABILITY MODELS -
V1 estuarine: turbidity 10-15 cm above the bottom, measured during spring or
summer as either suspended solids or JTU: maximum > 80 mq/l or > 5 JTU; minimum
0 mq/l or < 1 JTU; optimum > 80 mq/l or > 5 mq/l
V1 estuarine (optional to above) turbidity 1 m above the bottom, estimated
during spring or summer from water clearness/color: maximum dark brown or
opaque; minimum clear; optimum dark brown or opaque
V2 estuarine: minimum dissolved oxygen level 10 or 15 cm above the bottom
during spring or summer: maximum > 8 mq/l; minimum 2 mq/l; optimum > 6 mq/l
V3 estuarine: average salinity 10-15 cm above the bottom during spring or
summer: maximum > 20 ppt; minimum 0 ppt; optimum 2.5-10 ppt
V4 estuarine: rate of salinity change per hour, disregarding the sign of the
difference, 10-5 cm above the bottom during spring or summer, collect data at
least over half a tidal cycle: maximum 9 ppt/hr; minimum 0 ppt/hr; optimum 0-3
ppt/hr
V5 estuarine: temperature variance over 24 hr. 10-15 cm above the bottom,
subtract the highest temperature from the lowest temperature for 24 hr. period,
disregarding the sign of the difference: maximum 17 C; minimum 0 C; optimum
0-6 C
V6 estuarine (option A): ratio of marsh area to tidal creek area for Gulf of
Mexico coast or marsh-dominated areas: maximum > 10:1; minimum < 1:10; optimum
1:1
V6 estuarine (option B): ratio of bottom area deeper than 6 ft. mean low water
to total bottom area for Atlantic coast or water-dominated areas: maximum >
10:1; minimum 1:10; optimum > 1:1
V7 estuarine: dominate substrate type: least preferred mostly rock, no soft
material; optimum > 75% mud or silt, some sand or other material
V8 estuarine: percent organic matter or volatile solids in top 5 cm of sediment:
maximum > 20%; minimum 3%; optimum > 10% *03*
COMMENTS ON HABITAT SUITABILITY MODELS -
Model is not applicable in conditions where partial or extensive reduction in
habitat availability occurred as a result of toxic waste *03*; this model
pertains only to the juvenile atlantic croaker *03*; Assumptions of model: V1
high turbidity levels are positively related to croaker abundance; V2 low
levels of dissolved organic are not suitable; V3 the range of optimal salinity
is much narrower than the maximum range, and oligohaline and lower meso- haline
salinities are optimum; V4 high salinity stability is optimum, increasing
fluctuations decreased suitability; V5 high temperature stability is optimal,
increasing fluctuations decrease suitability; V6 (option A) optimal cover
diversity of marsh and tidal creek is found when approximately equal amounts of
both are present; V6 (option B) optimal cover is found when all bottom is
deeper than 6 ft. MLW; V7 soft mud is most suitable, sandy mud is less
suitable, hard and sandy substrates are unsuitable; V8 highly organic muds are
optimal *03*
REFERENCES FOR HABITAT SUITABILITY MODELS - 03
Habitat Associations - 2 (DRAFT) - Food Habits
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
FOOD HABITS
TROPHIC LEVEL -
OMNIVORE
REFERENCES FOR TROPHIC LEVEL - 128
LIFESTAGE FOOD FOOD PART
General See Comments; Food See Comments
Larva See Comments; Food See Comments
Juvenile See Comments; Food See Comments
COMMENTS ON FOOD -
The Atlantic croaker as a species cannot be assigned to a single trophic
level, as dietary shifts occur during their lifetime (Darnell 1958,
1961). Darnell (1958) described four active feeding stages, but later
(Darnell 1961) presented only three. While feeding habits between these
stages may be fairly distinct, feeding within stages is apparently rather
non-selective (Parker 1971).
No information was found on the duration of the yolk sac stage or
whether or not active feeding begins during or only after this stage.
Larval and postlarval croakers are largely zooplanktivorous and may be
considered secondary consumers. Several authors have reported detritus to
be a major component of the juvenile diet (Darnell 1961; Parker 1971; Etzold
and Christmas 1979). It is possible that croakers may play a minor role as
primary consumers, but it is not clear that ingested plant material (whether
discrete or detrital) is assimilated. Other than the initial
zooplanktivorous stage, all sizes of croakers are reported to ingest benthic
microinvertebrates. This is consistent with the observations of Roelofs
(1954), who found that croakers "dived deeply into the bottom with some
force, digging as they fed, and thus were able to obtain subsurface
material." Adults appear to feed similarly to juveniles, but are also
capable of taking larger invertebrates and fishes. As juvenile and adult,
therefore, the croaker may operate as a secondary, tertiary, or higher level
consumer. The importance of each of the various feeding stages of croakers
as consumers depends upon their number and rate of ingestion. No
quantitative study of the role of croakers in estuarine trophic dynamics was
found in the literature.*128*
At a community interaction level, croakers have been recorded as prey for
larger fishes including larger adults of their own species (Pearson 1929;
Gowenlach 1933), but again the quantitative importance of the croaker as a
prey item is not known. Parker (1971) concluded from diet and
distributional overlap data that "spot and croaker were found to be in
direct competition." There is, however, no experimental evidence to
support such a conclusion, and the use of overlap data to infer competition
is clearly insufficient and open to misinterpretation (Colwell and Futuyuma
1971).
Food Habits - 1 (DRAFT) - Environment Associations
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Turbidity: Murky water [High turbidity]
G Dissolved Oxygen: Moderate [5-7 mg/l] oxygen concentrations
G Substrate: Mud or silt
G Bottom Type [Aquatic]: Mud or silt
G Stability of Bottom: Unstable
G Water Depth Preference: 5-10 ft.
G Bottom Type [Aquatic]: Organic debris
G Bottom Type [Aquatic]: Sand
G Bottom Type [Aquatic]: Specified in Comments
G Water Depth Preference: 10-25 ft.
G Water Depth Preference: 25-50 ft.
G Water Depth Preference: 50-100 ft.
G Water Depth Preference: 100-200 ft.
G Water Temperature: Greater than 27 degrees C
G Water Temperature: Between 21-27 degrees C
G Water Temperature: Between 15-21 degrees C
G Water Temperature: Below 15 degrees C
LIM Turbidity: Clear water
LIM Dissolved Oxygen: Specified in Comments
RL Water Temperature: Between 21-27 degrees C
RL Water Temperature: Between 15-21 degrees C
RL Water Temperature: Below 15 degrees C
FJ Bottom Type [Aquatic]: Mud or silt
FJ Water Temperature: Specified in Comments
FJ Biodegradable Organics: Specified in Comments
RJ Bottom Type [Aquatic]: Mud or silt
RJ Bottom Type [Aquatic]: Organic debris
RJ Water Depth Preference: Specified in Comments
RJ Water Temperature: Greater than 27 degrees C
RJ Water Temperature: Between 21-27 degrees C
RJ Water Temperature: Between 15-21 degrees C
RJ Water Temperature: Below 15 degrees C
REFERENCES FOR ENVIRONMENTAL ASSOC_ - and 3682
REFERENCES FOR RESTING JUVENILE ENVIRONMENTAL ASSOC_ - 3682
REFERENCES FOR RESTING LARVAE ENVIRONMENTAL ASSOC_ - 3682
Environment Associations - 1 (DRAFT) - Environment Associations
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
Temperature
Rising temperatures (16 degrees C. or more) may induce immigration inshore
during spring.
Field and laboratory data both indicate that juveniles are more
tolerant of lower temperatures than adults. Parker (1971) reported that
juveniles have been taken in waters from 0.4 degrees to 35.5 degrees C. as
compared to 5 degrees to 35.5 degrees C for adults. Laboratory tests
established lower and upper lethal temperatures of 0.6 degrees and 38
degrees C. for juveniles andd 3.3 degrees and 36 degrees C for adults,
respectively. Sudden and prolonged cold snaps which occur while the
croakers still inhabit the shallower estuarine areas can cause mass
mortalities (Hildebrand and Cable 1930; Gunter andd Hildebrand 1951).
Parker (1971) found the highest abundances of croakers in waters from 21
degrees to 25 degrees C, but stated that "most months, appeared to be
rather evenly distributed over the range of available temperatures" except
that older fish (over 1 year old) were largely absent in waters below 10
degrees C.*128*
Salinity
Croakers have been collected in waters from very dilute (0.2 ppt) to
hypersaline (75 ppt) (Simmons 1957; Parker 1971). The survivorship of
croakers at the upper end of this range is unknown and occurrence in such
waters is uncommon. Parker (1971) stated that "the nature of the life
history of the Atlantic croaker requires that postlarvae and juveniles be
adaptive, not only to a compartively broad salinity range, but also to
relatively rapid salinity changes." *128*
00110S= 'live'bottoms of coral and sponge *3682*
00200S= salinities from 0-40 ppt., more abundant at higher salinities *3682*
COMMENTS ON RESTING JUVENILE ENVIRONMENTAL ASSOC_ -
00220S= taken in salinities from 0-36.7 ppt *3682*
00290S= confined to bottom waters of relatively deep channels *3682*
COMMENTS ON RESTING LARVAE ENVIRONMENTAL ASSOC_ -
00220S= salinities from 0-21 ppt. *3682*
COMMENTS ON FEEDING LARVAE ENVIRONMENTAL ASSOC_ -
Postlarvae were taken in waters from 6 degrees to 20 degrees C but a wider
tolerance range was suspected.*128*
Environment Associations - 2 (DRAFT) - Life History
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
LIFE HISTORY
Physical Description
Body elongate, compressed; back moderately elevated; head rather long;
snout conical, projecting beyond the mouth in the adult and proportionately
much longer than in the very young, 2.85 to 3.75 in head; eye 3.35 to 4.8;
interorbital 3.35 to 3.8; mouth moderate, horizontal, inferior; maxillary
reaching a little past front of eye to below middle of eye, 2.3 to 2.85 in
head; teeth in the jaws all small, in broad villiform bands; chin with
several pores and a row of short. slender barbels on each side; preopercle
with strong, short spines on margin; gill rakers short; scales moderate,
reduced anteriorly above lateral line, strongly ctenoid, extending on the
caudal but not on the other fins; dorsal fins contiguous, or more or less
continuous in young, the first composed of slender spines, somewhat
elevated, the third and fourth spines longest, higher than any of the rays
in the soft part; caudal fin slightly double concave in adult, with the
upper and middle rays longest, sharply pointed in very young; anal fin
small, with two strong spines, the first very short, the second about
two-thirds the length of the soft rays; ventral fins moderate, inserted
under and slightly behind base of pectorals; pectorals rather long in adult,
reaching well beyond tips of ventrals in young, 1.15 to 1.5 in head.
Color in life: greenish or grayish silvery to brassy yellowish and
highly irridescent above, silvery white below; back and sides with many
brassy or brownish short, irregular, oblique bars formed by spots on scales.
Bars may become less distinct in larger adults. Young usually paler,
silvery. Larval and postlarval forms are described by Pearson (1929).*128*
Spawning
Spawning by the Atlantic croaker has never been observed. The site and
time of spawning are therefore inferred from the capture of ripe adults
or early development stages. Most published works agree with the early work
of Pearson (1929), who suggested that spawning occurs in the open gulf "near
the mouths of the various passes that lead into the shallow bays and
lagoons." Bearden (1964), however, maintained that croakers along the South
Carolina coast spawn entirely in the ocean as he found ripe females as far
as 48 km (30mi) offshore. Hildebrand and Cable (1930) also reported taking
very young croakers 24 km (15mi) offshore. Spawning is reported to occur
within a depth range of 7.8 to 81 m or 26 to 266 ft. (Fruge and Truesdale,
1978).
The Atlantic croaker, as with other sciaenids, has a protracted spawning
season. Within its entire range, larval and postlarval stages have been
collected in passes and bays from as early as August in Chesapeake Bay
(Hildebrand and Schroeder, 1928) to as late as June in Louisiana (Suttkus
1955). For a female of 395 mm total length (TL)3, Hildebrand and Cable
(1930) reported 180,000 uniform size eggs, but Hansen (1970) reported only
41,200 eggs. No explanation for this disparity has been found. Eggs are
pelagic and hatch in less than 1 week (Hildebrand and Cable 1930; Gutherz
1976).*128*
Larval Stage
Life History - 1 (DRAFT) - Life History
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
After hatching, larvae and post-larvae may spend some time in the
plankton (Hildebrand and Cable 1930), but apparently soon become demersal
(Hildebrand and Cable 1930; Fruge and Truesdale 1978). A demersal habit
would concur with Pearson's (1929) observation that larvae were caught
primarily in the deeper waters of the passes. It is unclear whether the
movement of larvae into the estuaries is passive or active or a function of
both. Perkins (1974) stated that "the reaction current may carry the newly
hatched fish over 100 miles upstream to the upper limits of the saltwater
intrusion.... this first movement is passive." However, Pearson's (1929)
observations of postlarval croakers suggest that the movement is, at least
in part, an active process. He stated, "A determined attempt... to gain
the shelter of the bays was observed on many occassions. Few fish could
breast the strong current of the ebb tide, but the young croakers, massed in
schools, were seen attempting to enter the passes by hugging the sides of
the channels and to take advantage of the slower currents. This schooling
behavior is maintained throughout life.*128*
Postlarvae and Juveniles
Once in the estuaries, the post-larvae and very young spread throughout
with heaviest concentrations at the headwaters (Pearson 1929; Gunther 1938;
Parker 1971). Young croakers remain in estuarine nursery areas at least
through spring and early summer before migrating to the gulf waters. It has
been suggested that emigration may begin as early as April (Texas) or June
(Louisiana) with the attainment of 60 to 85 mm TL. The significance of
these lengths, however, was not discussed, and later in this same report he
stated that peak gulfward migration in Louisiana occurs from September to
November.
Seaward migrating young-of-the-year are subject to depletion by both
shrimp and groundfish fisheries (Pearson 1929; GMFMC 1981) operating in
the open gulf waters. A single, very tentatively suggested estimate of
instantaneous fishing mortality (F) is given by GMFMC (1981) as 1.0, or an
annual expectation of death due to fishing of 63%. However, no comparison
of F with instantaneous natural maturity (M) was found in the
literature.*128*
Maturity and Life-Span
Most authors maintain that croakers mature at the end of their second
year (Pearson 1929; Gunter 1945; Johnson 1978), but others report that some
may mature and spawn before their second year is completed (Avault et. at.
1969; Hansen 1970; Etzold and Christmas 1979). Wallace (1940) reported that
males mature at 2 years and females at 3 years of age. Surviving spawners
and juveniles (by then the 1+ Yr-class) overwinter in the gulf and return to
the estuaries the following spring. The cycle may repeat several times
during the lifetime of a single fish, as at least some members of the
species live to 4 to 5 years of age but rarely greater (Parker 1971; Etzold
and Christmas 1979).
No one has suggested that this species dies after spawning, and there
have been no reported observations of massive numbers of spent Atlantic
croaker carcasses (e.g., in trawls, along shore) as is common for salmonid
and osmerid species of more temperate waters. However, from earlist authors
there has been the hint of high post-spawning mortality. Pearson (1929)
Life History - 2 (DRAFT) - Life History
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
reported that after spawning in the fall of their second year, croakers
"return in small numbers" and that it "may be that most croakers die after
spawning." This observation is echoed by Gunter (1938), Parker (1971), and
others. It is possible that this observation may simply be a false
impression resulting from a normally high natural mortality or high
overwinter fishing mortality or both. As mentioned above, however, almost
no information exists on mortality or on the percentage of returning
spawners.*128*
REFERENCES FOR LIFE HISTORY- 128
Life History - 3 (DRAFT) - Management Practices
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
MANAGEMENT PRACTICES
Management Practices - 1 (DRAFT) - References
Species croaker, Atlantic
Species Id M010250
Date 27 AUG 96
References
3682* Johnson, G.D. 1978. Development of fishes of the
Mid-Atlantic Bight. Volume IV. Carangidae through Ephippdae IV.
U.S. Fish and Wildl. Ser.
128* Lassuy, D. 1983. Species Profiles: Life Histories and
Environmental Requirements (Gulf of Mexico) -- Atlantic Croaker.
U.S. Fish and Wildlife Service Biol. Rep. 82(11.3) pp 12.
References - 1