(DRAFT) - Taxonomy
Species grunion, California
Species Id M010049
Date 27 AUG 96
TAXONOMY
NAME - grunion, California
OTHER COMMON NAMES - California grunion, grunion and smelt
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - Chordata,
CLASS AND SUBCLASS - Osteichthyes,
ORDER AND SUBORDER - Atheriniformes,
FAMILY AND SUBFAMILY - Atherinidae (Silversides),
GENUS AND SUBGENUS - Leuresthes,
SPECIES AND SSP - tenuis,
SCIENTIFIC NAME - Leuresthes tenuis
AUTHORITY - Ayres
TAXONOMY REFERENCES - 65
Taxonomy - 1 (DRAFT) - Status
Species grunion, California
Species Id M010049
Date 27 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Existing, FMP exists
Commercial/consumption
Commercial/bait
See Comments
REFERENCES FOR STATUS - 65
COMMENTS ON STATUS -
California grunion are caught by hand by sport fishermen during the open
season when the fish spawn on beaches above the surf line at night. The
commercial catch of grunion is taken incidentally while fishing for other
species and is marketed fresh as "smelt". Limited quantities are used for
live bait *65*.
From 1927 to 1946, the fishing season in California was closed from April to
June. Grunion may now be taken by sportsmen only by hand throughout the
year except in April and May *65*.
Status - 1 (DRAFT) - Distribution
Species grunion, California
Species Id M010049
Date 27 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
REFERENCES FOR HABITAT - 65
LAND USE -
Water
Bays and Estuaries
Beaches
REFERENCES FOR LAND USE - 65
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine BB. S
Marine BB. S
Marine BB2 S
Marine BB2 S
REFERENCES FOR NWI - 65
COMMENTS ON HABITAT ASSOCIATIONS -
The grunion has a unique spawning habit in that it spawns on land (on the
beach) *65*.
California grunion spawn every 4 weeks during the full moon tidal series.
Grunion begin spawning two to six nights after the peak tides of each
cycle, when each succeeding tide is lower than that of the previous night.
Only three or four nights are suitable for spawning during each cycle. The
spawning runs begin immediately after high tide *65*.
ANIMAL/PLANT SPECIES ASSOCIATIONS -
PARASITES:
PARASITES
Bomolachus pectinatus
Caligus olsoni
Clauellopsis
Argulus melanostictus
Nerocila californica
Lironeca californica
Metacercariae
Asymphylodora atherinopsidis
Lepocredium manteri
REFERENCES FOR SPECIES ASSOCIATIONS - 65
COMMENTS ON SPECIES ASSOCIATIONS -
PREDATION
All life stages of grunion are preyed upon by a number of predators. Eggs
buried in the beach sand are fed upon by sand worms, shore birds, and even
ground squirrels. Shorebirds such as marbled godwit and whimbrel actively
probe the sand in search of grunion eggs. An isopod, two species of flies,
and a beetle have also been reported to prey on buried grunion eggs.
Juvenile and adult grunion are preyed upon by halibut, sand bass, white
croakers, and other large predators, including man *65*.
PARASITES
The grunion is the host of several crustaceans and digenetic trematoes. The
six known crustacean parasites are the copepods Bomolachus pectinatus,
Habitat Associations - 1 Caligus olsoni, and Clauellopsis; the brachiuran Argulus melanostictus;
and the isopods Nerocila californica and Lironeca californica.
Metacercariae with the charactieristics of Bucephalopsis lebiatus Trematoda:
Bucephalida) infect the grunion heart muscle. Among the trematodes,
Asymphylodora atherinopsidis occurs in the posterior intestine of the
grunion while Lepocredium manteri occurs in the expanded anterior
intestine. The effects of these parasites on growth and survival are not
known *65*.
Habitat Associations - 2 (DRAFT) - Food Habits
Species grunion, California
Species Id M010049
Date 27 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 65
LIFESTAGE FOOD FOOD PART
Larva Protozoans
Larva Crustaceans Larva stage
Larva Copepods Larva stage
Adult Other (Specified in Comments) Not Applicable
Adult Zooplankton Not Applicable
Adult Microcrustaceans Not Applicable
REFERENCES FOR ADULT FOOD - 65
REFERENCES FOR LARVAE FOOD - 65
COMMENTS ON FOOD -
Gut content analysis indicates that grunion feed primarily during the day
*65*.
COMMENTS ON ADULT FOOD -
Adult grunion eat food similar to that eaten by larvae and juveniles.
Stomach contents consist of microscopic and slightly larger planktonic
organisms *65*.
COMMENTS ON LARVAE FOOD -
Food found in larvae less than 10 mm long consists largely of copepod
nauplii and tintinnid protozoans. Cyclopoid copepods, Oithona sp.,
numerically dominate the gut contents of larvae 10-28 mm long. The
harpactacoid copepod Euterpina acutifrons and the cyclopoid copepod
Corycaeus anglicus are much less abundant. The relatively low densities of
these animals in California's coastal waters suggest that most grunion
larvae must search for prey *65*.
Food Habits - 1 (DRAFT) - Environment Associations
Species grunion, California
Species Id M010049
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
LIM Water Temperature: Greater than 27 degrees C
LIM Water Temperature: Between 21-27 degrees C
LIM Water Temperature: Between 15-21 degrees C
LIM Water Temperature: Below 15 degrees C
LIM Water Temperature: Specified in Comments
LIM
BA Substrate: Sand
BA Substrate: Specified in Comments
BA Water Level: Specified in Comments
BA Coastal Features: Specified in Comments
BA Human Association: Specified in Comments
BA Tidal inundation frequency/ duration: specified in comments
E Water Temperature: Specified in Comments
E Substrate: Sand
E Substrate: Specified in Comments
E Water Level: Specified in Comments
E Coastal Features: Specified in Comments
E Tidal inundation frequency/ duration: specified in comments
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 65
REFERENCES FOR LIMITING ENVIRONMENTAL ASSOC_ - 65
REFERENCES FOR BREEDING ADULT ENVIRONMENTAL ASSOC_ - 65
REFERENCES FOR EGG ENVIRONMENTAL ASSOC_ - 65
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
Young grunion are positively phototactic and can be attracted to light as
bright as 10,000 lux. The strength of the gathering response is apparently
related to the strength of the light stimulus *65*.
COMMENTS ON LIMITING ENVIRONMENTAL ASSOC_ -
WATER TEMPERATURE
Water temperatures of 29.8 C and above reduce the viability of grunion
larvae *65*.
The ability of larvae to metabolize food (protein) decreases above
25 degrees C and below 16 degrees C (fat). Growth rates are positively
correlated with temperature between 18 degrees and 25.4 degrees C *65*.
Environment Associations - 1 (DRAFT) - Environment Associations
Species grunion, California
Species Id M010049
Date 27 AUG 96
SALINITY
Only half of the grunion eggs placed in freshwater in one study hatched
*65*.
A decrease in salinity tolerance with age has been reported *65*.
MOISTURE REQUIREMENTS
Grunion eggs require moisture to prevent disiccation. Interstitial water
(g water/kg sand) in grunion nests can range from 1% to 19% *65*.
POWER PLANT EFFLUENTS
An unidentified nonthermal component of power plant effluents significantly
reduces hatching success of grunion. At all test temperatures in one
study, the percentage of eggs hatched in effluent water was lower than the
percentage hatched in sea water collected before passage through the power
plant *65*.
Exposure of eggs to benzo- (a)pyrene levels of 24 ppb or more decreased
hatching percentage and increased morphological anomalies *65*.
COMMENTS ON BREEDING ADULT ENVIRONMENTAL ASSOC_ -
Grunion spawn on the beach. The female excavates the semifluid sand to
bury herslf up to her pectoral fins. Occasionally females completely bury
themselves in the nest *65*.
California grunion are caught by hand by sport fishermen during the open
season when the fish spawn on beaches above the surf line at night *65*.
COMMENTS ON LARVAE ENVIRONMENTAL ASSOC_ -
Newly hatched larvae usually live at or near the water surface *65*.
Water temperatures of 29.8 C and above reduce the viability of grunion
larvae. An increase of about 9 degrees C is required to double the
development rate. Yolk-sac larvae have shown a preference for water
temperature near 25 degrees C, well above the range that produces maximum
growth. The ability of larvae to metabolize food (protein) decreases above
25 degrees C and below 16 degrees C (fat). Growth rates are positively
correlated with temperature between 18 degrees and 25.4 degrees C *65*.
Lower and upper lethal salinities for prolarvae have been found to be 4.2
and 41 ppt and for 20 day old post larvae these salinities were,
respectively, 9 and 30 ppt *65*.
COMMENTS ON EGG ENVIRONMENTAL ASSOC_ -
TIDES
Agitation is necessary because larval movement does not aid in escape from
the egg shell. Seawater and agitation probably stimulate the release of an
enzyme that softens the covering of the egg. Eggs do not usually hatch
prematurely unless the eggs are washed free *65*.
The evolution of egg size and yolk volume in grunion has apparently been
influenced by the tides more than by temperature or any other factor *65*.
In possible response to the more irregular tides of California, the eggs
from the California grunion are much larger than those of their closest
congener, Leuresthes sardina from the Gulf of California. Cyclic tides also
deposit additional sand over the developing eggs. This provides protection
from thermal, osmotic, and desiccation stresses as well as predation *65*.
TEMPERATURE
Grunion eggs hatch over a water temperature range of 14.0 to 28.5 degrees
C *65*.
SALINITY
Environment Associations - 2 (DRAFT) - Environment Associations
Species grunion, California
Species Id M010049
Date 27 AUG 96
Only half of the grunion eggs placed in freshwater in one study hatched
*65*.
LIGHT
Exposure to light seems to reduce hatching success of grunion eggs *65*.
MOISTURE REQUIREMENTS
Grunion eggs require moisture to prevent disiccation. Interstitial water
(g water/kg sand) in grunion nests can range from 1% to 19% *65*.
POWER PLANT EFFLUENTS
An unidentified nonthermal component of power plant effluents significantly
reduces hatching success of grunion. At all test temperatures in one
study, the percentage of eggs hatched in effluent water was lower than the
percentage hatched in sea water collected before passage through the power
plant *65*.
Environment Associations - 3 (DRAFT) - Life History
Species grunion, California
Species Id M010049
Date 27 AUG 96
LIFE HISTORY
MORPHOLOGY/IDENTIFICATION AIDS
Dorsal fin V-VII + I, 9-10; anal fin I, 21-24; midlateral scales, 75;
gill rakers 5-7 + 28-29; vertebrae 47-50. Body elongate and slender; eye
diameter equal to snout length; maxillary not reaching pupil; premaxillary
protrusible; jaw teeth lacking or minute; anal fin begins below 1st dorsal
fin; scales between dorsal fins 7-9.
Color in life: greenish above, with a silver-blue lateral stripe; silvery
below; bluish blotch on cheek *65*.
SPAWNING
The grunion's unique spawning habits have long been recognized and it has
been called the "fish that spawns on land". Through this unusual
behavior, the California grunion has traded numerous marine perils for fewer
terrestrial hazards, and thereby improved the probability of egg survivial.
The spawning season begins in late February or early March and may extend
to early September; peak spawning is in April and May. The protracted
season may vary from year to year by several months. Most females in their
third year of life (age-group II) begin spawning early in the season
(April-May), whereas fish in their second year of life (age-group I) spawn
somewhat later (May-June). About 30% of the females will have spawned in
March, 75% by late April, and 90% by early May. The remaining 10% spawn
from May to September. In late July, only 7% of the females examined
contained mature ova, and in late August only immature ova were observed
*65*.
Grunion spawn as far north as New Brighton State Beach, Monterey Bay and as
far south as Mexico. The largest grunion spawning runs typically are along
the beaches in southern California *65*.
In grunion spawning waters there are two high and two low tides daily. The
higher of the high tides is at night in spring and summer. Each month,
these higher tides reach their peak at the full and new moon. California
grunion spawn every 4 weeks during the full moon tidal series. Apparently
an individual grunion may spawn about every 2 weeks during both the full and
new moon cycles. Female grunion are known to spawn as many as eight times
a season on consecutive runs. Grunion begin spawning two to six nights
after the peak tides of each cycle, when each succeeding tide is lower than
that of the previous night. Only three or four nights are suitable for
spawning during each cycle. The spawning runs begin immediately after high
tide.
At first, several fish, normally males, are swept up the beach and become
temporarily stranded on the sand as they swim against the receding water.
Gradually increasing numbers of both sexes beach themselves with succeeding
waves. Spawning begins about 20 minutes after the first fish appear, peaks
in one hour, and lasts 30 to 60 minutes. During peak spawning, thousands of
grunion litter the beach. When the tide has ebbed about one foot, the
night's run terminates as suddenly as it began *65*.
Typically, females are accompanied by one or more males as they swim toward
shore. Using a beach seine, twice as many males as females were captured
during a spawning run in one study. If males are not present when the
female is ready to spawn, she returns to the sea without laying eggs.
During spawning, the female arches her body, keeping the head up while the
caudal fin vigorously excavates the semifluid sand. As the tail sinks, the
Life History - 1 (DRAFT) - Life History
Species grunion, California
Species Id M010049
Date 27 AUG 96
female twists her body and digs tail first until she is buried up to her
pectoral fins. Occasionally females completely bury themselves in the nest.
After the female is in the nest, up to eight males attempt to mate with
her. The males curve around the female, placing their vents close to or in
contact with her body. Concurrently, the female emits eggs 50 to 75 mm
below the surface of the sand. The males discharge their milt into the sand
near the female and immediately retreat toward the ocean. The milt flows
down the female's body until it reaches the eggs below. The female then
twists free and returns to the sea with the next wave. Generally about 30
seconds elapse from "nest" digging to egg laying but some fish remain on
the beach for several minutes *65*.
Waves tend to erode sand from the beach as the tide rises and to deposit
sand as it falls; consequently, falling tides deposit more sand (41-46 cm)
over previously buried eggs, which helps protect the eggs during low tides.
The eggs remain in the sand for about 10 days, until the higher tide of the
next lunar series erodes the sand and washes the eggs free. Eggs do not
hatch until they are uncovered and agitated by the surf. Eggs of a single
clutch hatch within 2 to 5 minutes. Agitation is necessary because larval
movement does not aid in escape from the egg shell. Seawater and agitation
probably stimulate the release of an enzyme that softens the covering of the
egg. Eggs do not usually hatch prematurely unless the eggs are washed free.
For example, eggs laid on a calm night were washed free the next night by
high waves during a storm; the result was complete mortality *65*.
FECUNDITY
Fecundity is positively correlated with the size of the female. In various
studies, eggs per nest have ranged from 1,149 to 3,600 *65*.
OVA DEVELOPMENT
Immediately after the fish spawn, a second maturing class of eggs begins
differentiating and is spawned 15 days later. This 15-day cycle continues
throughout the period of spawning; therefore, as the season progresses, a
slight time lag is established between the 2-week tidal peaks and the
spawning dates *65*.
The California grunion egg is spherical and about 1.6 mm in diameter at
hatching. The eggs lack the filaments attached to eggs of many atherinid
species. Newly deposited eggs have many oil globules. The size and number
vary during development until only one large uncolored oil globule remains
in the yolk sac of the larva. The rate and duration of egg development is
in synchrony with the tidal cycle *65*.
LARVAE
In contrast to larvae of other marine fishes, California grunion are large
and well-developed when hatched. They are 6.5 to 6.8 mm long at hatching
and 7.8 to 8.0 mm long after three days. Newly-hatched grunion are
extremely active and the eyes and jaws are functional. The larvae are
capable of immediate feeding but retain a yolk sac for 4 to 6 days.
Laboratory feeding studies have shown that grunion larvae can live for a
long time without food -- some as long as 3 weeks *65*.
Newly hatched larvae usually live at or near the water surface. Larvae do
not begin active feeding until the second day after hatching. Between the
fifth and ninth day, swimming activity increases and they descent slightly
below the surface film *65*.
Life History - 2 (DRAFT) - Life History
Species grunion, California
Species Id M010049
Date 27 AUG 96
The young fish grow rapidly and are about 127 mm long at the end of their
first year of life *65*.
ADULTS
Except for spawning habits and behavior, little is known about the adult
stage in the coastal zone. Grunion populations seemingly move little along
the shoreline, but seasonal inshore-offshore movements not associated with
spawning are well-documented *65*.
MATURITY AND LIFE SPAN
Grunion mature in their second year of life and have a short life span.
They apparently spawn in their second year of life (age group I). The
largest grunion collected by one study was a 3-year-old male 170 mm long
*(65)*.
GROWTH CHARACTERISTICS
Growth of grunion is most rapid during the first year of life and then
declines in following years. At the end of the first year the mean total
length is about 110 mm for males and 119 mm for females. After the second
year's growth, average lengths are 129 and 140 mm. For the few fish
reaching the beginning of a second spawning season, the average lengths have
been found to be 143 mm (males) and 154 mm (females). The largest fish
which has been reported was 191 mm long *65*.
PREDATION
All life stages of grunion are preyed upon by a number of predators. Eggs
buried in the beach sand are fed upon by sand worms, shore birds, and even
ground squirrels. Shorebirds such as marbled godwit and whimbrel actively
probe the sand in search of grunion eggs. An isopod, two species of flies,
and a beetle have also been reported to prey on buried grunion eggs.
Juvenile and adult grunion are preyed upon by halibut, sand bass, white
croakers, and other large predators, including man *65*.
LIFE HISTORY CODES -
Breeding/Spawning Season: February
Breeding/Spawning Season: March
Breeding Spawning Season: April
Breeding/Spawning Season: May
Breeding/Spawning Season: June
Breeding/Spawning Season: July
Breeding/Spawning Season: August
Breeding/Spawning Season: September
Mating System (Single breeding season): Polygamy (mal
Mating System (Single breeding season): Promiscuity (
Duration of Pair Bond: No pair bond formed
Spawning Site: Sand
Nest Materials: Sand
Gestation/Incubation Period: 1-2 weeks
Average Number of Offspring/Reproductive Effort: 1,00
Number of Broods/Litters (Reproductive Efforts) Per Ye
Periodicity: Active in day
Life History - 3 (DRAFT) - Life History
Species grunion, California
Species Id M010049
Date 27 AUG 96
REFERENCES FOR LIFE HISTORY- 65
Life History - 4 (DRAFT) - Management Practices
Species grunion, California
Species Id M010049
Date 27 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Existing Regulating harvest of species being described
Existing Regulating harvest - restricting weapons/gear use
Existing Regulating harvest - setting seasons
Existing Other management practices [specified in comments]
Adverse Changing tidal cycle/ current patterns
Adverse Salinity alteration
Adverse Other management practices [specified in comments]
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Other management practices [specified in comments]
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 65
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 65
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 65
COMMENTS ON MANAGEMENT PRACTICES -
COMMERCIAL AND SPORT FISHERY
California grunion are caught by hand by sport fishermen during the open
season when the fish spawn on beaches above the surf line at night. The
commercial catch of grunion is taken incidentally while fishing for other
species and is marketed fresh as "smelt". Limited quantities are used for
live bait *65*.
A few grunion are landed commercially by round haul nets and lamparas and
are sold for bait or marketed as smelt in the fresh-fish market. Most
grunion landed commercially are taken in late winter and in spring just
before the spawning season *65*.
Grunion are occasionally taken in pure hauls of up to 4 or 5 tons. Only
then are grunion sold as fresh fish and then only if smelt are relatively
scarce. Otherwise, the mixed catch is sold as bait or to canners of pet
food *65*.
REGULATION
In the 1920's, the grunion fishery began showing signs of depletion , which
was probably due to overfishing and habitat alteration. From 1927 to 1946,
the fishing season in California was closed from April to June. Grunion may
now be taken by sportsmen only by hand throughout the year except in April
and May. Although the population size is unknown, the resource appears
to be maintaining itself under the present sport fishing intensity. Since
grunion populations seldom move laterally along the shoreline, local
controls maybe adequate for management *65*.
POWER PLANT EFFLUENTS
An unidentified non-thermal component of power plant effluents significantly
reduces hatching success of grunion. At all test temperatures in one
study, the percentage of eggs hatched in effluent water was lower than the
percentage hatched in sea water collected before passage through the power
plant *65*.
Management Practices - 1 (DRAFT) - Management Practices
Species grunion, California
Species Id M010049
Date 27 AUG 96
OTHER POLLUTANTS
Exposure of eggs to benzo(a)pyrene levels of 24 ppb or more decreases
hatching percentage and increases morphological anomalies *65*.
SALINITY
Only half of the grunion eggs placed in freshwater in one study hatched
*65*.
TIDES
Agitation is necessary because larval movement does not aid in escape from
the egg shell *65*.
A decrease in salinity tolerance with age has been reported *65*.
Management Practices - 2 (DRAFT) - References
Species grunion, California
Species Id M010049
Date 27 AUG 96
References
65* Fritzsche, R.A., R.H. Chamberlain, R.A. Fisher. 1985. Species
Profiles: Life Histories and Environmental Requirements of
Coastal Fishes and Invertebrates (Pacific Southwest) --
California Grunion. U.S. Fish and Wildlife Service Biol. Rep.
82(11.28) pp 12.
References - 1