Reproduction and early life history of the Sculpin

Have you ever personally thought that fish were an interesting subject? Most people don’t. The majority of individuals consider fish ordinary, routine and insignificant. However with a closer look, you may discover that fish can be extraordinary and extremely significant in more ways than one. With proper education and better understanding, people will not only realize the importance of the fish, but also the relevance of issues such as the spawning, life history and life span of fish such as Jordania zonope (sculpins).
Prior to the spawning season (December-January), the males move into the spawning zone in fresh water or brackish water and are later joined by the females (Krejsa 1967; McAllister and Lindsey 1960), [On-line]. Krejsa (1967) has reported that spawning migration is limited to the coastal population and does not occur in the inland population. Judging from the location of sculpin larvae taken in this study, both migratory and nonmigratory populations exist. Spawning takes place February through June (Krejsa 1967), [On-line]; mainly in March and April (Moyle 1976), [On-line]; February through May (Millikan 1968), [On-line]; January through September; January through May in Central Valley floor waters; and May through September in the foothill creeks.
The average temperature for spawning is 8-13 C (Krejsa 1967). The saltinity is 12 ppt (Millikan 1968); freshwater to intertidal (Moyle 1976); freshwater to oligohaline. Some substrates are large cobbles or flat rocks (Krejsa 1967); under surface of rocks, in beer cans, rusting automobile bodies (Millikan1968), [On-line]; trash (Moyle 1976), [On-line]; under-surfaces or crevices of rocky bottoms and banks, jetties; concrete blocks and other artificial substrates.
For both fresh and salt water sculpins mating activity occurs mostly at

night or during darkened conditions. Freshwater male sculpins cleans and

prepares a nest cavity for the female to lay her eggs; when the female lays her

eggs she deposits them in clusters on the underside of the nest that the male has

prepared for her. The saltwater female sculpin chases a male until she traps him

in a crevice. She keeps him there until she lays her eggs. A mature male then

fertilizes the eggs. A mature scalyhead sculpin has a well-developed, penis-like

appendage that it uses to fertilize the female internally. Sculpin eggs are often

brightly colored-green, blue, yellow, orange, pink, red – perhaps to warn off

predators. This is a form of protective coloration among many species, which

use bright colors to warn predators of danger. The number of eggs that are

found in the ovary are 336-5,652 and 700-4,000 per cluster

(Krejsa 1967); 584-10,980 eggs in ovary (Bond 1963), [On-line]; 280-7,410

eggs in ovary (Patten 1971), [On-line]; 1,094-5,656 (Millikan 1968), [On-line].

Several females may lay their eggs in one males nest. The female may

also lay eggs in more that one males nest. After the eggs are laid the male goes

into the nest and fertilizes the eggs immediately . The male fish guards the nest

three to four weeks or until the fry leave. He aerates the eggs by fanning them

with his large pectoral fins until hatching occurs (Krejsa 1967), [On-line]. The

reason the male fans the eggs is to keeps the eggs clean from bacteria and to

keep oxygen flowing to eggs. The male also removes debris and dead eggs

with his mouth from his nest. The father is so attentive, he may net even feed

until the eggs hatch. Eggs adhere strongly to one another, but less to other


Incubation is relatively long: 15-16 days at 12 C (Krejsa 1967), 19-20 days

at 10-12 C (Mason and Machidori 1976), [On-line] and 14-15 days at nine to 13 C

under laboratory conditions. Millikan (1968) noted that hatching rate of prickly

sculpin eggs is higher at a salinity of 12 ppt than in fresh water.

A Newly fertilized egg is one point four millimeters in diameter. When the

egg is in the stage of morula, it is one point four millimeters in diameter. The egg

is one point five millimeters in diameter when it is at the early stage of being an

embryo. During the late stages of being an embryo the egg is one point five

millimeters in diameter. Most of the sculpins eggs are shaped spherically.

The yolk is