Gulf killifish facts for kids
Quick facts for kids Gulf killifish |
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The Gulf killifish (Fundulus grandis) is a type of fish found in the Gulf of Mexico. It is one of the biggest fish in its group, growing up to 18 centimeters (about 7 inches) long. Most other fish in the Fundulus group only reach about 10 centimeters (4 inches). Because of its size, the Gulf killifish is an important food source for larger sport fish like flounder and red drum.
The name Fundulus comes from a Latin word meaning "bottom," and grandis means "large." This fish lives in the Gulf of Mexico, from Texas to Florida, and also along the eastern coast of Florida and in the Caribbean Sea.
Things that can harm the Gulf killifish include big changes in how salty the water is, changes in temperature, and pollution. Events like the hypoxic dead zone in Louisiana and the Deepwater Horizon oil spill are major threats. Scientists use the Gulf killifish to study how oil and oil dispersants affect ocean animals. This research helps us understand how to protect marine life, especially with continued oil drilling in North American waters.
Contents
What Does the Gulf Killifish Look Like?
Fish Colors and Patterns
The Gulf killifish has special colors that make it stand out. Its main color is a dull greenish on top, fading to a lemon-yellow underneath.
Male and female fish have different colors. Males are much brighter, with shiny silver spots and clear stripes. Females look more olive, or dull olive if they are very large.
You can also see stripes, spots, and different colors on their bodies. Some fish have stripes near their head, but these often fade as the fish gets older. Small, shiny spots are found along their sides. The fins near their tail and belly might be yellow, or they might be darker with white patches at the base.
When male fish are ready to breed, their colors change even more. They become deep blue on their backs, with blue fins that have light blue spots and yellow-orange edges. Generally, the Gulf killifish has a yellowish or pale belly and a darker back with many pale spots and patterns.
Body Features
The Gulf killifish has many scales. It has more than 15 rows of scales between its belly fin and its throat, and 31 to 39 rows along its body. Around its tail, there are about 17 to 20 scales. It also has 12 to 19 faint stripes along its sides.
This fish has five pairs of sensory pores under its lower jaw, which help it sense its surroundings. It also has about 9 to 12 gill rakers, 10 to 12 rays in its dorsal fin, 9 to 11 rays in its anal fin, and six rays in its pelvic fins.
While the Gulf killifish can grow up to 18 centimeters (7 inches), it is usually around 10.4 centimeters (4 inches) long. They have a blunt head and a short snout. Their mouth is almost at the very front, with the lower jaw sticking out a little.
The dorsal fin is usually located a bit in front of the anal fin. The anal fin is rounded, and its base is more than half the length of its longest rays. The gill slit is important because it controls how much water flows through the gills. For Gulf killifish, their gill slit extends above their top pectoral-fin ray. Overall, the Gulf killifish is one of the largest killifish species with a blunt head and short snout.
Where Do Gulf Killifish Live?
Types of Homes
The Gulf killifish can live in many different places because it can adapt very well. Over time, they have changed to survive in various habitats, which helps them live longer. These places include estuaries (where rivers meet the sea), coastal marshes, lagoons, rivers, and streams. However, the Gulf killifish spends most of its time in brackish water near the coasts.
Where They Are Found
You can find the Gulf killifish in the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea. They are also found along the Southeast United States Continental Shelf. Their normal range is from Texas to the western coast of Florida, and from the east coast of Florida throughout the Caribbean. The water in these areas can change a lot in terms of temperature, oxygen levels, and saltiness. These changes can greatly affect how well the Gulf killifish survive and how many there are.
How Salty Can the Water Be?
Since Gulf killifish live near the coasts, they can handle many different levels of saltiness, even fresh water. This is because their habitats often get fresh water flowing into them. They can survive in water with salt levels from 0 to 76 parts per thousand (ppt).
However, big changes in saltiness can be dangerous for them. The salt level greatly affects how their eggs develop and hatch. For example, after the Deepwater Horizon oil spill, canals were opened to send fresh water into the Gulf. This was done to push oil away from the Louisiana marshes. But it caused the water to become less salty very quickly in some areas where the fish lived. Many eggs did not hatch because the salt levels dropped too low.
Studies have shown that fish raised in less salty water were less likely to survive. They also grew to be much smaller. Young killifish (2 weeks old) grow and survive less well in fresh water. But by 7 weeks old, they can live in fresh water without slowing their growth. This is because young Gulf killifish can control their body's salt balance early on. These studies show how important saltiness is for the survival of the Gulf killifish.
Water Temperatures
The Gulf killifish usually lives in warm, tropical climates. However, they can survive in temperatures ranging from 5 to 37 degrees Celsius (41 to 99 degrees Fahrenheit). Temperature is very important for their eggs to hatch and be healthy.
Lower water temperatures, especially with shade in summer months (June, July, August), lead to the most healthy eggs. But in September, when the water starts to cool down, extra shade can make the water too cold. This leads to far fewer and less healthy eggs. This shows that temperature greatly affects the overall survival of the Gulf killifish.
Oxygen in the Water
Another key factor for Gulf killifish survival is the amount of oxygen dissolved in the water. Fish need oxygen to live and do their normal activities. Low oxygen levels are common in coastal areas, which are main habitats for the Gulf killifish. These low oxygen conditions can last for hours or even days.
Gulf killifish have ways to deal with low oxygen. They can change their behavior, how their bodies work, and their internal processes. A major threat that lowers oxygen levels is the Louisiana dead zone. This area kills many fish every year. It happens when water rich in nutrients and chemicals from the Mississippi River flows into the Gulf of Mexico. This causes too much algae to grow, and when the algae die, decomposers use up all the oxygen in the water. Fish that cannot leave the dead zone in time will die from lack of oxygen. Fish caught in the summer are better at handling low oxygen because they are already used to it due to higher summer temperatures.
How Pollution Affects Gulf Killifish
Young Gulf Killifish (Larvae)
The Gulf killifish lays its eggs in the soft, muddy bottoms of salty or brackish water. They are sometimes called "annual" fish because their life cycle, from hatching to mating and dying, usually lasts less than one year.
A special feature of the Gulf killifish is how tough their eggs are. The egg shell not only protects the baby fish inside but also stops them from drying out. The shell can sense how much oxygen and carbon dioxide is in the water, which helps decide when the eggs should hatch. However, human activities can harm this natural process if they pollute the water where the eggs are laid.
Oil or oil dispersants in the water can be very dangerous for young Gulf killifish. The danger depends on how long the eggs are exposed and the weather conditions. Oil and dispersants can sink into the mud where the eggs are laid. These substances can then harm the developing baby fish or newly hatched larvae. This can lead to problems like undeveloped hearts, weaker nerve functions, fewer hormones, and poor gill development.
Adult Gulf Killifish
Gulf killifish become adults when they are about three to four months old, but on average around one year old. They can grow to be about 6 to 7 inches long when fully grown. Female fish can grow 5 to 8 centimeters (2 to 3 inches) larger than males. Females might also act more aggressively during mating season.
Once they are adults, Gulf killifish eat both plants and animals. They feed on algae, water plants, small shrimp, tiny crustaceans, and mosquito larvae. Eating mosquito larvae helps control the mosquito population in marsh and wetland areas. Gulf killifish are also a popular bait fish for people who fish for fun or for business.
How Gulf Killifish Adapt to Pollution
Scientists have found that Gulf killifish living in the very polluted Houston Ship Channel have become resistant to the effects of pollution. This means their babies are protected from heart problems caused by pollution, unlike fish from cleaner areas.
These adapted Gulf killifish also seem to be more resistant to pesticides and stress, and they have a faster metabolism. This might be because they have had to adapt strongly to survive in very polluted water. This ability to resist pollution suggests that animals can adapt to human-made contaminants in their environment. This kind of adaptation is seen in many fish species.
The Deepwater Horizon Oil Spill and the Killifish
The Gulf killifish played an important role in scientific studies after the Deepwater Horizon oil spill. This huge oil spill happened in April 2010. About 53,000 barrels of crude oil spilled into the Gulf of Mexico every day until September 2010. The spill affected the Gulf coast for about a year, and it was finally declared contained in October 2011. Many projects are still working to restore the Gulf's ecosystems.
Macondo-252 Crude Oil
How Gulf killifish react to the Macondo-252 crude oil depends on their age and how long they are exposed. When this oil spills into water, it floats on the surface and affects fish. The oil can harm fish in different ways. Floating oil can touch the Gulf killifish if they swim through it or if the oil drifts into them. During the Deepwater Horizon spill, over 205 million gallons of crude oil formed a huge slick.
The floating oil harmed the fish by being absorbed through their gills and getting into their eyes. This caused many health problems for them. The Macondo-252 oil can also sink deeper into the water and settle in the mud at the bottom. This creates a new danger, especially for the developing eggs and young larvae of the Gulf killifish. Oil in the mud can get into the developing fish, causing direct harm.
Corexit 9500 (Oil Dispersant)
Scientists have also studied how the oil dispersant called Corexit 9500 affects Gulf killifish. Corexit 9500 is a hazy, amber-colored liquid that helps break down oil. It is sprayed by airplanes onto floating oil slicks to make the oil sink to the bottom of the water.
Corexit 9500 was the main oil dispersant used during the Deepwater Horizon oil spill. It affected many coastal water ecosystems in the Gulf. Studies have shown that this dispersant can harm the internal body processes of some marine species, including the Gulf killifish.
See also
In Spanish: Fundulus grandis para niños
