Fish Behavior

1. Fish Behavior Yes, this is a wonky angle

2. Territoriality It’s a fun word Most fish are not territorial Those that make territories guard them for food and shelter More common in crowded communities, such as in the coral reef and kelp bed ecosystems Some only guard them during breeding season The territorial fish use a variety of aggressive behaviors to keep others off their spot

3. Territoriality Continued Fish fights are rare, instead they bluff to avoid injury. Raised fins, an open mouth, and random darting about are some of these behaviors. Some fish also use sound production as a way to keep fish off their turf. Fish either use scraping of one bony part against another, or utilize muscles on the swim bladder to make a “drumming” noise Occasionally a fish will protect it’s territory by itself, while other species use male-female pairs, or groups that then divide the territory into subterritories.

4. Schooling Schools are large groups of fish that are generally highly coordinated, as every fish keeps a constant distance between itself and its neighbors, while vision plays an important role in the spacing, the lateral line system and olfaction play a large role because even blind fish can form schools! Fish in this group include: herrings, mullets, sardines, some mackerels, mantas, and hammerhead sharks Approximately 4,000 species of fish school as adults including aquatic and marine fish The leader of a school is in the center of the group One explanation for schooling is the increased protection from predators in numbers, using numbers to their advantage fish can confuse a hunter by either streaming past the predator or encircling it

6. Migrations • Migrations are regular mass movements from one place to another over any time period, for squid from the deep during the day to near the surface to feed at night, for students from the house to school then back again • Parrotfishes and others migrate onshore and offshore to feed • Most migrations in fish are related to feeding or reproduction

7. Anadromous • Anadromous fish live at sea most of their lives then migrate upriver to breed, sturgeons whose eggs are used as caviar are anadromous, but the most widely known anadromous fish by far is the salmon • (Pacific Salmon migrating)

8. Pacific salmon • There are seven species of salmon in the Pacific, each is known by different names. The salmon spend the majority of their lives in the North Pacific traveling the coastlines, some even go to the Bering sea and the Arctic Ocean. We don’t know how they navigate their way around but some have hypothesized that the fish use physical land marks, currents and salinity to help find their way. After several years the salmon mature sexually and move back to the stream that them hatched in, they get there using some type of chemical memory. This is the salmon’s homing behavior.

9. The eggs are put in shallow holes called “redds,” fertilized then buried, the adults protect the nest until they die. Some species of salmon return to the ocean right away, others such as the sockeye stay up to five years in the stream or river. • Environmental changes made by humans, such as dams, have restricted the return rate of the salmon to their spawning grounds cutting growth, also fertilizer runoff can mess with the sense of “smell that the fish have, making it less likely that the salmon will get back home.

11. catadromous • Catadromous fish have a migratory pattern opposite that of the salmon’s, Atlantic eels have the longest journey of these fishes

12. Reproductive systems • The sexes are usually separate. Both sexes have paired gonads internally. In cartilaginous fishes the ovaries and the testes are connected into the cloaca. Bony fishes have a separate opening for their gametes, called the urogenital opening, located behind the anus. Many fish’s gonads only produce gametes during a particular time in their life. The timing is important because in order to breed, the males and females need to mature sexually at the same time. The timing is critical for fishes that endure long migrations.

13. Hormones are responsible for the timing of the sexual reproduction. The sex hormones are released in small amount into the blood stream to stimulate the gametes maturation, these hormones may change the fish’s: shape, color or behavior. The release of the hormones is triggered by environmental factors such as the length of day, temp, and the availability of food.

14. Sex changing • Hermaphrodites are fish that are both male and female, the fish can produce both eggs and sperm. Simultaneous hermaphrodites mostly live in the deep ocean where finding a mate can be difficult. A variation of this is sequential hermaphrodites, where the fish start of as males then change into females (protandry) or female to male (protogyny) the changes are controlled by hormones but triggered by social ques.

16. Reproductive behaviors • Fish need to get together to make babies. many bony fishes change color to indicate that they are ready to breed. Courtship is the first step, this is a series of active movements, “dancing,” posture to display colors and swimming upside down are all way to get fish mates. All species of fish have different ways to attract the opposite sex, this prevents confusion between species. While some fish have internal fertilization (cartilaginous fish), most fish reproduce thru broadcast spawning. • Internal fertilization in sharks, ray, and skates, involves a romantic bite on the female’s back, then the male inserts one of his claspers, male reproductive organs, into the female’s cloaca.

17. Open water bony fishes and those living around reefs, spawn directly into the water after courtship. The Atlantic Cod release about 5 million eggs, but the Atlantic tarpon release over 100 million eggs at a time. Some fishes, like butterfly fishes, form long lasting relationships after breeding

18. Before hatching • After broadcast spawning the eggs are released into the current mingling among the plankton, most of these eggs die. After the few that live hatch, they must feed • Some fishes instead of broadcasting eggs hide them in nests and guard them until the eggs hatch.

19. Types of hatching • Oviparous, egg layers, external fertilization and birth. • Ovoviviparous, internal fertilization and live birth, but still inside egg case. Mostly cartilaginous fishes • Viviparous, live birth taking nutrients from the mother’s reproductive tract.