Camille Eastburn
A.P. Goyke
Ichthyology
October 2, 2015
Various Survival Behaviors of Fishes
The various behaviors of fish are fascinating, yet strange. The field of fish psychology can sometimes also be overlooked although, it plays a vital role in ecology. This paper discusses four different fish behaviors such as, migration, aggression, feeding and shoaling. Many of these behaviors impact each other, therefore discussing a single one would not be sufficient.
Migratory behavior is a common survival behavior in animals, and fish are no exception. Fish can migrate based on resources and their environment, these vary from daily to seasonal. “Daily migrations typically are for feeding and/or predator avoidance” (Moyle, P.B. and J.J. Chech Jr. 2004), whereas seasonal results in major changes in the location. The general patterns of fish migration are broken up into three other categories: Oceanodromy, potamodromy, and diadromy. Oceanodromy refers to fish that only migrate is salt water, and potamodromy refers to fish that migrate in fresh water. Diadromy refers to the ability of certain fish to migrate between both salt and fresh water. Examples of diadromy include, White Sturgeon, Atlantic Sturgeon, Siberian Sturgeon, Shortnose Sturgeon, and Green Sturgeon ( McDowell R.M 1999). Many diadromy are extinct or vulnerable, because little is known about conservation methods of these fish. Diadromy are also split into three categories.
The categories that diadromy are split up are the following: Catadromy, anadromy, amphidromy. Catadromy are fish that spend most of their life is fresh water, only traveling to salt water to spawn, and once they are in the salt water they do not feed i.e. eels. Anadromy are the opposite of catadromy, growing in salt water and only venturing in to fresh water to spawn i.e. salmon and trout (McDowell R.M. 1988). Amphidromy move between both salt and fresh water their entire lives. After they hatch, the move to the salt water to feed for a short time, then they return to fresh water. In the freshwater, they grow to full size and spawn. Examples of these fish are often seen around islands. A highly migratory fish that makes very large migrations is the Albacore Tuna. This species of tuna is able to cross entire oceans. Many species of tuna are known for their large migrations.
Fish migrations are immense and spectacular. It takes enormous amounts of energy to travel the distances that they do. In fact, quite often, migrating fishes do not feed, such as the catadromy when they enter salt water. While a large reason why fish migrate is reproduction and separation of life stages (Moyle, P.B. and J.J. Chech Jr. 2004), they also have response migrations. Fishes migrate in response to their environment such as temperature and abundance of food. The response due to temperature and food changes can be seen in various types of marine fish and not as much in fresh water fish. Understanding these migrations is important for humans to predict good or bad fishing, even months in advance.
A behavior of fish that is commonly observed is aggression. Depending on the type of fish, aggressive behaviors can range from direct charges, which can result in conflicts, like biting and fighting, changing of colors, to flaring of fins/gills. Fishes show the most aggression when dealing with reproduction and the defense of breeding territories, while showing lesser aggression when dealing with the defense of food and space. The technique most often used by fishes to attack a potential intruder is the “nip”, where the fish launches from the protected area, and attempts to nip at the caudal fin or side of this fish (Moyle, P.B. and J.J. Chech Jr. 2004). “Sizing up” the intruder or the assailant is another technique fishes use. If there is an obvious size difference between the fishes then the one at a disadvantage will flee, however if they are nearly the same size, then it may result in a fight. Occasionally, a larger intruder will displace smaller fish, meaning that they will coexist in the same area, with the largest fish ruling in a complex hierarchy. These fishes can coexist because there is no competition for food between the different sized fishes.
Fish feeding behaviors are incredibly diverse. This behavior mirrors their feeding methods. Most fish are specialized or not specialized in certain type of feeding. The Great White Shark is specialized in swift, surprise attack, from the bottom, which can prove to be one fatal bite. Occasionally, the abundance of prey will not be sufficient for fish and they will have to switch their food source or migrate. The Great White will become a scavenger of whale carcasses if there are not seals in his vicinity. The reason predators pick their prey has to do with optimal foraging. Optimal foraging helps predict how an animal behaves when it's searching for food. Although obtaining food provides the fish with energy, searching for and capturing the food require both energy and time (Werner, E. E.; Hall, D. J. 1974). The fish wants to gain the most benefit for the lowest exerted energy during foraging, so that it can maximize its fitness. The optimal foraging method can be seen in many fish, which will eat prey that is nearly the same size as them. An exception to this theory is when food sources are scarce. A fish will eat any size prey, no matter how small, or if the energy gain has a negative correlation to the energy exerted.