FISH ECOLOGY Unit 2. Fish Ecology Lesson 1. --What is a Fish? Lesson objectives: Students will understand external fish anatomy, and that fish come in many shapes and sizes The students will be able to identify the different zones of the ocean Students will become familiar with the methods that are used to study fish are diverse, and each has a purpose. Vocabulary words: vertebrae, planktonic, nektonic, benthic, continental margin, and many more pertaining to ocean zonation What is a Fish? A fish is defined as an aquatic lamprey and hagfish; and the or marine animal with shark, ray, chimaera, lungfish, vertebrae. All fish have and bony fishes. The bony vertebra, except sharks and fishes are the most common. A rays that have cartilage. bony fish has jaws that are well Cartilage is more flexible than developed, formed by true bone bone, but strong enough to rather than cartilage. Fish are support the body. They usually very different in appearance, possess gills in the adult stage size and shape. This all and have limbs in the form of depends on the environment fins. Fishes also include the that it lives in. jawless vertebrates such as the ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 17 FISH ECOLOGY Fish Habitats Fish occupy almost every not associated with land) realm conceivable aquatic habitat. of the ocean. Describing the ocean is difficult, as there are many words that Geographic zonation defines are used to explain the land the coastline, and submerged and water realms. These land. Scientists use these habitats are defined by the words to help in the critters that live in each. identification of animals that live Visualize a column of water. on the substrate (land). This is the pelagic (the water, Some fish live in man made habitats in peoples homes. These habitats are called aquaria. between the continents and ocean basins. The continental margin includes the coast (also There are other terms that known as the littoral zone), the describe the geographic zones continental shelf, the that pertain to the continent and continental slope, and the landmasses under the water. continental rise. The Between the continental land continental rise ends where the and seafloor is the continental abyssal plain begins. The margin. It is the submerged deepest parts of the ocean are part of the continent, and located in the trenches, or makes up a transition zone hadal areas. (Activity 1 is an illustration that is to be labeled with the different vocabulary words found in this section.) ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 18 FISH ECOLOGY Example Prefix (most English of what have Greek Realm Depth (water or land) lives origins) definition there no specific depth, just all organisms pertaining pelag(os) of the sea water found in the to the water water column realm, NOT the land plankton, fish epi outer, exterior water 0-200m larvae, very small fish active swimmers such as the meso middle water 200-600m tuna, squid and marine mammals of or pertaining crabs, littoral (littoralis) to the edge of a water and land seashore juvenile fish, origin is Latin lake, sea or boundary area plankton, ocean larvae deep sea 4000m and batho- or bathy- depth both organisms, deepter gulper eel deep area or 4000m to deep-water abyssos both space, chasm 6500m organisms flounder, stargazers, 0 (beach crabs, zone) to depth of the sea, starfish, benthos land deepest bottom urchins, ocean snails, bottoms christmas tree worms deep sea deepest part of 6500m and organisms, hadal land the sea, trenches deeper some eels, lantern fish ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 19 FISH ECOLOGY How Do We Study Fish? Scientists study fish in many containers without inflicting ways because sometimes they harm. want to observe them in their natural environment, and other Nets may be small enough that times, scientists need to one or a few persons can use observe the internal body them. These might be trailed in structures. The study of fish the water over a distance, or might be completed through the the fish may be directly caught use of SCUBA, nets, trawls, in them. Other nets are very seines, and videography. large, and require use of a boat Scientists and heavy machinery to use use SCUBA them. observe fish in their Beach seines are long mesh natural nets with lead weighing down habitat, the bottom of the net, and collect them styrofoam or airfilled floats on to dissect or the top of the net that stay at observe live, the water’s surface. Wooden or capture poles attached to either end of their movements on video the net are used to move the camera. Another way that a net through the water. Seine scientist studies fish is with the nets may be used nearshore use of a manned or unmanned where the leadline will rest on ROV (Remotely Operated the bottom, while other times it Vehicle). Using an ROV, a may be used in the pelagic scientist may observe fish and realm, and never rest on the their habitat without disturbing bottom. Sometimes, a seine it. ROV's are extremely useful net will have a bag or a sack for scientists to use at great attached to the middle of the depths. When an ROV is used net to help in the capture of fish for research, the materials are in the center of the net. almost always captured on video. They are also useful for Otter trawls are much like seine capturing live fish into nets. They are dragged across the bottom of seagrass and soft ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 20 FISH ECOLOGY sediment communities for the (mouth) as it is towed. There sampling of demersal and are instruments at the top to near-bottom fishes as well as collect information about the epifaunal invertebrates. The water (such as temperature, structure of the otter trawls is salinity, depth, and chlorophyll). slightly different in that they are In this schematic, there are shaped like an ice cream cone. eight nets. A computer can control each net to open and otter boards close at various depths. Samples are collected at each float line lead line Cod end Otter Board The fish are captured in the cod-end of the net. This is the pointed end of the cone. Often within the mouth of the net, scientists will attach a plankton net. The plankton net captures Diagram 2. MOCNESS the microscopic plants and animals. That way, the fish in depth and stored until the entire the trawl do not eat them in the net is brought to the surface. In trawl, and there is something to the drawing, they all are closed, feed the live fish scientists are except one. The top net, is studying. sampling the shallowest depths on its way back to the surface. This is a sketch of a research When the MOCNESS is vessel towing a 1-m retrieved on board, the MOCNESS (Multiple Opening collectors (nets and cod ends) Closing, Net E S System). are each handled separately for The MOCNESS is a ‘special’ sorting and preserving. sampling device used to collect multiple samples at variable There are many more kinds of depths. One meter (1-m) refers nets, and special uses for each. to the open area (one square This is just a brief overview of a meter) of the net opening few that can be used. ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 21 FISH ECOLOGY Why do We Study Fish in the Ocean? Fish play an the most important sources of important animal protein for humans, thus role in many fishes are used as food. aquatic Other products made from fish ecosystems include nitrogenous fertilizers and have from fish and fish scraps and long the oil extracted from fish livers provided is one of the sources of vitamin valuable D. Fish scales are sometimes resources to used in making artificial pearls. humankind. Isinglass, a form of gelatin, is prepared from the air bladders Fish are very important of certain species, and glue is economically. Fish are one of made from fish offal. Fish Conservation Many fishes are threatened pollution and habitat with extinction including the destruction. Exotic fish have great white shark, most killifish, been introduced and often and every species of sturgeon replace or threaten native fish and paddlefish. The threat populations. Dams that keep comes from a variety of adults from reaching their sources. Seventy percent of spawning grounds hinder fish species commercially populations from reproducing. caught around the world are overexploited. That is, they are harvested beyond their ability to sustain a given population size, caught to the limit, or are recovering from overexploitation. One third of the world catch is bycatch, fish caught unintentionally and discarded as waste. Coastal fisheries are vulnerable to ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 22 FISH ECOLOGY Activity 1-1. Ocean Zonation Objective: Have the students fill in the blanks with the different vocabulary words found in the ‘Where do I Live’ section of this informational packet. Students will then learn how the ocean has many zones and places for fish to live. ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 23 FISH ECOLOGY Activity 1-1. Ocean Zonation -- Teacher's Key ©PROJECT OCEANOGRAPHY FALL 1999 FISH ECOLOGY 24 FISH ECOLOGY Activity 1-2. Fish Body Outlines Method: Outline the general body shape of your fish and identify the different body components. Save picture for use in Unit 3. Discussion: Have the students discuss the differences in body shapes, and how that might affect how a fish swims. Using this information, and looking at the coloration or pattern of their fish, the students might be able to guess, or draw conclusions about the habitat their fish might be best adapted to live in.