Fish Adaptation- Swimming and Buoyancy

Body Shape and Drag

-Inertial drag-due to pressure differences caused by fish pushing water out of its way. Displacing water. Mass, Speed, and body shape are important variables. Depth or width that is 1/4 it's length is the most hydrodynamic shape. It's the best for swimming. is called Fusiform. -Viscous drag- friction between fishes body and the water. Surface smoothness, surface area, and type of movement are important variables. Mucus also effects this- the more mucus helps to reduce viscous drag. Larger surface area=more friction. Fish who swim in schools can use the fish moving beside to reduce your own drag.

Categories of Swimming

-Rajiform- pectoral fins/ Anal fins/ Dorsal fins -Anguilliform-trunk -Subcarangiform-trunk half way down -Balistiformanal/dorsal fins -Carangiform -Labriform -Ostraciform -Modified Carangiform

Types of Thrust

1.backwards passage of transverse waves alone the body and undulating 2. Lateral movements of the Caudal fin (tail) -eel uses anquilliform -trout and seabags uses Carangiform and subacarangiform -Boxfish uses ostraciiforn and smooth trunkfish *video links on slide show "Lecture 3 Adaptation of Fishes"

Buoyancy

If not buoyant at all they would sink, if too buoyant they would just float. -Dynamic lift- using your fins or swimming motion. The problem is you have to be in constant motion, you can't hover, or swim backwards. That uses a lot of extra energy that creates more drag. Good way to generate lift if your a fish that usually sits on the bottom and only has to move a little bit or if you're a fish that has to keep swimming anyway for other reason. -Static lift is using lighter materials in your body that make you more buoyant. Examples: Fats, oils, reduced mass, and swim bladders. The idea is that they are making you the same density of the water so you don't float or sink. Fats and Lipids have an advantage because the lift doesn't vary when you go from shallow to deep water. but it is bulk to have that in your body. It can also cause some complexity in metabolism. Examples are deep sea sharks, etc. They have really large livers where the lipids are stored. (Average is 4-6% of total weight, these animals have livers 25% of total mass). Swim bladder- most teleosts. Gas swim bladders. Advantage is that the density of gas is really low so it doesn't need to be large to provide the buoyancy that is needed. Problem is that if you go up or down in the water, the buoyancy changes so you have to be able to adjust the amount of gas in your swim bladder because the pressure changes. Two types of swim bladders 1. physostomous- the more primitive. They are connected to gut through a tube. These fish gulp air and put it into the swim bladder and burps air out to get rid of it. You have to be able to get to the surface pretty quickly but can also regulate quickly. 2. pysoclistous is more derived and complicated. Pulls gas from capillaries into the swim bladder. Gas moves in and out through the blood stream. This is the type of swim bladder found in most teleosts. Most common type. You don't need to be near the surface and just get o2 from the water. but it's a lot harder to quickly change the amount of gas in the swim bladder.

Pelagic Swimmers

Swimmers that swim in water that is deep (they don't necessarily have to be deep water swimmers) need open water. -These also use their tail more than their body to swim because it decreases the drag. ex: tuna and macreal

Stability

Yawing- the movement side to side asumming that your keeping everything else the same (swerving on a road) Pitching- moving about the horizontal transverse axis (nose-diving on a plane) Rolling- being belly up All fins are important for stability (less so for tail)