1. Using the Slope of a Line to Estimate Fish Weight

2. Fish Grow All of Their Lives They first start out as an embryo in an egg. Then they hatch out as a larvae. Then they develop into a juvenile. Then they become an adult.

3. Fish Growth As fish grow, their weight increases proportionally to their length.

4. Determining the Length-Weight Relationship First, you need to measure the length and weight for several fish. Length

5. Graphing the Data The next step is to graph the data and draw a line of best fit.

6. The Line Equation Y = mX + b The ‘slope’ of the line (m) is the relationship between length and weight. Increase in Weight Increase in Length Slope

7. Estimating Weight From Length Once you know the length-weight relationship for a species, you can estimate the weight based only on the length! Y=mX + b

8. Estimating Weight From a Line Equation Our Line Equation is: Weight = 0.9909(Length) + 0.2814 How much would you expect a 12 cm fish to weigh? Weight = 0.9909(12) + 0.2814 Weight = 11.8909 + 0.2814 Weight = 12.1722

9. Comparing Fish Species Some fish are long and skinny and some are short and fat.

10. Comparing Fish Species The length-weight relationship for long skinny fish is different than for short fat fish. Long and Skinny Fish Short and Fat Fish