Science Behind Sustainable Seafood Population Estimation Alaska Fisheries Science Center

Why is it important to estimate population size of fish? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 2

Fish are an important food source! U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 3 Sole sliders and Pollock taco recipes found at

Fishing provides jobs… U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 4

What other populations are estimated? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 5

The U.S. Census estimates population size… U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 6

Can you count all the fish in the Ocean? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 7

What challenges do you think the scientist will face in trying to count Pollock? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 8 The ocean is huge – covers about 70% of the Earth Much of the ocean is dark The parts of the ocean that Pollock live in are very cold. There are about 5 billion Pollock in the Bering Sea. Pollock are always moving around! Just knowing these facts, it is clear that a scientist isn’t going to be able to count every fish.

Physics of water… Under 33 feet of water, you have twice as much pressure on you than at the surface, at 66 feet, there's 3 times the pressure. Considering that the average depth of the ocean is feet, there's a lot of water we can't easily reach. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 9

Habitat types – another consideration Land Ocean interface sandy beaches rocky shores Continental shelf coral reefs kelp forests Fine silts and mud Coarse sands Boulders Continental slope canyons rocky outcroppings, sea mounts or pinnacles Continental rise abyssal planes deep trenches U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 10

Most of these habitats are in Alaska waters… U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 11 Aleutian Trench Zhemchug Canyon Seamounts Abyssal Plane Shelf Slope

What happens if we sample a large area with multiple habitat types and then extrapolate our sample to the entire area? We may be overestimating the population size. The density of a population may not be uniform throughout the area - density is # of x divided by the area sampled U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 12

Populations can be estimated without counting every fish U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 13

How do scientists figure out how many pollock are in the ocean? Fisheries scientists estimate population size from samples. Imaginary grid over the entire continental shelf and only sample a few of the grids. How do scientists select which grids to sample? Random sampling method ensures that areas with fish and without fish are represented. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 14

Why is it important to know population size? It is important to know if it is: Growing Shrinking Stable This information will give our government an opportunity to plan for the future. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 15

How to estimate population size… Estimation techniques line transect aerial surveys tagging animals simple observations over time. Knowledge about the population dynamics is also critical, do they migrate or are they stationary, do juveniles and adults co-occur or do they have different habitats? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 16

In the Bering Sea scientists… Break up the area using a grid (1 km 2 ) Take one sample from one grid Grid to be sampled chosen using a random stratified sampling method. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 17

U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 18

Samples of Pollock in 2012 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 19

Distribution of fish may change… Seasonally Yearly due to environmental shifts Temperature Food availability U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 20

What happens to the distribution of large concentrations of Pollock? 2012 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 21

2011 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 22

2010 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 23

2009 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 24

2008 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 25

2007 U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 26

Pollock like the water column – meaning their distribution isn’t associated with a habitat feature associated with the structure of the earth – such as sediment type or a rocky outcropping. But their distribution is linked to another physical element called Temperature. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 27

Fish Fetch: Survey simulation and population estimation activity U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 28

Fish Fetch – A population estimation simulation activity How to play Split into two teams of scientists Each team will be conducting a survey of the Bering Sea. Name your fishing vessel. Each team needs a: Field Party Chief - oversees operations and determines where to sample Deck Boss - sets up sampling hands out sampling gear Fish sampler - Throws sampling gear to collect sample Data recorder - Records data Data analyst - leads team with calculations U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 29

Each team begins with $150K Each survey day costs $10K You can complete one sample per day Pick a card to start your survey. Recalculate your budget. Start sampling - close eyes and toss bean bag onto grid - count, then record number of fish within grig. Remember that each sample costs one day of ship time. Pick another card after every 3 samples. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 30

Once you have spent all of your money, calculate your estimate. Sum of all samples/# of samples (# of grids) = Average. Average x total area (total # of grids) = population estimate Come back together as large group Field Party Chief reports how their survey went. U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 31

Compare results from two surveys Total budget Total number of samples Average number of fish per sample Estimate Money lost to storms Money lost to other things Did one team get a better estimate? Why? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 32

Extra credit – What is happening to the pollock biomass over the years? U.S. Department of Commerce | National Oceanic and Atmospheric Administration | NOAA Fisheries | Page 33

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