There are 7 activities in this module. Each activity will require 1-2 class periods (assuming 50-minute class periods) to complete.
This module uses the concepts of food webs and trophic levels to explore populations of marine species in ocean ecosystems. Students will explore simulated marine environments using a computer-based virtual reality (VR) data visualization tool called VES-V (The Virtual Ecosystem Scenario Viewer). VES-V displays marine environments as though one was SCUBA diving in those habitats. The numbers and types of fish and other aquatic creatures displayed in different locations in the VES-V simulations are based on actual abundances of marine creatures and how the abundances respond to a variety of conditions.
Students will explore a marine environment in VES-V. Each student will conduct research about one of the species found in that environment, determining what it eats and what preys upon it. Students will combine their data in a whole-class jigsaw activity to create a food web diagram for this marine environment.
Next, students will gather data about populations of predators and their prey in two specific ocean environments. The first case study, based in the Gulf of Maine, explores the relationship between herring and cod that feed on them. Students will collect cod and herring biomass data during “virtual dives” in VES-V. Students will determine the relationship between trophic level and biomass for herring and cod. The second case study is set in kelp forests in Monterey Bay. Students will again “dive” in VES-V to collect biomass data. The key species in the second case study are sardines, sea lions that eat sardines, and orcas that eat sea lions. Students will again collect biomass data for the species in VES-V, then compare biomass with trophic level to reinforce their understanding of the relationship between those two quantities.
Finally, students will explore an ecosystem in the Florida Keys to see how their knowledge of trophic levels and biomass can be used to help predict the supply of a commercially important fish. Students will use biomass data for mackerel, collected in VES-V, to predict the biomass of tuna which feed on mackerel. Students will then compare estimates of tuna biomass with actual data about tuna biomass to see whether the trophic level and biomass relationship is useful for making predictions. The lesson wraps up with a discussion of the future availability of fish, such as tuna, that people are fond of eating.
Modern techniques and technologies make fishing so efficient that it is possible for humans to deplete populations of marine species. People must therefore monitor and manage populations of marine creatures to ensure that they are sustainable. This usually involves placing upper limits on the number of fish or other marine species allowed to be caught each year. Government agencies, such as NOAA Fisheries, strive to set catch limits that balance peoples’ desire for fish as a food source with the need to keep fish stocks above critical thresholds that ensure sustainable populations.
Fishery management experts need data about fish populations to assess the size and health of those populations, so they can set appropriately balanced catch limits. It is impossible to count all the fish in the sea, so fishery scientists use different methods to estimate populations of marine species. Sometimes it is very difficult to get an accurate count of a certain type of species. In some cases, one can infer general trends in a population of fish based on the population levels of a different fish that it preys upon if the second type of fish is easier to count than the first. Sometimes one can get a decent estimate of population size of a predatory fish by collecting data about its prey.
Introduction: Introduce the Ocean Food Webs Module with a Big Question: “How do Individuals, communities or governments ensure that there is enough seafood for people to eat in the future?”