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Food Resources and Fisheries Science

This activity builds on the content below.

The above teacher guide is a presentation about the greenhouse effect (from the original SEA curriculum). Note: the pdf has presenter notes in yellow boxes in the upper, left corner.


Earth and Human Activity

Humans depend on Earth’s land, ocean, atmosphere, and biosphere for many resources—including air, water, soil, minerals, metals, energy, plants, and animals (Fig. 1). Some of these resources are renewable over human lifetimes, and some are nonrenewable (mineral resources and fossil fuels) or irreplaceable if lost (extinct species). All forms of resource extraction and land use have benefits as well as associated economic, social, environmental, and geopolitical costs and risks. New technologies and regulations can change the balance of these factors.

<p>Fig. 1. A taro field in Hawaiʻi provides food resources to communities.&nbsp;</p><br />

The activities of humans have significantly altered the biosphere, changing or destroying natural habitats and causing the extinction of many living species. These changes also affect the viability of agriculture and fisheries to support human populations. In order to help predict the long-term environmental impacts of resource use, scientists use mathematical models. The model results help identify potential problems and suggest desirable changes in the way humans use Earth's resources.


Fisheries

Living marine resources are vital to human life (Fig. 2). In fact, the most common use of our marine resources is for food! Marine organisms are also used to make many other products, ranging from sponges to cosmetics. It is important to manage how we take and use the living resources of the ocean to ensure populations of these vital stocks remain at harvestable levels.

<p>Fig. 2. We rely on fish and other seafood for human consumption, but we must monitor to ensure we don't take too much.&nbsp;</p><br />

The need to keep fisheries healthy is not new! Over time, societies have imposed catch limits and seasonal bans on fishing and harvesting in order to help maintain healthy ecosystems and an abundance of resources. In describing the traditional, Hawaiian cultural practices of taking care of marine resources, Pelika Andrade explained that the traditional practice was about maintaining productive resources rather than about eating specific foods (watch her discussion of the ʻopihi fishery in the video below). Pelika described the need to find, "a balance and (have) a real conversation about what management, what conservation, what preservation, what pristine looks like in a global setting."



A fishery is a defined geographic area that is associated with a population of aquatic organisms (for example, fish, mollusks, crustaceans, aquatic plants, etc.) that are harvested for their commercial, recreational, or traditional (subsistence) value. Fisheries occur in both freshwater or seawater. And, fisheries can be focused on wild or captive (farmed) stocks of organisms.


<p>Fig. 3. Tuna are a type of pelagic fish often tagerted in fisheries.&nbsp;</p>

What do we catch?

A wide variety of marine life is harvested from the waters surrounding the Hawaiian Islands. Similar to global fisheries, the majority of marine life that is commercially harvested are fishes. Harvested fishes include pelagic fishes, deep-water bottom fishes, and reef-associated inshore fishes (Fig. 3).

 

Of the 25 million pounds of marine life harvested by commercial fisheries in 2005, more than 20 million pounds consisted of pelagic fishes. Of the pelagic fishes, tunas contributed more than 14 million pounds to the total catch. Other significant catches for pelagic fishes included swordfish (more than 2 million pounds), marlin species (more than 1 million pounds), and mahimahi and opah (more than 1 million pounds each).


Fishing and Fishponds in Hawai'i

In Hawai‘i, there are several important commercial fisheries. The National Marine Fisheries Service (NMFS) works with fishers and other government agencies to help ensure the sustainability of the fisheries. At the same time, NMFS works to protect turtles, birds, and marine mammals from being accidentally taken as bycatch. Additionally, the Department of Land and Natural Resources (DLNR) has a variety of size and bag limit restrictions on most of the heavily-fished species. Some fisheries use selective nets to ensure appropriate catch sizes (check out this NPR story to learn more).


<p>Fig. 4. This image of the Kaloko fish pond in Kaloko-Honokōhau National Historical Park shows details of the rock walls.</p>Ancient Hawaiians had rules regarding the take of aquatic species in history and maintained control of fisheries through the kapu system, which prohibited the harvesting of certain fish, shellfish, and algal species during critical reproductive seasons of the organisms. This conservation practice allowed the populations of these vital stocks to remain at harvestable levels by preventing overfishing, and thus ensured the survival of the people. Also, the extensive farming of fish in Hawaiian fishponds, an early form of aquaculture, created an alternate man-made fishery which eased the strain on natural stocks (Fig 4). Check out the resources below to learn more about fishponds:

NERRS: Fisheries

Loko Iʻa: Virtual Tour of the Heʻeia Fishpond!

Take a virtual tour of the Heʻeia Fishpond on Oʻahu Hawaiʻi through the Loko Iʻa App!

 

This app was funded by the National Science Foundation and developed by Dr. Judith Lemus of the University of Hawaiʻi at Mānoa Hawaiʻi Institute of Marine Biology, Marion Ano of Purple Maiʻa Foundation, the staff of Paepae o Heʻeia and in collaboration with Brian Glazer of the UH Mānoa School of Ocean and Earth Science and Technology oceanography department. For more information about the app and its release, check out this article from the UH Mānoa News.


Bycatch

<p>Fig 5. An illustration of a Turtle Exclusion Device shows how fichers can limit bycatch.</p>Although sharks are not usually targeted by fisheries, they are often caught as bycatch, and occasionally sold for food. Bycatch occurs when organisms are caught unintentionally while fishing for other species.
 Sea turtles are also frequently caught as bycatch, but there are techniques and equipment that fishers can use to decrease bycatch, such as the Turtle Excluder Device (TED), which helps expel bycatch, like seals and turtles (Fig. 5). A TED is a grid of bars that opens at either the bottom or top of a trawl net, allowing larger animals to escape after being caught in the net. Fishers should be encouraged, or required, to use these techniques. 


Monitoring

One of the critical pieces of information required to manage fish populations and prevent overfishing is having an idea of how many fish there are where they live. Although, it is impossible to count every fish, it is relatively easy to estimate the size of a population relative to other points in time. Fisheries scientists use data from fisheries and data separate from fishery catch to obtain measures of relative abundance. Fisheries-dependent methods use records kept by fishing vessels and fishers on how many fish they have caught, relative to how much effort they put into catching those fish. This is called catch-per-unit-effort (CPUE). CPUE can then be compared to previous years to determine whether fish populations are increasing or decreasing. Fishery-independent methods of measuring fish abundance usually involve scientists conducting their own fishing surveys, such as capture-recapture methods, to estimate population numbers.


Tagging and Tracking

<p>Fig. 6. A salmon is tagged on the left side of the dorsal fin to note information when this fish is recaptured.</p>In addition to knowing how many fish there are, it is important to know where the fish are, how far they roam, and how connected one population is to another. This information is important in helping scientists, resource managers, and fishermen know more about how to sustain fish populations over time. For example, knowing how big a fish's home range typically is can help inform the creation of marine protected areas (MPAs) and how many fish can be sustainably caught from a given area. Scientists use a variety of tags and genetic analysis to better understand where fish go, where fish came from, what and when fish eat, and how connected one fish population is to another (Fig. 6).

Fisheries Vocabulary Words
  • Aquaculture: refers to the breeding, rearing, and harvesting of plants and animals in all types of water environments, including ponds, rivers, lakes, and the ocean.

  • Atmosphere: the envelope of gases surrounding the earth or another planet.
  • Biosphere: the regions of the surface, atmosphere, and hydrosphere of the earth (or analogous parts of other planets) occupied by living organisms.
  • Bycatch: species caught in a fishery that targets other species.

  • Capture-recapture method: two-sample model, used solely to estimate the unknown size of a population.
  • Catch-per-unit-effort (CPUE): an indirect measure of the abundance of a target species.
  • Fisheries: areas where fish are reared for commercial purposes.
  • Fishpond: A method of fish farming in typically shallow areas of a reef flat surrounded by a low lava rock wall built out from the shore.
  • Kapu system: the ancient Hawaiian code of conduct of laws and regulations.
  • Marine Protected Areas (MPAs): protected areas of seas, oceans, estuaries or in the US, the Great Lakes that restrict human activity for a conservation purpose, typically to protect natural or cultural resources.
  • Overfishing: the harvesting of a species of fish to the point where they cannot reproduce quickly enough to maintian the population.
  • Pelagic fish: fish that live in the open sea, away from the sea bottom.

  • Renewable resource: a natural resource (such as trees and fish) that can be replenished or replaced by natural processes.

  • Selective nets: specialized nets designed to capture only specifically sized fish.
  • Substsitence: the action or fact of maintaining or supporting oneself at a minimum level.
  • Turtle Excluder Device: specialized device that allows a captured sea turtle to escape when caught in a fisher's net.

 

Representative Image: 
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.