Fish – Discover-Nature

The Ocean Deep

Seventy percent of the Earth’s surface is under the ocean, and only a small portion is in shallow water along continental shelf areas. The ocean is divided into five zones; the sunlight zone, above 650 feet; the twilight zone, extending to 3300 feet; the midnight zone, down to 13,000 feet; the abyssal zone, down to 21,300 feet; and the hadal zone, extending to the bottom of the ocean. Below 3,000 feet, no light penetrates from the surface; the water temperatures are freezing; and oxygen levels are very low. The pressure exerted on any surface at sea level is 14.7 pounds per square inch (psi), and humans can withstand three to four times this amount, or 45 psi to 60 psi. At 3,000 feet deep, the pressure is 1,345 psi.

^{Delta submersible by Robert Schwemmer, CINMS, NOAA, Oct 2010}

Pressure keeps sea water from becoming solid ice, even when it is at freezing temperatures. It also makes exploring the ocean difficult, requiring special submersible vehicles. Everything moves more slowly under pressure, and a submersible can take an explorer deep into the ocean given enough time and oxygen. Deep sea creatures can survive because the structure of their bodies is lean and contain no air spaces. Let’s take a look at a few of the wondrous creatures that live in these habitats.

^{Humpback anglerfish by August Brauer in Public Domain}

In the darkness of deep areas, many species find food and mates by touch. Others may use bioluminescent communication – the ability to create light from a chemical reaction between luciferin and oxygen within an organism’s body. Lights show up as spots of various colors on different parts of the body and may be used for attracting a mate, confusing a predator, or attracting prey. Lanternfish have several spots located on their heads, undersides, and tails. Female anglerfish and dragonfish have a shaft that protrudes from their head out in front of their mouths with a glowing tip attracting prey within striking distance. Gulper eel use the lighted tip of their tail as a lure to attract a meal.

^{Tripod fish by NOAA Okeanos Explorer Program, Public domain, 2010}

^{Fangtooth fish by Sandra Raredon-Smithsonian Institution, Public domain}

Tripod fish have two pelvic fins and a tail fin that are elongated and can be filled with fluid to stiffen them, allowing the fish to stand on the ocean bottom while conserving energy. Two long, wavy pectoral fins act as arms to detect prey floating or swimming by and push the prey toward their mouths. Fangtooth fish is another species that can detect vibration and nearby movement. This species is only six inches in length, but have the largest teeth in proportion to their body size of any fish in the ocean. The long lower fangs fit into pouches in the roof of their mouths so their teeth do not pierce their brain cavity.

^{Dragonfish teeth array by UC San Diego Jacobs School of Engineering, May 2019}

The dragonfish, another small fish about six inches long, has a frightening array of teeth located on its jaws and tongue. Their teeth are transparent and their bodies are black, making them impossible to see even in depths where there may be some light. The jaws are loosely hinged, allowing the fish to open its mouth wider than normally hinged jaws would allow. Prey swimming nearby may not notice the wide opening, nor be able to detect the transparent teeth, making the dragonfish a top predator of invertebrates, squid, and shrimp. In addition, when biting, they inject a highly toxic poison to paralyze and kill their prey. This toxin can be dangerous to humans getting bitten or attempting to eat this species.

^{Giant spider crab by Michael Coghlan, Jan 2014; Gulper eel by Claf Hong, Mar 2005; Lanternfish, Myctophum punctatum1 by Emma Kissling}

Some fish practice diel vertical migration, a pattern of movement where a species feeds near the surface at night and moves back into deeper waters to rest during the day. Lanternfish come up to feed on zooplankton and fangtooth fish feed on squid in shallow waters. Some species, including anglerfish and gulper eels, have elastic-like skin for their mouths and stomachs. Mouths can be opened extremely wide to swallow prey larger then themselves. The food is contained in a similarly elastic stomach which shrinks slowly as digestion progresses. Several different species of spider crabs roam the ocean depths scavenging for meat or plant material that falls to the bottom.

Deep-sea animals are seldom seen, but are not immune from climate change and human impacts. Scientists continue to study changes in deep-sea food webs caused by overfishing, ocean acidification, and expanding low-oxygen zones. Learn more about the habitat and species of these areas at the Jurica-Suchy Nature Museum at Benedictine University or your local nature museum or aquarium.

Illinois State Symbols, pt.2

Last week, we learned about state symbols covering many of the natural wonders found in Illinois. The following paragraphs describe the state symbols for the animals that have earned recognition.

In the early 1900s, the first forest preserves in the nation were in Chicago setting aside rare habitats that would protect animal and plant diversity. Over 94% of Illinois land areas are considered rural, including 1.4 million acres of wetlands. The Illinois State Fish, the Bluegill, Lepomis macrochirus, is found in lakes and ponds and was selected by schoolchildren in 1986. Also known as bream or brim, the name refers to the bright blue gill covers sported by the male.

Eastern tiger salamander, Ambystoma tigrinum, by John P Clare, Apr 2013

The State Amphibian is the Eastern Tiger Salamander, Ambystoma tigrinum, the largest terrestrial salamander in Illinois. This State Amphibian and State Reptile were voted on by citizens in 2004 and approved by the Illinois General Assembly in 2005. It has a large head and dark body with irregular yellow blotches. It can be found everywhere in the state, although it is uncommon in large agricultural areas.

Painted turtle by Victoria Pickering, May 2020

Eastern Milk Snake, Lampropeltis triangulum, by Peter Paplanus, May 2019

There are two reptiles recognized in Illinois. The State Reptile is the Painted Turtle, Chrysemys picta, a species found in all aquatic habitats in Illinois. It is dark olive with yellow, red, or orange markings covering the plastron, forelegs, and both sides of the head. In addition, we have a State Snake, the Eastern Milk Snake, Lampropeltis triangulum triangulum. Its body is gray covered with large brown blotches with black borders. Milk snakes average 24″-43″ long, and live in fields, woodlands, and rocky areas. When agitated, the snake will vibrate its tail and hiss before striking. They are constrictors that feed on small mammals.

Monarch, Danaus plexippus, on swamp milkweed by Anita Gould, Aug 2005

Pollinator species are important to the agricultural industry. Plants of all kinds require pollination in order to set seed. Insects are one of the most important groups of pollinators. Butterflies, bees, wasps, flies, ants, beetles and many more all feed on nectar offered by plants. In the process, they collect pollen on their bodies, sometimes to eat and other times inadvertently as they push through the flower to obtain nectar. Pollen is then transferred to other plants the insect visits. The State Insect is the Monarch Butterfly, Danaus plexippus, chosen by schoolchildren in 1975. Monarchs lay eggs and feed on many of the state’s native milkweed species. The butterfly’s orange coloring is a warning to predators not to attempt to eat a monarch which consumes, processes, and stores toxins from milkweed plants for its own defense.

Cardinal, Cardinalis cardinals, by Marcel Milliard, Dec 2020

White-tailed deer in corn, Matthew Paulson, Jul 2014

The State Bird is the Northern Cardinal, Cardinalis cardinalis. Selected by schoolchildren in 1929, the cardinal beat out several other choices including bluebird, meadowlark, bobwhite, and oriole. The cardinal, a medium-sized songbird, is known for the males’ bright red feathers. It prefers the forest edge where it can enjoy both prairie and woodland resources for hunting and shelter, but is often seen in backyards. The State Animal, White-tailed Deer, Odocoileus virginianus, also enjoys living along the forest edge. Selected in 1980, deer have some amazing abilities. They are able to run at 40 miles per hour and jump over a 9-foot high fence. They are excellent swimmers, traveling 13 miles-per-hour in the water. Native Americans and settlers both heavily relied on deer for buckskin clothing and food.

State symbols are representative of items and species that are present in our state. Take the opportunity to observe these natural wonders on your next outdoor adventure.

Chinook Salmon

At this time of year, many species are migrating south to spend the winter months in warmer climates. But, a few species are moving north including the Chinook salmon, Oncorhynchus tshawytscha. The largest species of Pacific Ocean salmon, they are blue-green on the head and back and silver on the sides. Their tails, backs, and upper fins have black spots, and the tooth gum line is black. Salmon average three feet in length and weigh thirty pounds, but can grow past five feet and 110 pounds.

Chinook salmon, sometimes known as king salmon, are native to the northern Pacific Ocean and freshwater streams and rivers in the Pacific northwest. They are born from eggs laid in autumn’s cool waters that hatch in springtime when those waters start to warm. Young salmon feed on insects and small crustaceans in freshwater habitats until they become adults between one and two years of age. An anadromous species, meaning they live in both freshwater and saltwater habitats, as adults, they travel downriver to the ocean, where they will spend the next one to five years following the warmer ocean currents, eating a diet of nutritionally-rich prey including herring, sandlance, and squid, allowing salmon to reach their large size.

Oncorhynchus tshawytscha, Chinook salmon by Dan Cox, USFWS 2013

Salmon are also known as semelparous, meaning they spawn once and then die. As salmon reach maturity, they return in autumn to the rivers where they were born. Females dig a nesting hole, called a redd, in which she deposits 3,000 to 14,000 eggs. Males fight to be the one that pairs up with each female and fertilizes her egg nest. A benefit to being big is that larger females lay more eggs and dig deeper redds. A deep nest protects eggs better by not exposing them to faster, surface water. Both parents guard the eggs for the first few weeks, but the parents will die before winter, months before the eggs hatch.

Oncorhynchus tshawytscha, Chinook salmon by Mike, iNaturalist

Returning salmon and their eggs offer a buffet for more than 125 species that depend on them as a food source just before winter. Marine mammals including whales, orcas, sea lions, and harbor seals hunt large schools of salmon as they converge on the Pacific northwest coastal areas. As salmon enter the river systems, they attract eagles, seagulls, herons, kingfishers, murres, and puffins. A great variety of land mammals also make their way to the waterways including bears, wolves, minks, martens, weasels, and fox. Shorebirds wade into deep water to snack on any eggs that may escape a redd. Migrating birds on the Pacific flyway feast on salmon that are dying after spawning. Insects feed on the decaying bodies, and in turn, are food for the smaller birds migrating south.

Chinook Salmon (Oncorhynchus tshawytscha) spawning in Los Gatos Creek by Robin Agarwal, 2020

Chinook salmon populations have declined in recent decades and some populations of Chinook salmon are federally listed as endangered. Loss of snowpack and shrinking glaciers have reduced the amount of water in streams and rivers. Along with shallower waterways, warmer summers are raising stream temperatures leading to habitat where parasites and disease grow and attack more easily. Severe storms and forest fires contribute to less undergrowth and more soil eroded into rivers causing siltation that constricts the passage of water and river inhabitants. Supporting improvements in land use practices and saving habitat will greatly benefit Chinook salmon as well as the many other species they live with.