Tag Archives: Seals

Bait Ball: Have You Ever Heard of It?

A bait ball is a spherical formation that a school of fish make when they are being threatened by larger predators, such as dolphins, sea lions, and bigger fish. This instinctual behavior is a defense mechanism so that fewer fish are exposed during this feeding frenzy. When a school of fish has no protection from rocks and crevices they must use their vast numbers to their advantage. Bait balls typically do not last longer than ten minutes due to the vast amount of energy it takes to make this tightly packed ball. It is typically a fishes last ditch defensive measure because it can draw the attention of other predators like birds and sharks.

Bait Ball marlin

mackerelEach fish coordinates with its neighbor through visual site and the use of their lateral line. The lateral line is an organ located along both sides of the fishes body. Noted by faint dots along their scale, this lateral line can sense subtle pressure changes in the water and help direct them instantaneously.

Here at Catalina Island you can see a bait ball almost everyday, in varying sizes and species. Here are the most common species of fish that make up bait balls around Catalina Island.

Bait Ball sea lion feeding

Pacific Sardine:

  • distinctive flashy quality
  • release air bubbles as they swim
  • freckles on back
  • greatest body width underneath pelvic fin

Northern Anchovy:

  • appear glittery or sparkly
  • random solitary fish open their mouths wide and flare their gill covers in order to feed
  • dark on back with no markings
  • jaw shifted farther back
  • elongated body that is straighter and thinner than sardines

Jack Mackerel:

  • often hover motionless as if they were frozen,
  • can mix in with other species of fish
  • lateral line bends down due to longer pectoral fin
  • back is blue green or brassy brown
  • symmetrical dorsal and anal fins

Sources:

https://www.nwf.org/Magazines/National-Wildlife/2017/Feb-March/Conservation/Forage-Fish

https://daily.jstor.org/how-do-fish-schools-work/

https://www.sunshinecoastdaily.com.au/news/incredible-bait-ball-fish-try-intimidate-predator/3182035/

https://ocean.si.edu/ocean-life/fish/bait-ball

https://www.pierfishing.com/jack-mackerel/

Video Content from Gretchen Beehler and Anthony Julien

Harbor Seals 101

Have you ever noticed a speckled mammal trying to camouflage into rocks along the California coast?! If so you may have spotted a harbor seal! Harbor seals are marine mammals that belong to a group called pinnipeds (meaning “fin-footed”). Harbor seals are found north of the equator along the Atlantic and Pacific Oceans. They range from Alaska all the way down to Mexico, and are commonly found in coastal waters, rocky islands and on sandy beaches.

harbor seals

(Harbor Seals along a coastline.)

Harbor Seals typically have spotted coats in a variety of shades that range from white, dark browns, and even black. They range around 5 to 6 feet in total length and have very small flippers. They move along on land by flopping around on their bellies. They also lack earflaps, and have internal hearing. A fatty tissue known as “blubber” helps to keep them warm. They also have very large eyes that help them to see in dark, deep water.

A baby harbor seal is called a pup. When pups are born they can swim at birth and sometimes when they are tired they will even ride on their mother’s back! Pups are weaned around four weeks old and females will mate and give birth to one pup every year. Harbor Seals can reach a lifespan of up to 30 years!

The harbor seal spends about half of its time on land and the other half in water. They can dive up to 1500 feet and hold their breath for up to 40 minutes! An average dive however is typically shallow and lasts around three to seven minutes. Unlike humans, they breathe out before diving deep into the water. They then use oxygen that is already in their blood and muscles while underwater. Their heartbeat actually slows from around 100 beats per minute to just 10!

 

harbor seals 2

(Harbor seal lounging on a sandy beach.)

The diet of a harbor seal consists of flounder, sea bass, cod, squid, and octopus. They actually use their whiskers to help them hunt and navigate by sensing pressure waves from fish and underwater objects!harbor seals 1(Left: Harbor seal using its long whiskers to help it hunt for prey.)

All in all, the harbor seal is one charismatic marine mammal. From their cute appearance to their smooth swimming style, these seals have earned their cuddly reputation. Go out to the beach now and try to find one of these marine mammals on a snorkel so you can truly see their beauty!

Written By: Brooke Fox

 

References:

http://naturemappingfoundation.org/natmap/facts/harbor_seal_k6.html

http://www.marinemammalcenter.org/education/marine-mammal-information/pinnipeds/pacific-harbor-seal/

http://www.seadocsociety.org/harbor-seal-facts/

Seal vs. Sea Lion

When discussing the difference between the seal vs. sea lion we can find five main differences that have to do with their anatomy and character traits. The first difference between the seals and sea lions that we will discuss is the shape of their bodies and front fore flippers. The California Sea Lion as pictured in the video have two large fore flippers that they use to help walk on land as well as swim in the water. They are typically slimmer and do not have as much fat as the seal as well. While the Elephant Seal, as pictured and other common seals such as the Harbor Seal, have much smaller fore flippers only used to help swim. They do not use their flippers to walk on land rather “wiggle” their large bodies to help them move. The next notable difference between seals and sea lion has to do with their face and snouts. Sea lions have a large pointed snout, giving the sea lion the look of a slimmer face. While the seal has a compacted snout, giving it a larger and rounder head and face. To finish up the anatomical difference between the two we look at their ears. Sea Lions have large “floppy” external ears while seals have internal ears. Moving on to the traits and habits of seals and sea lions we typically see two main differences. The first is how these two move in the water and surface for air. Sea lions do something called porpoising! Porpoising is when these sea lions will jump completely out of the water in similar fashion to that of dolphins. On the other hand seals will swim completely submerged under water and will come up to take a breath every 5 or so minutes. When they do they will only stick out their head and observe their surroundings. This act is called periscoping. And the final difference between seals and sea lions is the sound that they emit. Sea lions will “bark” like that of dogs while seals will emit a “snarl”. These conclude the five main differences between seals and sea lions. While there are other differences between the two, these are the most notable and talked about differences.

Here on Catalina Island we often see juvenile pinnipeds (seal and sea lions) wash ashore on our beaches. One pinniped in particular is the Northern Elephant Seal. These seals are typically pups that are being weaned from their mothers. When the pups are born they are around 4ft long and weigh about 75lbs (pounds). They will suckle for about 28 days and gain an average of 10lbs (pounds) a day! These elephant seals have some of the richest milk of any pinnipeds in the world averaging about 50% of the milk being actual fat. These elephant seal pups will quadruple in weight from the original 75lbs to an astonishing 250 to 350lbs!! At the end of the suckling period the mother elephant seals will abandon their pups to return to feed leaving these pups to fend for themselves and come ashore. As these pups come ashore to various different locations they will lose some of their weight gained from their mothers and learn how to fend and feed for themselves. We also see juvenile sea lion pups come ashore as well. These pups are usually moved out of their rookery leaving them to feed and fend for themselves as well. If you every see a seal or sea lion pup washed ashore it is best to let them rest and not interfere. These are crucial stages for these animals and any help given to them could cripple their growth and ability to feed for themselves.

Northern Elephant Seals

Did you know? Northern Elephant seals have one of the longest mammal migrations on the planet! They spend almost all their time venturing across the ocean, specifically in the North Pacific range, and travel from their rookery sites out to the continental shelf and back again twice in one year. This migration is done twice due to breeding and molting events, spending only about one month each time on the beach before returning back to the open ocean.

These animals are truly amazing, possessing some pretty impressive abilities. The longest recorded dive of an elephant seal was around 2 hours, and the deepest dive was recorded to be around 5,000 feet. These silly seals get their name from the gigantic nose that is grown by males at sexual maturity. This nose, or proboscis, helps the male by allowing him to make loud trumpeting echoes and this helps attract females as well as to assert dominance over smaller males. Males usually arrive at the breeding beach, or rookery, around January to scout out a spot on the beach. Then the females arrive and will mate as well as give birth to their newborns that they have been carrying since the previous year. The females will stay on the beach nursing their newborn pup for around 28 days before heading back into the water and leaving their pups to fend for themselves. Pups will band together and slowly learn how to catch food in tide pool areas before easing their way into the open ocean. The California coastline holds some of the largest elephant seal rookeries, where they return year after year for mating, birthing, and a catastrophic molt in the summer. During this catastrophic molt, they will shed their first layer of hair and skin, which is quite the sight for an unknowing onlooker! There are many great vistas and protected areas where the public can view these glorious seals in their natural habitat, but don’t get too close! Males can weigh in at a whopping 5,000 pounds, and will charge when threatened. The most miraculous thing about these elephant seals isn’t their size, stamina, or diving abilities. They were able to bounce back from the brink of extinction, with less than 100 individuals left by 1910. They were hunted for their rich blubber, but with the proper protection, are now thriving with an estimated population of around 200,000.

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