The Lives of Food Fish - Pacific Sardines and Herring

A sardine preserved on ice
A sardine preserved on ice | Source

Sardines and Herring

Sardines and herring are very nutritious and popular fish. They are both valuable foods. It's interesting to study these fish while they are alive and in their natural environment, however. They live in large groups and have some unusual behaviours.

The words "sardine" and "herring" apply to a variety of fish species that belong to the family Clupeidae. Sardines are small, silvery fish that are named after the island of Sardinia in the Mediterranean, which was once an important area for the sardine fishery. Herring are also silver in colour, but they are bigger than sardines. In this article I focus on the Pacific sardine and the Pacific herring.

Pacific Sardine
Pacific Sardine | Source

Sardines and herring are rich in omega-3 fatty acids, which are thought to have important health benefits. They seem to improve memory and mood and may also help prevent cardiovascular disease and improve arthritis symptoms.

Nutrients in Sardines and Herring

Sardines are eaten by marine animals and birds as well as by humans. They are an excellent source of protein, omega-3 fatty acids, calcium (if the bones are eaten), vitamin D, vitamin B12 and selenium. The fish are sold fresh, frozen and canned. Canned sardines are healthiest when water-packed and unsalted. Sardines are very low in mercury, an environmental poison that enters water and contaminates the bodies of fish.

Herring are also a nutritious, low-mercury food and a good source of omega-3 fatty acids. Confusingly, young herring are sometimes known as sardines.

Sardinops sagax, which is known as a sardine or a pilchard
Sardinops sagax, which is known as a sardine or a pilchard | Source

Distribution of Pacific Sardines

Sardines generally live in temperate and subtropical oceans but may also be found in estuaries. There is a freshwater species in the Philippines. The “true” sardine (Sardinus pilchardus) is also known as the European pilchard. As its name suggests, it's found in ocean waters around Europe.

The Pacific Sardine (Sardinops sagax) is found along the coasts of countries bordering the Pacific Ocean. It's found on the west coast of Central and North America from Baja California to Alaska, although its exact location depends on the time of year. Sardines migrate to find a suitable water temperature as the year progresses. The sardines off the coast of Peru and Chile are the same species as the Central and North American sardine, but a different subspecies. Pacific sardines can also be found off the coast of South Africa.

The Indian oil sardine, or Sardinella longiceps
The Indian oil sardine, or Sardinella longiceps | Source

Sardine Appearance

Pacific sardines have an attractive, elongated body that is silvery and iridescent. The upper surface is blue or green, depending on the subspecies and the angle at which a fish is viewed, while the sides and belly are silver. The fish has a row of dark spots along its side, only one dorsal fin on the top of its body and a strongly forked tail. There are no scales on the head.

Unlike most other bony fish, sardines lack a lateral line. The lateral line is a series of sense organs running along each side of a fish's body. The sense organs detect low-frequency vibrations in the water.

Sardines may reach a length of fourteen inches, but are usually about nine inches long when they are adults. They can live as long as fourteen years, but the majority of the population is younger than six years of age.

A Shoal of Sardines in South Africa

The Annual South African Sardine Run

Every year between May and July - with a few exceptions - sardines migrate along the coast of South Africa in a huge group. Eager predators include dolphins, sharks, seals, gannets, cormorants and humans. They all converge for a fantastic feast as the sardines travel northwards.

The gigantic sardine group is known as a shoal and may be several miles long. Dolphins herd the sardines into dense, dark balls of fish which make it easy for the animals to catch their prey. Sharks also herd the sardines. Sometimes the sardines are driven on to the shore where eager humans grab as many fish as they can. A dive festival is held in conjunction with the sardine run. The run is a very exciting event for both predators and observers.

The scientific name of the fish involved in the South African sardine run varies. Many sources list its name as Sardinops sagax ocellatus, making it a subspecies of the Pacific sardine. Some sources give its name as Sardinops ocellatus, however, making it a different species from the Pacific sardine.

A Pacific sardine catch
A Pacific sardine catch | Source

A Group of Sardines - A Shoal and a School

Pacific sardine groups may contain millions of fish. Fish come together for protection from predators. An individual fish is less likely to be eaten when traveling in a group than when traveling as an individual.

A group of fish is known as a shoal or school. The two words are often used interchangeably, but some fish researchers use the word "shoal" to refer to a social group of fish and "school" for a shoal in which all the fish's movements are coordinated. The fish in a school move in a synchronized fashion, with the fish suddenly changing their swimming direction in the same way at the same time. The school acts as thought it's one creature. A shoal may temporarily become a school and then go back to becoming a shoal again.

The Life of a Pacific Sardine


Sardines are filter feeders and eat plankton, which consists of tiny plants and animals moved by water currents. The sardines open their mouths as they swim through the plankton. Plankton and sea water enter the fish's mouth, pass over its gills and then flow back into the water through the opening under the gill cover. As the water flows through the gills, structures on the gills called gill rakers trap the plankton. The gill rakers direct the plankton into the esophagus, which then transports the food to the stomach.


The main breeding area for the Pacific sardines in North America is located off the coast of southern California. The fish reproduce multiple times in a breeding season. Fertilization is external. The eggs and sperm are released into shallow water, where they join. If they aren't eaten by predators, the fertilized eggs hatch in about three days.

A Pacific herring
A Pacific herring | Source

Pacific Herring

The Pacific Herring (Clupea pallasii) may reach eighteen inches in length. Most adults are around twelve inches long, however. Like Pacific sardines, Pacific herring have a blue-green upper surface, silver sides and a silver belly, and they have no lateral line. Also like Pacific sardines, herring travel in large groups and are filter feeders. Herring have a protruding lower jaw and eat mainly zooplankton (tiny animals). They spend the day in deep water and move close to the surface at night to feed.

The females lay their eggs in shallow water. The eggs stick to subtidal and intertidal vegetation, where they are fertilized by the male. The male releases his sperm in milt, a milky white liquid that colours the water. The eggs hatch into larvae after about two weeks, the exact time depending on the water temperature. A Pacific herring may live for as long as eight years if it isn't caught by a predator.

The Atlantic herring, or Clupea harengus, is very similar in appearance to the Pacific herring.
The Atlantic herring, or Clupea harengus, is very similar in appearance to the Pacific herring. | Source

The Pacific herring performs a behaviour known as "flashing". As it turns suddenly while it's swimming, its silvery, reflective body produces what looks like a flash of light. The effect is especially noticeable when multiple fish in a school flash at once.

A School of Pacific Herring

Pacific Herring in the Environment

Pacific herring play an important role in their ecosystem and have been very important in the lives of indigenous people. Many marine mammals, fish and birds feed on the herring and/or their eggs. Even łand animals such as bears visit beaches to eat herring eggs from seaweed that washes ashore. Herring spawning is time for a feast for many animals.

As a food, herring are energy-rich and nutritious. They have a short shelf life, however. Humans eat them when they are fresh, frozen, dried, smoked, salted, pickled or canned. The fish are also used to produce a meal and an oil.

In the past, herring played a dominant role in the life and culture of the First Nations groups along the Pacific Coast of North America. These groups still catch herring, as do commercial fisheries. The herring population is not as large as it once was, however. The fish are abundant in some areas but are reduced in number in other parts of their range.

Herring are so important in the food chain that a collapse in the fish stocks could be disasterous. Collapses have occurred periodically in recent times, probably due to overfishing by commercial fisheries, although there may be other contributing factors. There are other signs that some populations are in trouble, including slow return from a collapse and smaller fish size.

The Pacific Herring - A Foundation Species

Herring FRTs

Herring release gas from their anal duct in a noisy stream of bubbles. This process is used to communicate with other herring. Researchers have named the signals "Herring FRTs". FRT stands for "Fast, Repetitive Ticks". Both Atlantic and Pacific Herring make FRTs.

The bubbles are released at night when many herring are in the same area. Tests with captive herring show that the sound is produced whether or not the herring have recently fed. This suggests that the gas bubbles are not simply a by-product of food digestion. In addition, the frequency of the bubble release doesn't increase when the scent of a shark is placed into the tank holding the herring, so the bubble production doesn't seem to be a response to fear.

Researchers say that herring gulp air from the water surface. The air enters the swim bladder of the fish and is then released through an opening located near the anus. Herring have good hearing. Their sounds are thought to be used for communication between the fish, enabling them to come together in the dark and maintain contact with each other. Herring and sardines can hear higher pitched sounds than most other fish. Most marine predators can't hear the herring sounds. Dolphins and whales can, however.

Herring Sounds

The Importance of Sardines and Herring

Sardines and herring are interesting fish that play an important role in their environment. If they disappear, many animals will be adversely affected. Human collection of the fish needs to be a sustainable industry, both for our benefit and for the benefit of animals.

There is still much to be learned about the behaviour of sardines and herring and the ways in which they communicate with each other. There are probably many more interesting discoveries to be made. Though they are an excellent source of nutrients, it's sad that the fish are often thought of as only a food.

© 2011 Linda Crampton

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Comments 24 comments

A.A. Zavala profile image

A.A. Zavala 5 years ago from Texas

Fascinating hub. I've always wondered about these fish, their varieties, their consumption. Now I know!

Movie Master profile image

Movie Master 5 years ago from United Kingdom

Hi Alicia, well these little unassuming fish are a lot more interesting than I realised.

I eat them both, as they are rich in omega 3.

I thought the herring bubbles release was really intriguing.

Great hub, thanks for sharing and voting up.

drbj profile image

drbj 5 years ago from south Florida

What a wealth of sardine and herring information here, Alicia. Thank you. So herring FRT? To communicate? Wow, who knew?

b. Malin profile image

b. Malin 5 years ago

I'm probably one of those nuts who now and then likes to eat Sardines in the oil with some sweet onions...and they are Healthy! I also enjoy Herring (pickled) as well. As usual a Fun and Informative, as well as Interesting read Alicia.

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Hi, A.A. Zavala. Thanks a lot for the visit and the comment.

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Thanks for the vote, Movie Master. I eat sardines too, and herring occasionally. Like you, I want to include omega-3's in my diet. Yes, herring communication by bubbles is certainly interesting!

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Thank you, drbj. I appreciate the comment. Herring FRT's are interesting to investigate!

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Hi, b. Malin. I'll have to try picked herring - it sounds very tasty. Sardines and onions sound good too! Thanks for commenting.

writer20 5 years ago

I was surprised this morning see your hub.I used to eat Sardines in England but since coming to the U.S. I told forgot about until I saw the in Costco. I use to have them on toast, so I tried them again this way and yes they are still very tasty.

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

I agree with you, writer20, sardines on toast are tasty. I feel kind of bad eating sardines and herring because I'd like them to live, but they do contain healthy fats and other nutrients that are important for our health. Thanks for the comment.

Ingenira profile image

Ingenira 5 years ago

We can't easily buy fresh sardines here, but we get them in cans, and we love to have it on toast too !

Very informative hub, voted up !

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Hi, Ingenira. I eat canned sardines too instead of fresh ones. I like to eat sardines because they can be part of a healthy meal or can be eaten as a healthy snack. Thanks for the visit and the vote.

thougtforce profile image

thougtforce 5 years ago from Sweden

Very interesting hub about sardines and herring. Even though herring is very common where I live I have learned so much new and fascinating info about them! Great videos too!

Voted up,


AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Thank you very much for the comment and the vote, Tina. I appreciate your visit.

prasetio30 profile image

prasetio30 5 years ago from malang-indonesia

This was so beautiful hub. I love fish and I really enjoy this information. Unfortunately, I can't find Herring in my country. But Thanks for writing and share with us. Well done, Alicia. Vote up and useful.


AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Hi, Prasetio! Thanks a lot for the comment and for the votes. Like you, I enjoy fish. I think that they are very interesting animals to observe and study, and some fish are a wonderful food source.

moneycop profile image

moneycop 5 years ago from JABALPUR

alicia C was very help ful to me. last week i had a search about the fish which eat mosquito larva , we have a very good storage facility in roof to collect the rain water but , mosquitoes larva have troubled us.

at shop i gone through many fishes and to my knowledge not after reading you hub, i can buy one for my aquarium also

thanks for sharing

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Hi, moneycop. Goldfish and koi will eat mosquito larvae and they can live in garden ponds. I hope that your mosquito problem is solved soon! Thanks for the visit and the comment.

Nell Rose profile image

Nell Rose 5 years ago from England

Hi, well I have heard of people talking out of their backsides before but never fish! lol really interesting, great info, I do eat quite a lot of fish, but never knew all this, thanks nell

AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Thanks a lot for the visit and the funny comment, Nell! Herring certainly do have a strange way of communicating with each other.

Eiddwen profile image

Eiddwen 5 years ago from Wales

Brilliant as always ,I love your hubs on this series and every single one is bookmarked and I am learning so much.

Take care


AliciaC profile image

AliciaC 5 years ago from British Columbia, Canada Author

Thanks a lot, Eiddwen. I appreciate all your comments very much! I love writing hubs about animals, and it's wonderful when people enjoy reading them.

BlissfulWriter profile image

BlissfulWriter 4 years ago

Great BBC video. I love eating canned sardines. Yeah, get the water-packed or olive-oil packed ones instead of the tomato-sauce-packed one.

AliciaC profile image

AliciaC 4 years ago from British Columbia, Canada Author

Yes, I agree, BlissfulWriter - it is important to make sure that canned sardines are packed in something healthy. It's a shame to ruin a healthy and nutritious food!

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