Sardines

The ocean is one of the few remaining natural systems where wild species are harvested by humans on a grand scale. Just as marine birds and mammals have taken advantage of bountiful herring/sardine schools along northern coasts, humans in marine environments have long depended upon this resource for sustenance. Atlantic herring fisheries existed as early as 240 A.D. Nearly every culture along North Atlantic coasts, from historical tribes and settlements to modern communities, have fished for herring/sardines.

Here is where you can learn as much as you would like. We have set up this section for you to get a better understanding of what you are eating and how it gets to your table.

Sardine’s Life Cycle

Sardines, or pilchards, are a group of several types of small, oily fish related to herring (of the family Clupeidae). Sardines were named after the Mediterranean island of Sardinia, where they were once found in abundance.

The terms sardine and pilchard are not precise, and the usual meanings vary by region. One system suggests that fish shorter than 15 cm (6 in) in length are sardines, and larger ones, pilchards. The International Codex standard for canned sardines cites 21 species that may be classed as sardines; FishBase, a comprehensive database of information about fish, lists at least six species called just pilchard, over a dozen called just sardine, and many more with the two basic names qualified by various adjectives.

As a food, sardines are rich in minerals. They are commonly sold canned, but fresh sardines are often grilled, pickled or smoked.

Herring are pelagic, fish that inhabit the open sea and offshore banks for most of their lives. Young juveniles (brit) are numerous in inshore waters along the coast in the spring and summer. Adults migrate across hundreds of kilometers of ocean during their life span. In the winter, schools of migrating Atlantic herring can join forces, forming massive expanses of fish as far as the eye can see. In the North Atlantic, people have observed herring schools measuring up to 4.5 billion cubic meters (over four cubic kilometers) in volume, with densities of up to one fish per cubic meter.

Larvae

Herring eggs that do not succumb to low oxygen levels or hungry predators hatch in about 7-10 days. Early development can take place over a wide salinity range, with the rate of development largely determined by water temperature.

Like many organisms, the larval and adult stages of herring are very different in appearance. Larval herring are elongated, transparent and entirely lacking scales. Larvae are approximately 5 to 7 mm long when they hatch and carry a yolk sac that provides a mobile food reserve.

As they deplete their yolk reserve (+/- 10 days), their tiny mouthparts develop enough to allow them to capture and swallow small prey. The transition to feeding in fish larvae is considered a critical period in which mortality is catastrophically high.

Larvae are weak swimmers, but are able to lunge at tiny larval plankton and eggs drifting nearby. Larval herring feed on a variety of tiny plankton. They can attack and fit in their mouths the eggs and larval stages of copepods, clams, barnacles, and shrimp.

After hatching, the journey of the pelagic larvae is primarily at the mercy of the prevailing currents, tides and wind. Depending on environmental conditions like water temperature, the larval stage lasts from 3 to 11 (typically 6) months.

Not surprisingly, mortality levels are high during this vulnerable life-history stage - the odds of survival are stacked against these odd-looking transparent drifters. The pelagic phase is long and the young fish are potentially dispersed over a huge geographical area. Some researchers estimate that only about 1% of herring larvae survive to become juvenile fish.

Juvenile

In the spring, larvae metamorphose into juvenile herring. Scales form, their bodies begin to deepen and flatten, and they are no longer transparent, taking on the silvery blue-green colours characteristic of adults. In short, they begin to look like herring.

The young herring, now termed brit, are about 40 mm long. The brit herring migrate towards shore, collecting in dense schools near the surface.

Aggregations of brit herring enter shallow bays and inlets, where they migrate vertically in the water column in response to light cycles. Dispersed throughout the water column during the day, they collect in surface waters at night to feed on their zooplankton prey. In the late summer and fall, when adults are migrating onshore to spawning grounds, the brit move offshore to spend winter close to the bottom.

Brit serve as an important food source for many predators and, as a result, are commonly spotted hiding under docks and piers. Mackerel, striped bass and many sea birds, including puffins, gulls, and terns, focus their attention on brit herring schools.

Adult

Atlantic herring mature when they reach three to four years old, at which time they measure approximately 23-26 cm (9-10 in) in length. In the Gulf of Maine, they can live for 12 years or so and reach a maximum length of approximately 40 cm (15 in) at a weight of about 680 grams (1.5 lbs).

Atlantic herring migrate over great distances of open sea. They migrate to feed. They migrate to spawn. They migrate to their winter grounds. Researchers and fishermen alike have studied the spawning migrations of herring in the Gulf of Maine.

In general, the spawning pattern of herring conforms to the typical triangular migration pattern common in pelagic schooling fish. Adults migrate against currents from feeding grounds to spawning grounds. Larvae drift passively away with currents, and juveniles eventually swim back out to join adults at feeding grounds

What do they eat?

Herring survive entirely by feeding on plankton - the tiny drifters of the ocean. There are two basic types of plankton: phytoplankton (plants) and zooplankton (animals). The zooplankton community, comprised of invertebrate and fish larvae, as well as many species that remain drifters for life (holoplankton), is thought by some scientists to be the biggest source of protein in the world's oceans and is, not surprisingly, an important food source for many organisms. Although herring are opportunistic feeders, they feed primarily on small holoplanktonic crustaceans called copepods.

Herring feed at night in the upper water column, following the massive vertical migrations of zooplankton that inhabit deep waters by day and surface waters by night. Research has shown that herring feed on zooplankton in several ways. Much like the way a whale strains zooplankton from the water with its baleen plates; herring are able to use their gill rakers to filter-feed. Herring can also visually detect larger prey, such as an individual copepod or a mysid shrimp, and execute directed attacks on these targets.

Species

There are several species of fish in the herring family. Typically, herring are small, streamlined, schooling planktivores, or plankton-feeders. The nearly 200 true herring species in the family Clupeidae, share several distinguishing characteristics. Herring are silvery fish with a single dorsal fin, no lateral line, and a protruding, bulldog-like lower jaw.

Unlike many other fish, true herring have soft fins that lack spines, although some have pointed scales that form a saw-toothed "keel" running along the belly.

Streamlined for swimming, the herring body is relatively deep and flattened laterally (side-to-side), with a distinctly forked tail (caudal fin). Turn an Atlantic herring sideways and you could probably slide it under your closet door. The compressed body and silvery scales serve as camouflage in the open waters of the ocean, scattering light and helping to conceal herring from predators attacking from the deep.

In general, species of the herring family are characterized by large spawning migrations, with schools of fish traveling round trip distances of up to 3000 km (1800 mi). Within the boundaries of these common traits, the many species of the herring family are actually quite distinct from one another in terms of size, appearance, behavior, and distribution.

Atlantic herring

Norway brisling

In the North Pacific Ocean the Pacific herring, Clupea pallasii, closely resembles our Atlantic species, Clupea harengus. While morphologically similar, there are some differences in their life histories. Atlantic herring spawn in the spring and fall whereas Pacific herring are strictly spring spawners. Pallasii is the Latinized last name of Petrus Simon Pallas, a Russian naturalist and explorer who first described the Pacific species during his travels in the North Pacific.

Harvesting

The Fixed Gear Weir Fishery

The fixed gear weir fishery still exists today, primarily along Grand Manan Island and New Brunswick's Bay of Fundy coast. Modern herring weirs are similar to the early Native American versions. They consist of a fence of long stakes driven into the ground with nets arranged in a circle or heart shape. The bottom stake rises just above low tide level and is lashed to a top stake that rises several feet above high water. Securely fastened to the weir stakes from top to bottom is a massive net.

Swimming along the shore at night, schools of young herring bump into the lead line or fence and are directed towards the shore to enter the weir through its open mouth. Once inside the weir, the herring are unable to exit and swim in a circular pattern. Fishermen check their weirs at sunrise, using boats and manpower to purse seine the trapped herring from the weir. From here, the herring are transferred to larger boats called herring "carriers" which bring the catch to nearby processing plants.

Purse Seining

Purse seining is the process of catching schooling fish near the ocean surface by circling them with a net. Once the fish have been encircled, a wire (purse line) running through the bottom of the net is winched tight to "close the purse" from below. Purse seining for herring can be especially tricky as the entire process is run in the dark of night when herring swim to the surface to feed on rising phytoplankton. No lights are used until the seine is closed.

The top of the net stays at the surface, buoyed by a float line. The bottom of the net is connected to the purse line by large, metal clips called rings. These also act as weights that sink the net to depths of up to 100 meters.

When the net is in place, a winch on the deck of the seiner pulls in both ends of the purse line, closing off the bottom of the seine net like a giant drawstring.

Once the bottom of the seine is closed, preventing the herring from escaping, one end of the seine net is run through a large, hydraulically driven power block located at the top of a crane. As the net is lowered through the powerblock, it is stacked on deck in preparation for the next set. This process slowly pulls the portion of the seine net still in the water shipward, forming a concentrated pocket of herring.

A submersible pump is then lowered into the pocket, pumping fish to a dewatering box, then to holds below the deck or to herring carriers waiting nearby. The entire process is repeated as many as five times in a single night with as many as 200 tons of fish captured during each set.

Mid water trawling

Mid-water (pelagic) trawling is the process of deploying and towing a net at a chosen depth in the water column to catch schooling fish such as herring and mackerel. This differs from "bottom" (benthic) trawling in which a net is dragged along the ocean bottom where fish such as cod, haddock, and flounders live.

On the east coast of North America, fishermen typically use large mesh at the front end of mid-water trawl nets. This allows for very large net openings compared to wide, but vertically narrow bottom trawls. The large front end of the net herds schooling fish toward the back end, where they are trapped in the narrow "brailer". Independently swimming fish leave the trawl net at will.

To set the trawl, net is unrolled from a net reel until completely in the water. The net is held open along the bottom with 450-2200 kg (1000-5000 lbs) of wing-tip weights and foot chain under the foot rope, which connects the wing tips. The sides of the deployed net are spread horizontally with two large metal foils, called "doors", positioned in front of the net. As the trawler moves forward, the doors, and therefore the net, are forced outward. Alternatively, two vessels working together as "pair trawlers" can pull a single net between them, enabling the use of a large net due to reduced drag from not using doors to keep the net open.

Once off the reel, the net is attached by cable to winches on each side of the ship. Net depth and position are controlled using both speed of the boat and amount of wire released. A good analogy is flying a kite where wind speed and line released determine height. However, the captain of a trawler cannot see what is happening in the net hundreds of meters behind and below the vessel. They must rely on an array of sophisticated electronics, such as sonar units attached to the net, to relay information about the net's shape, how the fish are schooling, and how many fish have become entrapped in the net.

When the captain determines it is time to haul back (as little as 10 minutes or as much as 8 hours after setting the net), the long tow cables are winched in and the net is spooled onto a large net reel. A pump is attached to the end of the net and fish are pumped into a dewatering box and into holds below deck. A few trawlers bring the full net along one side then hoist small sections of the net for release on deck and into holds. This process is repeated until the net is emptied.

Processing

Delivery

The fish arrive at the plant either directly on the vessels, by sardine carrier or by truck and are pumped into the plant using large vacuum pumps designed for handling fish. Once in the plant, fish are transported to the grading room, where they are graded for size and flumed to holding tanks, where they are held in ice and brine. The salt water ice slurry refrigeration method insures that the fish are as fresh in the can as just caught. The temperature is held around 0°C (32°F) and quality control inspection continues at every step of the process.

Packing

From the holding tanks, the fish are transferred to the various packing and cutting lines as required. Traditional hand packing, semi-automatic packing, and in some plants fully-automated packing lines are used. On the hand packing line, the packers use scissors to remove the head and tail and place the cut fish into the can. With both the semi-automatic packing line and fully-automated line, the fish are placed in pockets, the heads and tails are removed by machines and the cut fish are placed in cans. The heads and tails are not wasted, they are processed into fish meal and oil that is used in a number of other industries.

Pre-cooking

Cans containing fish are placed onto racks. Full racks are loaded into carts, which are then placed into a pre-cooker that uses steam to cook the fish, reducing the moisture content and firming the fish. The carts are removed from the pre-cooker, tipped to drain the water from the cans and then cooled.

Seaming

The cooked cans are taken out of the racks and placed onto the seaming line where other ingredients such as sauces are added. The lid is placed on the can and hermetically seamed or sealed, conveyed to a can washer to ensure can cleanliness and then transferred to the retorts.

Retorting

The retort is a high pressure vessel used for cooking and sterilization. The canned product is cooked in the retorts for 45 to 60 minutes, depending on the product, at a temperature of 115°C (240°F). Upon completion the cans are removed, drained and cooled before handling. It is during the retort stage that the bones in the sardines are softened.

The sardine canneries in Maine and New Brunswick almost, exclusively process young Atlantic herring. In other locations, however, a can labeled "sardines" may contain an entirely different type of fish. The Pacific sardine (Sardinops sagax), or pilchard, is the fish that inspired "Cannery Row" in Monterey, California, immortalized by American writer John Steinbeck. While they share the same family (Clupeidae) and sometimes the same name on a can label, Atlantic herring and Pacific sardines are two distinct species.

Regulations and by-catches

The North Sea herring is managed according to the EU-Norway Management Agreement from 1997, revised in 2004. Quotas are set for the directed fishery and for by-catches in other fisheries with the aim of minimizing the by-catch of immature fish. The agreement sets limits for maximum fishery mortalities (0.25 for adults and 0.12 for juveniles) when the spawning stock is above 1.3 mill tons (Bpa). The revised agreement includes a TAC (total allowable catch) change limit of +/-15%.

The EU has a quota for by-catch of herring in the industrial fisheries while by-catches of herring taken in Norwegian fisheries are allocated against the quota. Norway has 29% of the annual TAC. Part of the international catch control system has not been fully efficient, and unreported catches in excess of quotas have been revealed for the years 2002-2004. International efforts are made to solve these problems.

Content provided by:

Gulf of Maine Research Institute