The Case of the Missing Sardines—An Unsolved Mystery
By “Awake!” correspondent in South Africa
“SARDINE Frenzy Hits South Coast.” So read the caption of a report in The Star of Johannesburg, July 26, 1978. The account said: “Hundreds of people armed with buckets, crates and bags, waded into the sea at Marina Beach just south of Margate to catch sardines from the large shoal which beached there early today. The beach is crowded and everyone is in a frenzy, rushing waist-deep into the waters.” The annual “sardine run” was on.
Shoals of sardines or pilchards—the two terms are to an extent interchangeable—appear regularly off the east coast of southern Africa during the southern winter each year, about July. The shoals are first spotted near the port of East London, at the southern tip of Africa. From land, the sight of thousands of seabirds wheeling and dipping into the sea at a certain spot locates a shoal. Sometimes before the main shoal appears “pilot” shoals are seen swimming ahead. The main shoals are enormous, often being several square miles in extent—countless millions of fish!
What an opportunity for fish-loving predators! In addition to the voracious seabirds and the hungry humans, the sardines are the prey of marine predators—dolphins, sharks and other large fish. They gather at the lavish feast in their hundreds. However, their attacks are limited to the outside of the shoal. The very density of the shoal prevents these piscivorous monsters from penetrating the massed millions of sardines. For larger fish to do so would result in the clogging of their gills.
Nevertheless, at times, so say the experts, the voracity and activity of the predators goad the shoal into the shore. They may also be affected by winds or the circulation of the water. Whatever the reasons or causes, part of the phenomenon of the sardine run is, at times, a spectacular stranding of shoals on the beaches. It is claimed that it is not unusual for the fish to pile up on the beach to a height of three feet (1 m). They are usually accompanied by marine “hunters,” the larger fish, who dash about excitedly in the shallow water and are caught in great numbers by local anglers.
Heading north, the giant shoals eventually pass Durban. Then an amazing thing happens. They just disappear!
Before we examine the reasons for this phenomenal sardine run and its mysterious conclusion, let us learn more about these small but prolific fish.
This is the scientific name of the sardine or pilchard (young pilchards are usually called sardines) that forms the famous “run.” It is the most abundant of all fish of South African coastal areas. It grows to a length of 10 to 12 inches (25 to 30 cm). It has a graceful shape, is coloured light and dark blue or light and dark green, is a fast swimmer and extremely sensitive to variations in the temperature and density of water.
Huge shoals are found off the coast of Namibia (South-West Africa), particularly around Walvis Bay. It is a surface-swimming fish, living in the cold waters upwelling on the west coast. From this area, apparently, some shoals move southward, around the Cape and then head north to form the Natal sardine run.
The Sardinops ocellata, of South African waters, has many relatives in other parts of the world. Notable is the Sardina pilchardus of Europe—main source of the well-known tinned sardines. North America too has its sardine, Sardinops caerulea, known as the “California sardine.” All of these belong to the herring or Clupeidae family of fish.
But why do these myriads of fish make the long, slow trip around Africa’s extremity? Why or how do they disappear so mysteriously? Is it to spawn?
To a certain extent, the sardine spawns over most of the year. But the main period is believed to be from September to February. This spawning is prolific. It is estimated that a single female can lay about 95,000 eggs! These float in the upper waters, then in a few days hatch into larvae and eventually metamorphose into minute fish.
The main spawning of the South African pilchard occurs within a temperature range of 13.8° to 16° C (56.8° to 60.8° F) off the west coast of South Africa. A mean temperature of 15° C (59° F) gives the most favourable conditions for intensive spawning. From sea-surface charts issued by the Maritime Weather Office, Youngsfield, Cape Town, it was established that the temperature of the Natal or east coast seldom drops below about 19° C (66° F). This is above the range for any extensive spawning. Considering this factor and the degree of sexual maturity of sardine-run pilchards, it seems unlikely that the motivation of the run is spawning.
Are the countless myriads of the sardine run migrating to find better feeding grounds?
Stomach samples from the shoals showed that 75 percent of the fish were empty while the other 25 percent revealed contents of 7.7 percent phytoplankton and 8.3 percent zooplankton (minute plant and animal organisms that float in the sea). The crop of plankton on the east coast is relatively low in comparison with that of the west coast.
During July 1959 and 1960, in 69 blanket hauls off the east coast it was found that there was a total absence of young pilchards. So there is no sign of the existence of a nursery ground in Natal waters. Hence, it is improbable that the huge sardine run is a feeding migration.
Why, then, do they follow that course? One possibility could well be their reaction to currents in the seas. The view is widely held that currents play a large part in directing the movements of fish. In his book Fish Migration, Harden Jones shows that fish might use a current and countercurrent system for migration. However, he also explains that fish may be carried passively, or drift, over great distances by currents, and “what may be not more than a dispersal could then have all the appearance of a true migration.”
Their Mysterious Disappearance
This has been investigated. But attempts to tag enough pilchards during the sardine run were unsuccessful. During 1959, only 69 pilchards were tagged with internal metal tags, but none were ever recovered. However, in 1960 a report from a local fisherman suggests a possible clue. In previous years he had observed large shoals moving south during the southern spring, about September. In 1958 he caught some of these pilchards and said they “are thin, without oil, and decompose rapidly after being caught.”
Do the pilchards return to the Atlantic by means of a current flowing southwestward (the Agulhas)? This is only a possibility with, so far, no factual confirmation.
Although the motivation and the conclusion of the “sardine run” are still shrouded in mystery, it is an indisputable fact that sardines are a tremendous source of food for both men and animals. These small fish weigh only about three ounces (85 gm) on the average, but yield 175 calories, 20 gm of protein and nine gm of fat. Those delicious sardines canned in oil or tomato sauce are very nutritious!
The variety of sea life is truly astounding. It reflects a Creator who not only is bountiful but also loves variety. Why, in southern African sea areas alone, a 1953 report shows there are 1,325 species of fish! There is still so much to learn about all this marine life. And this includes the answer to the question, “Why do the South African sardines make their famous, phenomenal run and then disappear?”
It is still a mystery!
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