|Length||3 ft (1 m)|
|Weight||15 lb (7 kg)|
|Social Structure||Schooling predator|
|Conservation Status||Least Concern|
|Preferred Habitat||Eastern Pacific|
|Average Clutch Size||Millions of eggs|
|Main Food Items and Prey||Baitfish, cephalopods|
|Predators||Tuna, billfish, toothed whales, sharks, sea lions, seals|
The sierra, Scomberomorus sierra, otherwise known as the Pacific sierra or the Mexican sierra, is a medium-sized fish belonging to the family Scombridae and is a part of the tribe collectively referred to as the Spanish Mackerels. It can be found in the eastern Pacific Ocean along the coast from southern California to Chile.
Like many other members of its family which also contains “true tuna”, the sierra’s body is long and fusiform and covered in small scales. They can grow up to 3-4 feet long and weigh around 15 pounds. Their bodies are a bronze-green and black color on their dorsal side, transitioning to a silver-white color ventrally. Most specimens have rows of small orange spots on their flanks, the majority of which fall below their lateral line.
The sierra has a white anal fin located approximately as far back on their bodies as their second dorsal fin, which falls just behind their sail-like first dorsal fin. They also have small pectoral fins just behind their gill slits and a series of 7-10 finlets on both their ventral and dorsal sides between their rear dorsal and anal fins and their caudal fin (tail fin).
Distribution and Habitat
The sierra is found in the eastern Pacific ocean typically between southern California and Chile. It is a pelagic species that will generally stay near the coast throughout this range, and may also be found near offshore islands or underwater seamounts. They tend to school with other sierra and fish of a similar size such as juvenile tuna. Sierra can be found near the surface, normally in no more than 50 feet of water.
Like the other members of their family, sierra are voracious predators. They will feed primarily on many small fish species such as anchovies, clupeids, and herring. They will use their speed to ambush schools of these species, picking off individuals from the group as it forms a tighter and tighter ‘bait ball’ in response.
In turn, the sierra is also on the menu for many other oceanic predators. Throughout its range, it may encounter various marine mammals such as sea lions and seals, as well as toothed whales such as orca, dolphins, and porpoises. Many sharks will also feed on the sierra, including mako sharks, blue sharks, and bull sharks. Furthermore, larger species of fish such as tuna and billfishes will also prey on sierra and other similar species when the opportunity arises. And finally, the most pervasive predator of them all – humans – will also take the highly-prized food fish both in sport and commercial fisheries.
Reproduction and Lifecycle
Spawning occurs in summer, normally in shallow waters. Like other members of their family Scombridae, sierra are broadcast spawners. Females will release up to 1 million or more eggs throughout the water column. These are released in batches during the spawning season. Males will also release their sperm in synchrony with the females, allowing for external fertilization of the eggs to occur.
Once fertilized, the embryo will float in the water as part of the zooplankton community. Here it will develop into a larval fish and eventually a juvenile sierra, at which point it will begin schooling with other similarly-sized fish. Most individuals are mature within 1-2 years and live for up to 12 years of age.
Although targeted by both commercial and sport fisheries, populations of this relatively widely distributed species remain relatively strong. Currently, it is listed as Least Concern on the IUCN Red List of Threatened Species.
Fun Facts about the Sierra!
The sierra is far from the most famous species in its family. However, there are no shortages of biological concepts and fun facts to explore by studying this eastern Pacific species.
A Lot Like the Other
The tribe Scomberomorini, to which the sierra belongs, also contains several other similar species. All of these are a part of the larger family Scombridae, generally known as the ‘mackerels’. However, this family also contains other well-known groups of fish including tuna and bonito.
Within the tribe, which is also sometimes generally referred to as the Spanish mackerels, there are several species. One of these, the Monterey Spanish mackerel (Scomberomorus concolor) occurs effectively alongside the sierra, sharing a similar range especially in the Gulf of California. Another – the Atlantic Spanish mackerel (Scomberomorus maculatus) – lives only in the Atlantic ocean despite also being similar to the Pacific species. These nuances between such similar species demonstrate the ways that the occupation of slightly different niches across a range of habitats can lead to a high rate of speciation.
Not So Simple
Whereas these differences and similarities between species are fascinating from a biological perspective, they can create many challenges from a conservation perspective. For example, the Monterey Spanish mackerel’s range has been restricted from its historic range. Currently, it is only found in the northern waters of the Gulf of California. The Pacific sierra, alternatively, is found up and down the coast to Peru and southern California. However, where it overlaps with the Monterey Spanish mackerel, the two species can be easily confused and normally occur side-by-side. They are often both marketed simply as ‘sierra’.
While the Pacific sierra’s populations remain relatively healthy, the Monterey Spanish mackerel currently inhabits only a portion of its former range. Therefore, because the species are difficult to distinguish and often marketed interchangeably, estimating population sizes and developing conservation efforts for this species has proven difficult. Indeed, the mislabeling of seafood – often intentionally but just as often incidentally as demonstrated in the case of the sierra and the Monterey Spanish mackerel – is a significant challenge to marine conservation and fishery management efforts around the world.
Most species are important to the food web for either their place at the top or the bottom of it. The sierra, in contrast, is known as a mesopredator. This means it falls in the middle of the food chain. Both predator and prey, the sierra is known both for its ability to hunt various species opportunistically. In turn, it is also a prey item for a wide variety of larger species. However, it is not the primary prey item for any one predatory species and demonstrates a high degree of trophic plasticity. Indeed, it even shares the same prey species with some of its predators. This understanding of the species as a critical trophic link is important for conservation and ecosystem-based fisheries management efforts throughout its range.