Three species of the genus Cynoscion, commonly called seatrout, are native to the Gulf of Mexico: the spotted seatrout, the sand seatrout and the silver seatrout. The spotted seatrout, or speckled trout as they are often referred, are a highly sought after gamefish found in all of Texas' bays. The sand seatrout are a smaller-sized seatrout as compared to the spotted seatrout, but are reported as the second most commonly caught seatrout species by anglers. Many bank or pier fishermen along Texas' coastline have hooked a "sandie" only to throw it back, assuming they caught an undersized spotted seatrout. Sand seatrout are frequently caught in bays and have no bag or size restrictions in Texas. Some fishermen declare sand trout meat par with spotted seatrout as table fare. The silver seatrout, the smallest of the three seatrout, are the least pursued due mainly to their small size and are more common in the Gulf than in the bays.
Although these species are morphologically (i.e. physical characteristics and body measurements) similar, there are some characteristics that separate them. Spotted seatrout are easily distinguishable from sand and silver seatrout, having a copious amount of spots on their back and sometimes fins, while sand seatrout and silver seatrout each lack these spots. Sand seatrout and silver seatrout both occur offshore and are often referred to as "white trout" by commercial fishermen, due to their morphological similarities. Researchers at the Texas Parks and Wildlife Department (TPWD) Perry R. Bass Marine Fisheries Research Station (PRB) recently completed a morphology/genetic analysis between these "white trout". We first determined each species was genetically distinct, with no evidence of hybridization. Morphologically we were able to distinguish sand and silver seatrout by comparing the eye diameter in relation to the anal fin base length or by counting the anal fin rays (Figure 1). Sand seatrout (Fig. 1A) have a smaller eye as compared to the anal fin base length and silver seatrout have a larger eye as compared to their anal fin base length. Silver seatrout's (Fig. 1B) larger eye, as evidenced by other open water species, most likely assists with vision in the deeper waters of the gulf.
The life histories of these species are also relatively similar, but differ in their preferred habitat, fecundity, maturity, age and growth. Spotted seatrout are commonly found throughout our bays and estuaries and are capable of living up to age nine with a total length of 37 inches. Spotted seatrout are known to be spring/summer spawners, peaking in the spring, producing eggs up to almost two million in a batch, depending on female size. Based on captured spawning individuals, spawning appears to take place over grass beds near shallow channels and passes. Also, spotted seatrout, being the most temperature tolerant of the seatrout species, are reported to migrate to deeper channels and passes in order to evade the temperature extremes of the winter and summer.
Other research being conducted by PRB involves investigating the age, growth, life history and distribution of sand seatrout in Texas. Sand seatrout, unlike the spotted seatrout, are considered more as an intermediate species, living both in bays/estuaries and the offshore Gulf and are capable of living up to age three with a total length of 23 inches. PRB research coincides with prior research demonstrating that sand seatrout are found in areas of lower salinity (i.e. the upper to middle coast). Sand seatrout were found to be spring/summer spawners, peaking in the spring, and producing up to 98,000 eggs in a batch. Spawning has been reported to take place in gulf passes of bays and just within the immediate Gulf. Wind and surface water currents actually work to transport the recently spawned floating eggs into either estuarine or gulf nurseries. Sand seatrout are also known to migrate offshore to evade temperature extremes and return to the bay once the conditions are more tolerable.
Silver seatrout are the shortest-lived and least studied of the three seatrout. PRB research has shown that silver seatrout are primarily found offshore along the middle coastline in Texas (i.e. offshore of Matagorda and Aransas/Corpus Christi areas) and are capable of living up to age two with a total length of 24 inches. They are spring/summer spawners, peaking in the summer, producing up to 50,000 eggs in a batch. It is suggested that silver seatrout use gulf nurseries rather than estuarine nurseries. Silver seatrout are reported as migratory as evidenced by a low abundance of silver seatrout within TPWD Gulf sampling areas (from Gulf shoreline to nine miles offshore) during the summer and winter and an increase in abundance during the fall and spring.
All three of Texas' seatrout are similar in a general sense, however, due to specific habitat niches, some differences are distinct (i.e. genetic, adult size, morphology). Hopefully, with the assistance of this read, fishermen unfamiliar with identifying these seatrout can now better distinguish between species.