pinfish underwater

FWC photo

Most of us never think about them beyond their use as bait, but pinfish and other forage species have complex life cycles.

When it comes to catching fish, you have to think like one. And, if you want to catch fish with live bait, you’ve got to feed them what they eat. Some of the top bait fish for catching inshore fish are pinfish, whitebait and greenies. But what do you know about the life of these fish species?

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Pinfish (Lagodon rhomboides) are a pretty common baitfish known for their sharp pin-like dorsal spines. As any angler knows, pinfish are important prey for many economically important fish, including grouper, snapper, spotted seatrout, redfish, snook, ladyfish and flounder. They are also very hardy, tolerating a wide range of temperatures (from 50 to 95°F) and salinities from true freshwater to full saline ocean water.

Pinfish live up to seven years and become sexual mature at one to two years of age, around 4.5 inches or larger. From late fall to early winter, pinfish migrate offshore to spawn, although evidence of spawning inside Tampa Bay has also been documented. Females carry an average of about 20,000 eggs and likely spawn several times within a single spawning season.

Pinfish larvae are transported into estuaries by ocean currents. In Tampa Bay and Choctawhatchee Bay in the Panhandle, a study found that post-larvae (less than a half inch) settle in both shallow areas (less than 5 feet deep) and deep-water areas 5 to 12 feet deep) within one month of spawning. In Charlotte Harbor, however, they only settle in shallow water areas. One to three months after showing up in Charlotte Harbor’s shallow areas, baby pinfish begin to appear in the deeper areas.

In Charlotte Harbor, the same study found a positive correlation between young of the year recruitment and higher sea surface temperatures. This could mean increased temperatures favor hatching success, larval growth, or both. Or, temperature may affect transport of pinfish larvae into the estuary. This same correlation was not found in Tampa Bay or Choctawhatchee Bay.

Pinfish are voracious predators and feed on an assortment of prey over the course of their development. Their dietary shifts appear to be related to changes in mouth size and tooth structure. Pinfish are sight feeders and therefore feed little at night.

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Scaled sardines (Harengula jaguana), better known as whitebait, are fast-growing, short-lived marine and estuarine schooling fish, commonly found over sand and mud bottoms and on and around seagrass meadows. They are generally found in estuaries from spring through autumn and prefer higher-salinity waters.

Scaled sardines grow more than a half inch per month and live just over one year. They become sexually mature when they are about 3.5 inches in length and spawn offshore, typically 3 to 12 miles from shore.

Spawning occurs at night from January to September, with peak activity occurring between April and August. In the southern Gulf of Mexico, spawning occurs over a longer period and may even happen year-round.

Spawned eggs hatch within 24 hours. The larval stage lasts one to three days, and most larval development takes place in nearshore and inshore waters. During the post-larval stage, the yolk sac is absorbed, and new bone is laid down in the head region. Transformation to juvenile fish occurs 25 days after hatching.

Adult scaled sardines feed exclusively on plankton, straining prey items from the water with their gillrakers. Key predators of scaled sardines are seabirds, king and Spanish mackerels, little tunny, gag, bluefish, crevalle jack, yellowfin and bluefin tuna, and dolphin. Yes, I know snook like them too.

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Atlantic thread herring (Opisthonema oglinum) have a lot of nicknames — threadfin, threadies, greenies, greenbacks and shiners. These nearshore pelagic fish form dense surface schools. Their common name refers to the long ray that trails from the back of their single dorsal fin like a piece of thread. Threadfin make good bait, but they are delicate and do not tolerate overcrowding in baitwells.

Threadfin feed on plankton, but occasionally consume small fish and crustaceans. Estimated to live up to 8 years, females reach maturity around 5.5 inches fork length (FL) and males at 5 inches FL, and at one to two years in age.

Adult threadfin generally follow a seasonal north-south and inshore-offshore migration pattern along the west coast of Florida. Schools of fish move south in the fall and concentrate in the winter within 10 miles of shore.

Threadfin spawn over a wide area in the Gulf of Mexico and South Atlantic. Spawning can occur from February to September, but peak spawning is from April to August. Most spawning takes place within 30 miles of shore at depths less than 100 feet. The primary spawning area for threadfin is located in coastal waters from Tampa Bay to just south of Fort Myers. Spawning generally occurs when water temperatures exceed 78°F and when salinity is above 35 parts per thousand (full-strength seawater).

Eggs and larvae are generally found over the inner continental shelf off the west coast of Florida. Juveniles occur in the same areas as adults and are found in estuarine waters during the summer months. Adults and juveniles form schools near the surface and generally remain in schools throughout their life. The size of the schools increases in the fall prior to migration offshore.

King and Spanish mackerel, bluefish, and crevalle jack have all shown a preference for eating schooling fish such as threadfin. One study found that 59 percent of the food eaten by king mackerel in Florida waters consisted of threadfin and scaled sardine. Threadfin are also preyed upon by sea birds, wading birds, and bottlenose dolphin.

Betty Staugler is the UF/IFAS Extension Charlotte County agent for the Florida Sea Grant Program. She is active in many areas relating to boating, fishing, and watershed/coastal living. Sea Grant supports research and education activities that help Florida’s shoreline communities, industries and citizens wisely use the state’s coastal and marine resources. Contact her at staugler@ufl.edu or 941-764-4346.

Betty Staugler is the UF/IFAS Extension Charlotte County agent for the Florida Sea Grant Program. She is active in many areas relating to boating, fishing, and watershed/coastal living. Sea Grant supports research and education activities that help Florida’s shoreline communities, industries and citizens wisely use the state’s coastal and marine resources. Contact her at staugler@ufl.edu or 941-764-4346.

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