Wiper

What a wiper is

A wiper is not a species. It is a hatchery cross between striped bass and white bass, produced by stripping eggs and milt from the two parents, fertilising in a bowl and incubating the result — there is no wild population and no natural origin. Every wiper in a Plains reservoir was made in a hatchery and released.

The cross has a direction, and the direction has a name. The original cross, made in South Carolina in 1965, used eggs from a female striped bass fertilised with sperm from a male white bass, and is called the palmetto bass. The reciprocal — a female white bass crossed with a male striped bass — was first produced in Florida in 1973 and is called the sunshine bass. South Carolina’s own account confirms the original as a striped bass female and a white bass male, developed at the Dennis Wildlife Center in the mid-1960s, and North Carolina State’s history of the industry credits Bob Stevens with the 1965 female striped bass × male white bass palmetto cross.

Where the name “wiper” attaches to a specific cross, it usually means the palmetto. Kansas is explicit that the fish it stocks is the palmetto variety, made using the striped bass egg and white bass sperm. Iowa defines its hybrid striped bass the same way, a cross between a female striped bass and a male white bass.

The convention is reported backwards often enough to be worth flagging. Nevada’s wildlife agency, for instance, defines a wiper as crossing a female white bass with a male striped bass — which is the sunshine cross under the standard naming. Both usages exist in official state material. The honest summary is that “wiper” is a regional common name for hybrid striped bass generally, most reliably documented as the palmetto cross in the Plains states, and that unless a hatchery record says which parent supplied the eggs, the cross direction of any given stocked fish cannot be assumed. Once past the larval stage the two crosses are, in any case, physically indistinguishable.

Why Plains states stock them

Reservoirs on the Missouri, Kansas, Republican, Platte and Arkansas systems share a common problem: enormous standing crops of gizzard shad that outgrow the mouths of most native predators. Adult gizzard shad become too deep-bodied for largemouth bass and walleye to handle, so the shad population expands unchecked, competes with young sport fish for zooplankton, and converts reservoir productivity into biomass nothing can eat.

Hybrid striped bass are the standard tool against that. They are open-water schooling predators with a large gape and a fast growth rate, and they will chase adult shad in the pelagic zone where largemouth will not go. Iowa states the rationale directly: hybrids went into Saylorville Reservoir starting in 1981 to control gizzard shad and to give anglers an additional sport fish. Nebraska has used them for a related job, in reservoirs restructured by introduced white perch — a species the USGS records as having taken one Nebraska reservoir from 74% black bullhead to 70% white perch within three years.

The second reason is practical. Striped bass fingerlings are fragile. South Carolina developed the cross in the first place because hybrids showed markedly reduced sensitivity to the stress of transport and stocking at small sizes compared with pure striped bass. A hatchery can move more hybrids, further, with better survival, for the same money.

The third is that hybrids hold up in water that striped bass do not. Plains reservoirs are shallow, turbid, warm in summer and prone to severe drawdown. Striped bass need cool, well-oxygenated water and are squeezed hard in August; hybrids carry enough of the white bass tolerance to persist. Nebraska notes that it has not stocked striped bass since the early 1980s while maintaining wiper fisheries by regular stocking in selected reservoirs statewide.

The programmes

Kansas runs one of the larger operations. Rather than trading for fish from other states — unreliable in supply and a route for accidentally importing unwanted species — the Milford hatchery began domestic production in 1993, with the first domestic striped bass spawning in a Kansas hatchery in 1997. Broodstock are grown out in raceways to breeding age at around four years, and fry reach one to three inches in about thirty days.

Colorado stocked wipers into eastern-plains reservoirs beginning in the early 1980s and reports growth to roughly seven pounds in three years, with fish exceeding twenty pounds by about age ten where forage allows. Iowa’s Saylorville programme has produced fish over twenty pounds; the state record is 19 lb 10 oz from Saylorville in August 2005, though Iowa also notes hybrids elsewhere seldom exceed ten pounds. Kansas gives a state record of 22 pounds.

None of these fisheries are self-sustaining. They are maintenance stockings, repeated on a schedule, and when stocking stops the fishery ages out and disappears within a few years.

Fertile, not sterile

Hybrid striped bass are frequently described as sterile. That is not accurate, and it matters for the reason agencies stock them. The University of Florida’s extension publication states that hybrid striped bass are not always sterile like most other hybridised fish, and that there have been reports of natural spawning in reservoirs stocked only with hybrids. Texas A&M’s programme puts it more flatly: the hybrids are fertile and reach sexual maturity at two years. Nevada, by contrast, describes wipers as predominantly stocked as a sterile hybrid. The sources conflict.

The more defensible framing is near-sterility in practice. Hybrids can produce gametes and have been spawned in the laboratory; South Carolina notes hybrids exhibit striped-bass-like spawning behaviour but that natural reproductive success remains questionable. Practically, a hybrid attempting to spawn in a Plains reservoir faces the same barrier its striped bass parent does: semi-buoyant eggs that require a long stretch of continuously flowing river to stay suspended, in systems where that habitat does not exist. Reduced fertility plus absent spawning habitat is why agencies can stock a large predator every year without establishing a permanent, unmanageable population. Backcrossing with white bass is a documented concern in some systems, and it is one reason states track hybrid stockings rather than treating them as inert.

Water temperature

Wipers sit thermally between their parents, closer to the white bass end. The most useful compiled numbers come from a thermal tolerance review prepared for Nevada’s water-quality criteria, which found optimum growth between 21°C and 26.8°C (70–80°F) depending on how much food is available — 21°C on a restricted ration, 26.8°C on a full one — with growth still at 80% of optimum at 32°C (90°F) when fish are feeding heavily. That ration dependence is worth holding onto: in a reservoir with a heavy shad crop, wipers do well noticeably warmer than in one without.

Field behaviour is tighter than the laboratory numbers suggest. Radio-tracked hybrids in an Illinois lake avoided water at 27°C (81°F) and above. Nevada’s derived criteria are a chronic weekly average of 30°C (86°F) and an acute maximum of 31°C (88°F), the latter borrowed from the parent species because no published acute tolerance study for wipers could be found. At the cold end, feeding slows sharply: aquaculture practice is to suspend feeding below 60°F (15.6°C), and feed conversion collapses above 90°F (32.2°C).

Set against a striped bass avoidance threshold of about 26.4°C (79.5°F), the hybrid’s few degrees of extra tolerance is the whole reason it works in shallow Plains impoundments where a striped bass programme would fail.

Rivers, tailwaters and behaviour

Wipers are open-water fish that use current the way white bass do. Iowa describes them holding in deep water near baitfish, along creek channels, in flooded timber, and around dams and current seams, including in river reaches and Mississippi River pools rather than only in reservoirs. Because stocked fish move, wiper fisheries frequently develop below the reservoirs they were stocked into: tailwaters concentrate shad, hold cooler and better-oxygenated water in summer, and give the fish exactly the boundary they hunt against.

The surface-feeding behaviour Colorado calls “busting” — schools driving shad up and attacking from below — is inherited from both parents and is most visible in the warm months, when Iowa notes hybrids feed hardest at sunrise and sunset as bait disperses through the water column. That schooling habit, more than size, is what makes the fish conspicuous.

Identification

Wipers look like a heavy-shouldered white bass. Colorado describes a dark gray to silvery-blue body with six to eight thick, broken horizontal stripes, contrasting with the unbroken stripes of a striped bass. The body is slightly arched, between the pronounced arch of a white bass and the straight profile of a striper. Kansas gives the definitive character: like its striped bass parent, the wiper has two rows of teeth near the rear of the tongue, where a white bass has one patch. On hybrids the two patches are usually crowded close together rather than cleanly separated.