Will it live? Release survival for panfish, deep fish and live-bait catches

"Catch and release" sounds like the fish is fine, and most of the time it is. But the research is clear that some released fish die, and that the number depends heavily on how and where the fish was caught. This guide goes past "get it out quick" and looks at what the studies measured, mostly for the fish Texas anglers catch most: panfish, fish pulled up from deep water, and fish that took live bait. It adds to the handling guide, which covers the hands-on steps from TPWD.

How many released fish die?

A 2005 review by two fisheries scientists (Bartholomew and Bohnsack) pulled together 53 release-mortality studies, which was more than doubling the estimates in an earlier review. Across 274 estimates, the median was 11 percent, the mean was 18 percent and the range was 0 to 95 percent. About 46 percent of the estimates were under 10 percent, and about 22 percent were over 30 percent. The authors note that mortality varied greatly by species and even within a species, and that the distributions were similar for salmon and trout, marine fish and freshwater fish.

So "released fish usually live" and "released fish sometimes die" are both true. The useful question is what moves a catch toward the low end or the high end.

What moves the number

The same review found that where the hook ended up was the most important factor: fish hooked in critical areas such as the gills or gut died more often. It also found these were significant:

The review did not find an overall effect, across all the estimates, for fish size, hook size or whether the hook was a treble or a single. Venting (letting gas out of a swollen fish) is covered below.

Panfish: crappie and bluegill

Two older studies are worth knowing. In a Mississippi study of white crappie (Hubbard and Miranda, 1989), fish caught by hook and line in shallow water and released had an average mortality of 3 percent measured 6 to 11 days later, and there was no significant difference between live and artificial baits. Size made no significant difference either. Depth did: when fish were rapidly depressurized in a simulated deep-water catch, none died at depths of 10 meters (about 33 feet) or less, but 29 percent died after coming up from 13 meters (about 43 feet) and 67 percent after coming up from 16 meters (about 52 feet), measured over 96 hours. The authors concluded that release rules may work less well where fish are often caught from deep water. The feet figures are our conversions.

In an Illinois study of bluegills (Hoxmeier and Wahl, 2009) at Ridge Lake, fish released right away had 4.4 percent initial and short-term mortality. Fish caught on live bait died at 6.6 percent and fish caught on artificial baits at 0 percent. Larger fish were less likely to die after release. The big difference was holding: bluegills kept in wire fish baskets died at 34.0 percent compared with 7.6 percent in live wells, and in live wells the 3-hour and 5-hour holds were worse than a 1-hour hold. The authors concluded that catch and release causes some mortality but does not appear to seriously harm bluegill populations. These are two lakes in specific years, not a promise for every Texas lake.

If you are going to keep fish on a stringer or in a basket while you fish, the bluegill study is the one to remember: how you hold a fish before release can matter more than how you caught it. If you do not plan to eat it, let it go right away.

Deep-water and suspended fish

Fish brought up from deep water can suffer barotrauma, because the gas in the swim bladder expands as the pressure drops. For black basses, TPWD advises avoiding catch and release in water deeper than 30 feet, and says release is stressful above 70°F and very stressful above 80°F. The crappie study above points the same way: the deeper the fish came from, the worse it did. The most reliable way to improve the odds is to not make a release depend on a long trip up from deep, warm water: fish shallower, fish the cool part of the day, or, where the rules allow, plan to keep the fish you catch from deep water.

On venting, the evidence is mixed. In the 2005 review, four studies found venting reduced mortality and two found no effect, and the combined data showed no significant overall effect, though venting did significantly reduce mortality for four species. The authors say more research is needed. TPWD's guidance on swollen fish is in the handling guide; use it, and treat any venting as something to learn properly first, not as a fix for a deep catch.

Live bait: the bait that gets swallowed

Live bait is not the problem by itself. The problem is that fish tend to swallow it, and a deeply hooked fish is the one most likely to die. The studies above are mixed on whether bait type mattered for the fish they tested (not for white crappie, yes for bluegill), so treat live bait as a risk to manage, not a rule:

Fish you did not mean to catch

Bycatch is the fish that took your bait but is not the one you wanted: an undersized fish, a species you cannot keep, a gar or a catfish on a bass lure. The studies above do not treat an unwanted fish differently from a wanted one, so give it the same care: leave it in the water if you can, wet your hands, keep it out of the water no longer than you can hold your breath (TPWD's rule of thumb), and cut the line if it is hooked deep.

A short checklist

This is a summary of the studies and of TPWD's pages, not legal advice. Check TPWD's Outdoor Annual for the rules on tools, length and bag limits before you fish. Mortality numbers come from specific species, waters and years and may not match what you catch.

For more reading, we suggest these articles

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