Habitat and growth in Mississippi
Last month, I discussed the importance of food supply and temperature to one of Mississippi’s more-popular sportfish — the catfish.
In a rigorous analysis of a nationwide data set that included 46 blue catfish populations, 125 channel catfish populations and 44 flathead catfish populations, fisheries scientist Andrew Rypel found that blue catfish, as expected, grew faster in warmer climates. But Rypel’s analysis also found the growth of channel catfish and flathead catfish was not significantly related to temperature.
All catfish — blues, channels and flatheads — are warm-water fish that begin active feeding and rapid growth when water temperatures climb above 70 degrees Fahrenheit. Thus, while faster growth of blue catfish in Southern climates than in northern climates was expected, the failure to find faster growth of channel catfish and flathead catfish in the South was surprising.
Rypel suggested that food supply and the density of fish sharing the forage might have overshadowed the effect of temperature. This is likely because food supply commonly limits the growth of all fishes.
Unfortunately, data was not available to include food supply in the statistical analyses that tested factors affecting catfish growth.
Habitat also can affect growth. How catfish growth is affected by habitat is an interesting question because all three catfish do well in standing water (lakes, reservoirs and ponds) or flowing water (rivers and streams).
But where do they grow faster?
Blue catfish are considered the denizen of big rivers, and many biological reference books describe their primary habitat as main channels of large rivers. Yet, blue catfish thrive and grow to enormous proportions in reservoirs.
The name channel catfish suggests a fish that occupies the channels of rivers and streams. Yes, channel catfish are common in rivers, but the adults congregate in the deeper, slower-flowing pools and avoid fast flows.
The large numbers of channel catfish caught in ponds and impoundments, the Mississippi state-record channel catfish caught from Lake Tom Bailey and the millions of pounds of channel cats reared in aquaculture ponds every year are testimony that channel catfish grow well in ponds.
Flathead catfish are native to rivers and streams. But flatheads are now common in many reservoirs, and the world-record flathead catfish was caught from a reservoir. Clearly, this fish-eating machine grows well in standing and flowing habitats.
Rypel used his nationwide database to test whether blue, channel and flathead catfish grow faster in standing water or flowing water.
Analysis indicates blue catfish grew faster in flowing water systems, channel catfish grew faster in standing water systems and growth of flathead catfish did not differ between standing and flowing water.
Putting this all together:
• Blue catfish tend to grow faster in Southern rivers.
• Channel catfish tend to grow faster in ponds, whether in the North or in the South.
• Flathead catfish have fast growth in any water body — lake or river, North or South — where they have abundant and available forage fish.
Catfish are long-lived fish, and trophy catfish — even those with very fast growth — are usually 15 years old or older. As a postscript to Rypel’s analysis, his generalizations pertain to catfish up to 10 years old and do not necessarily provide suggestions for the best places to look for trophy catfish.
Now that I’ve discussed where catfish tend to grow fastest using a nationwide database, what do we know about catfish growth in Mississippi waters? Unfortunately, catfish have largely flown under the fisheries biologists’ radar in this state, and few rigorous growth studies have been conducted.
The most-comprehensive assessment of blue and flathead catfish growth was for Mississippi River populations. Channel catfish are relatively scarce in the Mississippi River but are abundant in Mississippi’s smaller rivers. Of the rivers where channel catfish growth has been monitored, the fastest growth was found in the Sunflower River.
Certainly some populations will have faster growth and others will have slower growth, but the following table gives some idea about how fast catfish grow in Mississippi. The table provides benchmarks for how large catfish grow after age 3, 6 and 9 years of age in Mississippi. For contrast, I’ve included the maximum reported length of 9-year-old catfish from any water in the United States.
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