Population-Estimation

The direct-proportion method was used to estimate fish populations in Areas 1, 3 and 6. Reliable results could not be obtained for all species because of scarcity, mortality in handling, mobility, or other factors.

A high rate of mortality due to handling was observed in Area 1 for the red shiner and in Area 6 for river carpsucker (young-of-the-year), sucker-mouthed minnows, red-finned shiner, red shiner, blunt-nosed minnow, and stoneroller. In Area 3, in contrast, there was little mortality in the same species during the twelve-hour interval that fish were held in traps prior to release as marked individuals.

The following species were common in at least one area, but probably are sufficiently mobile (see page 416) to invalidate estimates of static populations in small areas: red shiner, red-finned shiner, and channel catfish (yearlings and older). Other species were rare and are indicated as "T" in Table 13.

Those species for which population-estimates seem warranted include: golden redhorse, sucker-mouthed minnow, red shiner, sand shiner, fat-headed minnow, stoneroller, stonecat, channel catfish (young-of-the-year), green sunfish, long-eared sunfish, slender-headed darter, and orange-throated darter. I consider the estimate valid if a high percentage of the marked fish is recaptured. Results are presented in Table 15, and ordinarily will not be referred to in the following discussion of the population in each of the three areas.

Area 1

The order of abundance at Area 1, in terms of the estimated population per 500 square feet, was as follows: stoneroller (47.6), stonecat (29.4), channel catfish (young-of-the-year) (20.6), green sunfish (19.4), red shiner (18.2), long-eared sunfish (9.4), channel catfish (yearlings and older) (6.5), golden redhorse (1.2). Insufficient data make inclusion of other species unreliable.

A comparison of the order of abundance between the estimated total population and the percentage composition in the first collection from each area shows significant correlations. The percentage-composition of the fish fauna at Area 1 was calculated as follows: stoneroller (27.7%), red shiner (18.2%), green sunfish (11.2%), stonecat (10.3%), channel catfish (young-of-the-year) (9.5%), channel catfish (yearlings and older) (5.8%), long-eared sunfish (5.4%), golden redhorse (0.8%). It can be seen that the stoneroller, green sunfish, long-eared sunfish and golden redhorse follow each other in the same order in both calculations. The stonecat is shown to be more common than channel catfish (young-of-the-year) in both calculations, but both species appear to be more abundant than green sunfish and red shiner in calculations of the total population and less abundant in the percentage-composition in the first collection. I think that the order of abundance as shown by percentage-composition is the more accurate figure for Area 1. The abundance of the red shiner is known to have been affected by mortality in collecting. Furthermore, as will be shown later, the species is so mobile that its abundance often changes markedly in a short time. Therefore, it is not surprising to find the red shiner in widely varying positions of relative and absolute abundance. However, the green sunfish maintains stable populations and should remain in about the same position of abundance in relation to other species (such as the stonecat and channel catfish young-of-the-year) that also maintain stable populations. The differences in order of abundance obtained by the two methods for green sunfish and channel catfish young-of-the-year are not great. However, in the estimation of total population the abundance of the stonecat seems significantly greater, in relation to other species, than in the calculation of percentage-composition. I believe that this difference can be attributed to the relatively low number of marked fish recaptured, which is probably due to a slow rate of dispersal from the point of release. Stonecats were released in relatively quiet water, and if they remained there they might be missed in subsequent collections, because they lack air-bladders and tend to remain on the bottom when shocked. Therefore, the calculated total population of the stonecat in Area 1 may be too high.

Table 15. Data Used in Estimating Total Populations, by Direct Proportions, in Areas 1, 3, and 6 at the Upper Neosho Stations.

Species	Number captured first collection			Number marked and released			Number captured second collection			Number of marked fish recaptured			Estimated total population			Percent of marked fish recovered			Number per 500 square feet
Species	1	3	6	1	3	6	1	3	6	1	3	6	1	3	6	1	3	6	1	3	6
Golden Redhorse	2	5	0	2	5	0	2	5	0	2	5	0	2	5	0	100	100	—	1.2	.4	0
Sucker-mouthed Minnow	0	54	31	0	51	15	0	42	12	0	17	0	0	126	—	—	33	0	0	10.0	—
Red Shiner	44	116	186	22	106	86	7	165	202	5	18	14	31	972	1284	23	17	11	18.2	77.1	64
Sand Shiner	0	25	10	0	25	7	0	35	10	—	12	1	0	73	—	—	48	—	0	5.8	—
Blunt-nosed Minnow	0	4	108	0	3	28	0	10	91	0	1	8	0	—	319	—	33	28	0	—	16
Fat-headed Minnow	1	1	112	1	1	101	0	2	156	0	0	19	—	—	830	0	0	19	—	—	41.5
Stoneroller	67	84	54	58	79	33	39	107	67	28	35	8	81	242	276	48	44	24	47.6	19.2	13.8
Channel Catfish (j)[I]	14	37	3	9	32	3	7	16	1	6	13	0	11	39	—	67	41	0	6.5	3.1	—
Channel Catfish (yy)[J]	3	34	40	22	33	39	16	34	23	10	11	1	35	102	—	45	33	3	20.6	8.1	—
Stonecat	25	7	0	25	7	0	8	7	0	4	1	—	50	—	0	16	14	—	29.4	—	0
Green Sunfish	27	[K]—	62	27	—	62	17	—	62	14	—	22	33	—	175	52	—	35	19.4	—	8.8
Long-eared Sunfish	13	6	10	13	6	10	12	3	22	10	3	6	16	6	37	76	50	60	9.4	.5	1.9

Area 3

The order of abundance of the species at Area 3, in terms of the estimated population per 500 square feet, was as follows: red shiner (77.1), stoneroller (19.2), sucker-mouthed minnow (10.0), channel catfish (young-of-the-year) (8.1), sand shiner (5.8), channel catfish (yearlings and older) (3.1), long-eared sunfish (0.5), golden redhorse (0.4). Insufficient data make inclusion of other species unreliable.

For comparison with the estimates of total population, the percentage-composition in the first collection gives the following results: red shiner (24.0%), stoneroller (17.4%), sucker-mouthed minnow (11.2%), channel catfish (yearlings and older) (7.6%), channel catfish (young-of-the-year) (7.0%), long-eared sunfish (6.0%), sand shiner (5.2%), and golden redhorse (1.0%).

For the most part, the species have the same order of abundance in both methods of analysis. Those that are apparently out of order are channel catfish (yearlings and older) and long-eared sunfish. The first species is mobile (excepting young-of-the-year) and commonly fluctuates widely in numbers in the same area; the second species was treated differently in that only adults were considered in the population-estimation whereas both young and adults were considered in calculating percentage-composition. (I found that I could not confidently distinguish between young-of-the-year of green sunfish, long-eared sunfish and orange-spotted sunfish after staining.)

Area 6

The order of abundance of the species at Area 6, in terms of the estimated population per 500 square feet, was as follows: red shiner (64.0), fat-headed minnow (41.5), blunt-nosed minnow (16.0), stoneroller (13.8), green sunfish (8.8), long-eared sunfish (1.9). Insufficient data make inclusion of other species unreliable.

Calculations of percentage-composition give the following results: red shiner (20.1%), long-eared sunfish (14.6%), green sunfish (12.2%), fat-headed minnow (12.1%), blunt-nosed minnow (11.7%), stoneroller (5.8%). The two species of sunfish form a more significant part of the population in the latter analysis because young are included. Only adults were considered in the estimation of total population.

The fact that estimates of the total population and the percentage-composition agree in most respects lends support to the validity of both methods of analysis. It should be re-emphasized that differences in the order of abundance in the various areas reflect the ability of each species to utilize each particular kind of habitat.