Comparative distribution and abundance of catfishes (Ictaluridae and Ariidae) in an oligohaline upper estuary.

ABSTRACT--Eight species of catfishes were collected during a survey of Lake Maurepas, an oligohaline part of the upper Lake Pontchartrain estuary. Sampling methods included otter trawl, gill net, and rotenone. Juvenile and adult blue catfish, Ictalurus furcatus (Lesueur), and juvenile channel catfish, Ictalurus punctatus (Rafinesque), far outnumbered other species. Adult Ictalurus furcatus were present in consistent numbers throughout the lake and during all sampling periods in 1983-84, but were greatly reduced in numbers in 2000 during a period of higher than normal salinities. Juveniles of both species were present in largest numbers in winter and spring. Juvenile I. furcatus were mostly caught at stations around the perimeter of the lake and away from the source of estuarine waters, whereas juvenile I. punctatus were more randomly distributed about the lake.

Key words: catfishes, Lake Maurepas, Ictaluridae, Ariidae, Louisiana.

INTRODUCTION

Upper estuaries are unique habitat types where freshwater tributary environments merge into saline environments of the estuary. Such habitats support mixed assemblages of aquatic organisms, including both marine and freshwater species. Lake Maurepas, at the upper end of the Lake Pontchartrain estuary in Louisiana, is an oligohaline, cypress-lined lake approximately 15 km across (Fig. 1). The open lake is 3-4 m deep with open mud bottom. The shoreline is eroding as a result of sea level rise and land subsidence, resulting in numerous submerged logs and stumps along the shore.

[FIGURE 1 OMITTED]

There is some evidence that average salinity had increased slightly in the early 1980s, although there is considerable annual variation and maximum levels are usually quite low (0-2.5 ppt in 1983-1984 in Lake Maurepas, Table 1A; 0.02-8.00 ppt in Pass Manchac: Sikora and Kjerfve 1985). Salinities in Lake Maurepas increased dramatically in 1999-2000 when southeastern Louisiana experienced a significant drought. Annual rainfall amounts at New Orleans were 117 cm (46 inches) in 1999 and 99 cm (39 inches) in 2000, some 35-53 cm (14-21 inches) below the normal 152 cm (60 inches) (National Weather Service Data, www.srh.noaa.gov). This reduced level of rainfall and freshwater input to the upper Lake Pontchartrain estuary resulted in dramatic salinity increases. Salinities in Lake Maurepas in 2000 were considerably higher during most of the year, 5.0-7.1 ppt during August-October. Turbidity levels were greatly reduced in 2000 (Table 1C), partly correlated with the increased salinity, but also largely resulting from the ban on shell dredging imposed in Lake Maurepas in 1983, and in Lake Pontchartrain in 1990.

Anecdotal reports indicated that large numbers of usually uncommon marine species had entered Lake Maurepas, as well as Lake Pontchartrain, in 1999-2000. Access between the lake and the lower estuary, as well as influx of saline waters, is possible only through narrow passes on the northeast side of the lake. Fishing boats were often gathered at the Pass Manchac entrance into Lake Maurepas to fish for sand and spotted sea trout (Cynoscion arenarius and C. nebulosus). Freshwater inflow occurs primarily from three rivers on the north and west sides of the lake. The fish fauna is a mixture of marine and freshwater species, including about 55% freshwater species, 40% marine or estuarine species, and 4% diadromous species (Hastings et al. 1987). Catfishes are a major part of the fish fauna and support a significant commercial fishery. The major goal of this study was to determine the distribution and abundance patterns of catfishes in the lake, and their correlation with season and environmental variables, such as the effects of the increased salinity in 2000.

METHODS

Most of the historic data presented here were taken from a survey of the lake conducted during 1983-1984 (Hastings et al. 1987, Childers et al. 1985). Sampling was conducted at seven stations approximately bimonthly (September, November, January, April, June, and September, designated as sampling Periods 1-6). Sampling dates are given in Table 1. Stations were identified and relocated by a LORAN C APL-900 electronic navigator so that sampling was always conducted in the same 3.4-sq. km. (one sq. nautical mile) area. Stations 1-4 were located around the western perimeter of the lake near the major sources of freshwater input. Station 5 was located on the northeast side near Pass Manchac and the source of saline waters. Stations 6 and 7 were mid-lake stations.

Sampling methods included otter trawl, multimesh multifilament nylon gill nets, and large mesh multifilament nylon gill nets at all stations and periods, and shoreline rotenone at Stations 1-5 (perimeter lake stations) during May (twice), July-August, and September 1984. Gill net effort at each station included four multimesh nets 45.7 m long and 2.4 m deep composed of six 7.6 m sections of 8.9, 7.6, 6.3, 5.1, 3.8, and 2.5 cm bar mesh, and two large mesh nets 61 m long and 2.4 m deep with 11.4 cm mesh. Gill nets were set to fish for approximately 12 h. Catch per unit effort (CPUE) for gill nets was calculated as the number of fish caught per hour of net set.

Standard otter trawl sampling involved three 10-min tows with a 4.9 m trawl with 1.9 cm bar mesh and a 0.6 cm mesh cod end for the capture of small specimens. Usually one trawl tow was taken in late evening and two were taken in early to mid-morning of the following day. CPUE for trawls was calculated as the number of fish caught per 10 min of trawling time.

Rotenone was used to sample shorelines at Stations 1-5. A 0.5 ha shoreline area measuring approximately 29 m x 3 m was enclosed with a block net (0.64 cm mesh) and treated with 5% liquid rotenone to produce a 1-3 ppm concentration. Condition (K) of catfishes was determined by the formula:

K = W [10.sup.5]/[L.sup.3]

where W=weight in grams and L=total length in mm.

Environmental conditions were recorded at the time of each net set, and included temperature, salinity, conductivity, secchi disk reading, dissolved oxygen, wind speed and direction, and cloud cover.

The seven stations sampled in 1983-1984 were also sampled twice by trawl in 2000, in August and again in September-October. Their locations were determined with GPS units. The trawling methods used were identical to those used in 1983-84, except that the three tows taken at each station were all taken on the same day.

RESULTS

Eight species of catfishes (4,796 individuals) were collected in 1983-1984 (Table 2), including six freshwater species (Ictaluridae) and two marine species (Ariidae). Blue catfish (Ictalurus furcatus) and channel catfish (L punctatus) were by far the dominant species, and were collected in substantial numbers in every sampling period during 1983-84 (Table 3). Three species (black bullhead, Ameiurus melas, tadpole madtom, Noturus gyrinus, and sea catfish, Arius felis) were represented by single individuals. Three species (flathead catfish, Pylodictus olivaria, yellow bullhead, Ameiurus natalia, and tadpole madtom) were collected only with rotenone, suggesting an association with the sheltered shoreline habitats of cypress stumps and roots. The black bullhead and sea catfish were collected only by gill net. The two marine species (sea catfish and gafftopsail catfish, Bagre marinus) were present only during the last sampling period in 1983-1984, when salinity had reached its highest level (0.2-1.4 ppt; Table 1A). However, neither species was collected in our samples during 2000, although local commercial fishermen reported increased catches of gafftopsail catfish on their trotlines in the lake during 2000. Their absence from our collections suggests that they were not especially common in the lake.

Only three species were collected in 2000. The two dominant species of freshwater catfish (blue catfish and channel catfish) were present but much less numerous in 2000. A single flathead catfish was collected at Station 1 in October.

The two dominant ictalurids were present in substantial numbers throughout the year in 1983-1984, but with higher catches during the fall, winter, and spring (November, January, and April). Over 99% of the total catch for both species resulted from trawl and multi-mesh gill net sampling. Consequently, subsequent discussion of the catch data will be based upon these two sampling methods. Two major size classes were present in the catches for both trawl and gill net, with modal sizes (total length) approximately 50-150 mm and 250-400 mm for blue catfish (Fig. 2) and 50-150 mm and 200-300 mm for channel catfish (Fig. 3). Juvenile blue catfish were more numerous during January and April, while adults were about equally common during all sampling periods. Juvenile channel catfish were abundant during November, January, and April, whereas the number of adults was always quite low. In August 2000, only the larger size class of blue catfish (modal size 160-300 mm), corresponding to the larger class of 1983-1984, was present. No blue catfish were collected in September-October 2000. Channel catfishes were rare in both August and September-October of 2000. Those collected ranged in size from 148 to 213 mm.

[FIGURES 2-3 OMITTED]

Catch per gill net hour (CPUE) for adult blue catfish was similar for all periods and stations (Table 3, Fig. 2), except during November 1983, and September 1984, primarily because of larger catches at Station 5. Trawl CPUE suggests that juveniles of this species were usually more numerous at perimeter lake stations on the west (freshwater) side of the lake. Catches of juveniles during September 1983, June 1984, and September 1984, were lower than during other periods (Trawl catches for several stations in September 1983, were high because of relatively larger numbers of adults collected at Stations 1-4). Trawl CPUE for both species was reduced in 2000, especially during September-October.

Gill net CPUE for channel catfish was quite variable among stations and periods, and was about one tenth that of blue catfish (Table 4, Fig. 3). Juvenile channel catfish were abundant (and more numerous than juvenile blue catfish) during November, January, and April, especially at Station 4.

DISCUSSION

The catfish fauna of Lake Maurepas is dominated by two freshwater species, the blue and channel catfish, which are usually abundant in the open waters of the lake. Sheltered shoreline habitats support other species in lesser numbers, and periods of increased salinity may induce marine species to move into the lake. Freshwater tributaries entering the lake (Blind River--Watson et al. 1981, Amite River--Laiche 1980, and Tickfaw River-Saul 1974) also support larger numbers of yellow bullhead, tadpole madtom, and flathead catfish. Several other species are restricted to shallow, upstream tributaries: black madtom (Noturus funebris), speckled madtom (N. leptacanthus), brindled madtom (N. miurus), and freckled madtom (N. nocturnus). Of the two dominant species, the blue catfish is most characteristic of the lake. Adults of this species are present in consistent numbers throughout the lake and throughout the year. However, there appeared to be some correlation between the distribution of juveniles of this species and salinity in 1983-1984. Salinity ranged from 0-2.5 ppt during 1983-1984, with levels near zero during the first four sampling periods and 1-2 ppt during the summer and fall of 1984 (Table 1A), with higher values on the northeast side and during the last two sampling periods. The channel catfish, in contrast, was represented primarily by juveniles. Catch patterns were not consistent but did seem to suggest decreased abundance at stations with higher salinities. The drastic increase in salinity in 2000 resulted in a major reduction in the abundance of both species of catfishes in the lake. Since no fish kills were reported on the lake during this period, catfish may have moved up into the tributary rivers to escape the saline waters.

Three non-catfish species, all of which are marine (silver perch, Bairdiella Chrysoura; spotted seatrout, Cynoscion nebulosus, and striped anchovy, Anchoa hepsetus) were collected in 2000 in very small numbers, but not in 1983-1984. Bay anchovy (Anchoa mitchilli) and Atlantic croaker (Micropogonias undulatus) remained the dominant species, but the latter was much less numerous in 2000 than in 1983-1984. Surprisingly, other marine species common in 1983-1984 were also reduced in abundance (gulf menhaden, Brevoortia patronus, and sand seatrout, Cynoscion arenarius) or not collected at all in 2000 (spot, Leiostomus xanthurus, and hogchoker, Trinectes maculatus). Freshwater drum (Aplodinotus grunniens) were also much less numerous in 2000. The higher salinity may have been sufficient to reduce the abundance of freshwater species in the lake, but not high enough to greatly influence the abundance of marine species. Other, undetermined factors may have been more significant in affecting the distribution of many species.

The preponderance of blue catfish (and lack of large channel catfish) in the lake does not appear to be a recent development although the lack of larger channel catfish could be associated with over-fishing (Tim Morrison, pers. comm.). Heavy commercial fishing pressure may have selectively reduced the channel catfish population. On the other hand, Davis et al. (1970) collected three times as many blue catfish as channel catfish in otter trawls in Maurepas and Turner and Savoie (1976) collected 373 blue catfish and no channel catfish in Lakes Pontchartrain and Maurepas. Thompson and Verret (1980) collected four times as many blue catfish as channel catfish in Lake Pontchartrain, although channel catfish were more numerous in marsh canals surrounding the lake. Other lakes in the area, such as Lac des Allemands and Lake Salvador are dominated by channel catfish, whereas blue catfish are much less common (Perry and Williams 1986).

Thompson and Verret (1980) demonstrated the same seasonal pattern, with higher catches in the winter and spring (December to May). They also demonstrated a seasonal pattern for sea catfish and gafftopsail catfish, which were present only from April through November. In addition, the sea catfish was never collected at salinities less than 0.7 ppt.

Occasional catfish in the area are quite thin and emaciated. However, condition factor determinations (Table 5) suggest that populations of both species fall within normal ranges for freshwater habitats (Carlander 1969).

Estuaries such as the Lake Pontchartrain system are inherently unstable, with much variation in environmental conditions, including salinity. Most fish species occurring in estuaries are well adapted to tolerate such variation, but some may be redistributed by significant changes in salinity. This seems to have occurred in Lake Maurepas, although the general composition of the fish fauna, as reflected by the dominant species, remained the same. Although some marine species may have entered the lake as a result of the increased salinity, there was not a major influx of marine species.

TABLE 1. Water quality data for Lake Maurepas.

     Period/Date           St. 1          St. 2          St. 3

    A. Salinity/Conductivity data (in parts per thousand and
                      microsiemens per cm)

1) 19 Sep-6 Oct 1983     0   (0.12)       0 (0.14)       0 (0.14)
2) 31 Oct-16 Nov 1983    0.1 (0.14)       0 (0.17)       0 (0.15)
3) 19 Jan-10 Feb 1984    0   (0.12)       0 (0.12)       0 (0.12)
4) 26 Mar-15 Apr 1984    0.1 (0.22)     0.2 (0.12)     0.1 (0.14)
5) 6 Jun-21 Jun 1994     1.6 (2.16)     1.0 (1.10)     0.6 (0.69)
6) 10 Sep-5 Oct 1984     0.9 (1.15)     0.2 (0.60)     1.0 (1.38)
7a) 8-9 Aug 2000         5.8 (11.8)     5.3 (10.66)    5.0 (10.01)
7b) 27 Sep-3 Oct 2000    6.8 (11.96)    6.1 (11.02)    5.9 (10.55)
Station Means: 1983-84   0.4 (0.56)     0.2 (0.36)     0.3 (0.44)
Station Means: 2000      6.3 (11.88)    5.7 (10.84)    5.5 (10.28)

              B. Temperature data ([degrees]C)

1) 19 Sep-6 Oct 1983        27.3           24.8           26.0
2) 31 Oct-16 Nov 1983       20.0           18.5           18.6
3) 19 Jan-10 Feb 1984        7.2            7.6            9.8
4) 26 Mar-15 Apr 1984       18.8           18.7           21.7
5) 6 June-21 June 1984      28.1           28.9           30.0
6) 10 Sep-5 Oct 1984        29.1           21.6           22.6
7a) 8-9 Aug 2000            32.1           31.2           30.9
7b) 27 Sep-3 Oct 2000       25.8           25.8           24.6

              C. Secchi disk readings (in cm)

1) 19 Sep-6 Oct 1983        31             31             34
2) 31 Oct-16 Nov 1983       37             28             23
3) 19 Jan-10 Feb 1984        3              4              3
4) 26 Mar-15 Apr 1984        9              7              8
5) 6 June-21 June 1984      31             32             30
6) 10 Sep-5 Oct 1984        53             49             52
7a) 8-9 Aug 2000           159            157            172
7b) 27 Sep-3 Oct 2000      169            200            214
Station Means: 1983-84      28             25             26
Station Means: 2000        164            179            193

     Period/Date           St. 4          St. 5          St. 6

    A. Salinity/Conductivity data (in parts per thousand and
                      microsiemens per cm)

1) 19 Sep-6 Oct 1983     0   (0.15)     0   (0.14)     0   (0.17)
2) 31 Oct-16 Nov 1983    0   (0.13)     0.3 (0.35)     0.1 (0.24)
3) 19 Jan-10 Feb 1984    0   (0.14)     0.1 (0.18)     0.1 (0.17)
4) 26 Mar-15 Apr 1984    0   (0.12)     0.1 (0.15)     0.4 (0.42)
5) 6 Jun-21 Jun 1994     0.8 (1.03)     0.9 (1.10)     1.1 (1.67)
6) 10 Sep-5 Oct 1984     0.6 (1.16)     1.4 (2.08)     1.0 (1.65)
7a) 8-9 Aug 2000         6.1 (12.25)    6.4 (12.68)    5.6 (11.23)
7b) 27 Sep-3 Oct 2000    5.8 (10.21)    6.2 (11.50)    6.5 (12.10)
Station Means: 1983-84   0.3 (0.49)     0.5 (0.67)     0.5 (0.78)
Station Means: 2000      6.0 (11.23)    6.3 (12.09)    6.1 (11.67)

              B. Temperature data ([degrees]C)

1) 19 Sep-6 Oct 1983        26.0           24.8           24.0
2) 31 Oct-16 Nov 1983       19.7           20.0           15.9
3) 19 Jan-10 Feb 1984        9.0            9.0            9.6
4) 26 Mar-15 Apr 1984       18.8           18.4           21.1
5) 6 June-21 June 1984      29.9           26.3           28.8
6) 10 Sep-5 Oct 1984        22.0           25.2           29.7
7a) 8-9 Aug 2000            31.3           31.1           30.8
7b) 27 Sep-3 Oct 2000       24.9           25.0           24.0

              C. Secchi disk readings (in cm)

1) 19 Sep-6 Oct 1983        26             21             28
2) 31 Oct-16 Nov 1983       11             37             20
3) 19 Jan-10 Feb 1984        4              8              4
4) 26 Mar-15 Apr 1984       10              9              4
5) 6 June-21 June 1984      67             34             32
6) 10 Sep-5 Oct 1984        57             22             41
7a) 8-9 Aug 2000           180            180            180
7b) 27 Sep-3 Oct 2000      189            115            146
Station Means: 1983-84      31             23             23
Station Means: 2000        185            148            163

     Period/Date           St. 7        Period mean

   A. Salinity/Conductivity data (in parts per
        thousand and microsiemens per cm)

1) 19 Sep-6 Oct 1983     0   (0.17)       0 (0.14)
2) 31 Oct-16 Nov 1983    0.2 (0.21)     0.1 (0.20)
3) 19 Jan-10 Feb 1984    0   (0.12)       0 (0.13)
4) 26 Mar-15 Apr 1984    0.1 (0.14)     0.1 (0.20)
5) 6 Jun-21 Jun 1994     1.0 (1.34)     1.0 (1.30)
6) 10 Sep-5 Oct 1984     0.8 (1.15)     0.9 (1.31)
7a) 8-9 Aug 2000         6.3 (12.62)    5.8 (11.61)
7b) 27 Sep-3 Oct 2000    7.1 (12.37)    6.3 (11.39)
Station Means: 1983-84   0.4 (0.59)
Station Means: 2000      6.7 (12.50)

       B. Temperature data ([degrees]C)

1) 19 Sep-6 Oct 1983        25.6           25.6
2) 31 Oct-16 Nov 1983       17.2           18.8
3) 19 Jan-10 Feb 1984        8.7            8.6
4) 26 Mar-15 Apr 1984       19.0           19.5
5) 6 June-21 June 1984      29.4           28.8
6) 10 Sep-5 Oct 1984        28.8           25.5
7a) 8-9 Aug 2000            31.5           31.3
7b) 27 Sep-3 Oct 2000       24.9           25.0

       C. Secchi disk readings (in cm)

1) 19 Sep-6 Oct 1983        26             28
2) 31 Oct-16 Nov 1983       16             26
3) 19 Jan-10 Feb 1984        2              4
4) 26 Mar-15 Apr 1984        5              8
5) 6 June-21 June 1984      30             37
6) 10 Sep-5 Oct 1984        38             44
7a) 8-9 Aug 2000           329            194
7b) 27 Sep-3 Oct 2000      373            201
Station Means: 1983-84      21
Station Means: 2000        351

TABLE 2A. Catfish species collected in Lake Maurepas.

                           By collection method (1983-1984):

                                        Multimesh    Large mesh
       Species           Otter Trawl    gill net      gill net

Ictalurus furcatus          2088           783           3
  Blue catfish
Ictalurus punctatus         1807            80           1
  Channel catfish
Pylodictus olivaris            1             0           0
  Flathead catfish
Ameiurus natalis               0             0           0
  Yellow bullhead
Ameiurus melas                 0             1           0
  Black bullhead
Noturus gyrinus                0             0           0
  Tadpole madtom
Bagre marinus                  1             7           0
  Gafftopsail catfish
Arius felis                    0             1           0
  Sea catfish

                         By collection method (1983-1984):

       Species                  Rotenone    Totals

Ictalurus furcatus                 0         2874
  Blue catfish
Ictalurus punctatus                8         1896
  Channel catfish
Pylodictus olivaris                8            9
  Flathead catfish
Ameiurus natalis                   6            6
  Yellow bullhead
Ameiurus melas                     0            1
  Black bullhead
Noturus gyrinus                    1            1
  Tadpole madtom
Bagre marinus                      0            8
  Gafftopsail catfish
Arius felis                        0            1
  Sea catfish

TABLE 2B. Catfish species collected in Lake Maurepas.

                                    By sampling period

                           Gear         1          2          3
                         Trawl or    Sep-Oct    Oct-Nov    Jan-Feb
       Species           Gillnet      1983       1983       1984

Ictalurus furcatus          T          366        321        555
  Blue catfish              G          123        201        123
Ictalurus punctatus         T           61        429        664
  Channel catfish           G            9         15          4
Pylodictus olivaris         T            0          0          1
  Flathead catfish          G            0          0          0
Ameiurus natalis            T            0          0          0
  Yellow bullhead           G            0          0          0
Ameiurus melas              T            0          0          1
  Black bullhead            G            0          0          0
Noturus gyrinus             T            0          0          0
  Tadpole madtom            G            0          0          0
Bagre marinus               T            0          0          0
  Gafftopsail catfish       G            0          0          0
Arius felis                 T            0          0          0
  Sea catfish               G            0          0          0

                                 By sampling period

                            4         5        6       7a
                         Mar-Apr    June    Sep-Oct    Aug
       Species             1984     1984     1984      2000

Ictalurus furcatus         573      143       130      130
  Blue catfish              80       71       185       --
Ictalurus punctatus        455       85       113        8
  Channel catfish           27       13        12       --
Pylodictus olivaris          0        0         0        0
  Flathead catfish           0        0         0       --
Ameiurus natalis             0        0         0        0
  Yellow bullhead            0        0         0       --
Ameiurus melas               0        0         0        0
  Black bullhead             0        0         0       --
Noturus gyrinus              0        0         0        0
  Tadpole madtom             0        0         0       --
Bagre marinus                0        0         1        0
  Gafftopsail catfish        0        0         7       --
Arius felis                  0        0         0        0
  Sea catfish                0        0         1       --

                         By sampling period

                            7b
                         Sep-Oct    Totals
       Species             2000     1983-84

Ictalurus furcatus          0        2088
  Blue catfish             --         783
Ictalurus punctatus         1        1807
  Channel catfish          --          80
Pylodictus olivaris         1           1
  Flathead catfish         --           0
Ameiurus natalis            0           0
  Yellow bullhead          --           0
Ameiurus melas              0           1
  Black bullhead           --           0
Noturus gyrinus             0           0
  Tadpole madtom           --           0
Bagre marinus               0           1
  Gafftopsail catfish      --           7
Arius felis                 0           0
  Sea catfish              --           1

TABLE 3. Catch per unit effort of Ictalurus furcatus in Lake Maurepas
(CPUE).

     Period Date          St. 1    St. 2    St. 3    St. 4    St. 5

            A. Trawl collections (number per 10 min. tow)

1) 19 Sep-6 Oct 1983      25.7     18.0     15.0     43.7      6.0
2) 31 Oct-16 Nov 1983      0       11.0     11.0     76.7      0.3
3) 19 Jan-10 Feb 1984     30.3     25.0     27.7     56.3     16.3
4) 26 Mar-15 Apr 1984     60.3     28.3     43.0     51.3      5.3
5) 6 June-21 June 1984     0        3.7     38.7      0.7      0
6) 10 Sep-5 Oct 1984       0        1.3      1.0      7.7     26.3
7a) 8-9 Aug 2000          10.3      1.7     11.0      4.7      6.3
7b) 27 Sep-3 Oct 2000      0        0        0        0        0

              B. Gill net collections (number per hour)

1) 19 Sep-6 Oct 1983       0.27     0.30     0.65     0.24     0.04
2) 31 Oct-16 Nov 1983      0.24     0.39     0.62     0.39     0.99
3) 19 Jan-10 Feb 1984      0.23     0.19     0.53     0.16     0.21
4) 26 Mar-15 Apr 1984      0.30     0.29     0.36     0.26     0.03
5) 6 June-21 June 1984     0.30     0.21     0.14     0.20     0.32
6) 10 Sep-5 Oct 1984       0.20     0.29     0.48     0.33     1.29

                                            Period
     Period Date          St. 6    St. 7     mean

  A. Trawl collections (number per 10 min. tow)

1) 19 Sep-6 Oct 1983       4.3      9.3      17.4
2) 31 Oct-16 Nov 1983      0.3      7.7      15.3
3) 19 Jan-10 Feb 1984     18.0     11.3      26.4
4) 26 Mar-15 Apr 1984      2.7       --      31.8
5) 6 June-21 June 1984     2.3      2.3       6.8
6) 10 Sep-5 Oct 1984       3.0      4.0       6.2
7a) 8-9 Aug 2000           7.7      1.7       6.2
7b) 27 Sep-3 Oct 2000      0        0         0

    B. Gill net collections (number per hour)

1) 19 Sep-6 Oct 1983       0.21     0.24      0.28
2) 31 Oct-16 Nov 1983      0.32     0.16      0.44
3) 19 Jan-10 Feb 1984      0.12     0.12      0.22
4) 26 Mar-15 Apr 1984      0.06     0.05      0.19
5) 6 June-21 June 1984     0.04     0.37      0.23
6) 10 Sep-5 Oct 1984       0.27     0.35      0.46

TABLE 4. Catch per unit effort of Ictalurus punctatus in Lake Maurepas
(CPUE).

     Period Date          St. 1    St. 2    St. 3    St. 4    St. 5

           A. Trawl collections (number per 10 min. tow)

1) 19 Sep-6 Oct 1983       0        0.7     12.3      1.0      1.0
2) 31 Oct-16 Nov 1983      0        1.3      2.0     79.7      0
3) 19 Jan-10 Feb 1984     30.3     15.3     31.3     98.3     14.7
4) 26 Mar-15 Apr 1984     46.0     26.0     32.0     42.3      2.0
5) 6 June-21 June 1984    18.7      6.0      0.3      0.7      1.0
6) 10 Sep-5 Oct 1984       5.3      0.3      0        0       30.6
7a) 8-9 Aug 2000           0        0.7      0.3      0.3      0.7
7b) 27 Sep-3 Oct 2000      0.3      0        0        0        0

             B. Gill net collections (number per hour)

1) 19 Sep-6 Oct 1983       0.05     0        0.06     0.02     0
2) 31 Oct-16 Nov 1983      0.07     0.02     0.03     0.03     0.02
3) 19 Jan-10 Feb 1984      0        0        0        0.01     0
4) 26 Mar-15 Apr 1984      0        0.13     0.09     0.11     0.09
5) 6 June-21 June 1984     0        0        0.09     0.05     0.10
6) 10 Sep-5 Oct 1984       0        0        0.03     0        0.13

                                            Period
     Period Date          St. 6    St. 7     mean

  A. Trawl collections (number per 10 min. tow)

1) 19 Sep-6 Oct 1983       2.3      3.0       2.9
2) 31 Oct-16 Nov 1983      9.7     50.3      20.4
3) 19 Jan-10 Feb 1984     10.7     20.7      31.6
4) 26 Mar-15 Apr 1984      3.3       --      25.3
5) 6 June-21 June 1984     0.7      1.0       4.1
6) 10 Sep-5 Oct 1984       0.3      1.0       5.4
7a) 8-9 Aug 2000           0        0.7       0.4
7b) 27 Sep-3 Oct 2000      0        0         0.1

    B. Gill net collections (number per hour)

1) 19 Sep-6 Oct 1983       0        0.01      0.02
2) 31 Oct-16 Nov 1983      0.05     0.02      0.03
3) 19 Jan-10 Feb 1984      0.01     0.03      0.01
4) 26 Mar-15 Apr 1984      0.02     0.02      0.07
5) 6 June-21 June 1984     0.04     0         0.04
6) 10 Sep-5 Oct 1984       0        0.05      0.04

TABLE 5. Condition factor for catfishes in Lake Maurepas (1983-84)

                                      100-200    200-300    300-400
     Period/Date          < 100 mm      mm         mm         mm

                       A. Ictalurus furcatus

1) 19 Sep-6 Oct 1983        0.72       0.81       0.91       0.87
2) 31 Oct-16 Nov 1983       0.75       0.71       0.82       0.85
3) 19 Jan-10 Feb 1984       0.77       0.77       0.84       0.90
4) 26 Mar-15 Apr 1984       0.72       0.76       0.84       0.91
5) 6 June-21 June 1984      0.78       0.76       0.90       0.90
6) 10 Sep-5 Oct 1984         --        0.72       0.74       0.81

                      B. Ictalurus punctatus

1) 19 Sep-6 Oct 1983        0.89       0.77       0.86        --
2) 31 Oct-16 Nov 1983       0.73       0.68       0.83        --
3) 19 Jan-10 Feb 1984       0.80       0.75       0.85        --
4) 26 Mar-15 Apr 1984       0.77       0.74       0.87       1.20
5) 6 June-21 June 1984      0.78       0.74       0.90       1.01
6) 10 Sep-5 Oct 1984         --        0.78       0.89        --

                          400-500
     Period/Date             mm

      A. Ictalurus furcatus

1) 19 Sep-6 Oct 1983        0.91
2) 31 Oct-16 Nov 1983       0.92
3) 19 Jan-10 Feb 1984       1.00
4) 26 Mar-15 Apr 1984       0.97
5) 6 June-21 June 1984      1.00
6) 10 Sep-5 Oct 1984        0.86

     B. Ictalurus punctatus

1) 19 Sep-6 Oct 1983
2) 31 Oct-16 Nov 1983
3) 19 Jan-10 Feb 1984
4) 26 Mar-15 Apr 1984
5) 6 June-21 June 1984
6) 10 Sep-5 Oct 1984

ACKNOWLEDGMENTS

D.A. Turner and R.G. Thomas completed most of the fieldwork and laboratory processing of collections during 1983-1984, and thus contributed significantly to the completion of this study. The project was part of a baseline study funded by the Coastal Energy Impact Program, NOAA Grant Number NA-83-AAA-D-CZ025, and administered through the Louisiana Department of Natural Resources Coastal Management Division, G.W. Childers, Principal Investigator. Mars Stouder, Danica Bailey, and Tom Blanchard helped with sampling in 2000.

LITERATURE CITED

CARLANDER, K.D. 1969. Handbook of freshwater fishery biology, Vol. 1. Iowa State Univ. Press, Ames, Iowa. 752 pp.

CHILDERS, G.W. 1985. A baseline study of the water quality and selected faunal communities in Lake Maurepas, its major tributaries, and Pass Manchac. Final report to Louisiana Department of Natural Resources, Coastal Zone Management Division. 330 pp.

DAVIS, J.T., B.J. FONTENOT, C.E. HOENKE, A.M. WILLIAMS, AND J.S. HUGHES. 1970. Ecological factors affecting anadromous fishes of Lake Pontchartrain and its tributaries. Louisiana Wildlife and Fish. Comm., Fisheries Bull. No. 9. 63 pp.

LAICHE, G.S. 1980. The fishes of the Amite River drainage in Mississippi and Louisiana. M.S. Thesis. University of New Orleans, New Orleans, Louisiana. 103 pp.

HASTINGS, R.W., D.A. TURNER, AND R.G. THOMAS. 1987. The fish fauna of Lake Maurepas, an oligohaline part of the Lake Pontchartrain estuary. Northeast Gulf Sci. 9(2):89-98.

PERRY, W.G. AND A. WILLIAMS. 1986. A note on size differences of channel catfish, Ictalurus punctatus, collected from southwest and southeast Louisiana, Proc. Louisiana Acad. Sci. 49:45-52.

SAUL, G.E. 1974. Ichthyofaunal investigation of the Tickfaw River drainage basin. M.S. Thesis. Louisiana State University, Baton Rouge, Louisiana. 53 pp.

SIKORA, W.B. AND B. KJERVE. 1985. Factors influencing the salinity regime of Lake Pontchartrain, Louisiana, a shallow coastal lagoon: Analysis of a long-term data set. Estuaries 8 (2A): 170-180.

TARVER, J.W. AND L.B. SAVOIE. 1976. An inventory and study of the Lake Pontchartrain-Lake Maurepas estuarine complex. Phase II--Biology. Louisiana Wildlife and Fish. Comm., Techn. Bull. No. 19:7-99.

THOMPSON, B.A. AND J.S. VERRET. 1980. Nekton of Lake Pontchartrain, Louisiana, and its surrounding wetlands. Ch. 12. Pp. 711-864. In J.H. Stone (Ed.), Environmental analysis of Lake Pontchartrain, Louisiana, its surrounding wetlands, and selected land uses. Publ. No. LSU-CEL-80-08, Coastal Ecology Laboratory, Center for Wetland Resources, Louisiana State University, Baton Rouge, Louisiana.

WATSON, M.B., C.J. KILLEBREW, M.H. SCHURTZ, AND J.L. LANDRY. 1981. A preliminary survey of Blind River, Louisiana. Pp. 303-319. In L.A. Krumholz (Ed.), The warm water streams symposium. A national symposium on fisheries aspects of warmwater streams. Southern Division, American Fisheries Society, Knoxville, Tennessee.

Robert W. Hastings
Turtle Cove Environmental Research Station
Southeastern Louisiana University
Hammond, LA 70402

Robert W. Hastings, Current address: Alabama Natural Heritage Program, Huntingdon College, Montgomery, AL 36106.