Browsing by Author "Johnson, Roy B."
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Item Evaluation of the Effects on Fin-Fish Populations of Opening the Port Mansfield Channel in the Lower Laguna Madre - Analysis of Populations of Sports and Commercial Fin-Fish and of Factors Which Affect These Populations in the Coastal Bays of Texas(Texas Parks and Wildlife Department, 1964) Johnson, Roy B.The opening of Port Mansfield Pass appears to have increased the bay populations of pinfish, Lagodon rhomboides, in the summer, and anchovies, Ancho sp., in the winter. No relation was found between the opening of the pass and the abundance of grooved shrimp, Penaeus aztecus and P. durorarum. There was evidence that Port Mansfield Pass was used by adult southern flounder, Paralichthys lethostigma; adult redfish, Sciaenops ocellata; post-larval and juvenile penaeid shrimp; and by blue crabs, Callinectes sapidus, of all stages. A general decrease in the numbers of fish and shrimp in trawl samples was noted in 1963, probably due to large quantities of dead, wind-rowed vegetation at many of the stations and to high salinities in the Port Mansfield area. Port Mansfield Pass was ineffective in reducing or stabilizing salinities in the area.Item Hydrographic and Meteorological Study of the Lower Laguna Madre - Analysis of Populations of Sports and Commercial Fin-Fish and of Factors Which Affect These Populations in the Coastal Bays of Texas(Texas Parks and Wildlife Department, 1965) Johnson, Roy B.Water surface temperatures were relatively low in the spring of 1964 due to abnormally low air temperatures in late February and unusually high in November and December. Two days with below freezing temperatues were recorded in February. Rainfall was 11.0 inches below normal in 1964 compared to 8.0 inches below normal in 1963. Salinities were generally higher than in 1963, but were lower in 1964 during early summer. Salinities below 40.0 ppt were recorded from the north end of the bay for the first time since August 1962.Item Hydrographic and Meteorological Study of the Lower Laguna Madre - Analysis of Populations of Sports and Commercial Fin-Fish and of Factors Which Affect These Populations in the Coastal Bays of Texas(Texas Parks and Wildlife Department, 1964) Johnson, Roy B.Average monthly air and water temperatures ranged from a low of 9.6 degrees C. in January to a high of 30.8 degrees C. in September, increasing rapidly after February and decreasing after November. Average monthly air temperature ranged from a low of 12.4 degrees C. in December to a high of 29.4 degrees C. in August. Monthly rainfall totals were lowest in April (0.05 inches) and highest in May (4.51 inches). Hurricane Cindy produced moderate rainfall in September. The total rainfall was 8.03 inches below normal. Salinities were high throughout the bay in 1963, due to a combination of rainfall shortage, low tides, high evaporation, and influx of high salinity water from the upper Laguna Madre. Tides were highest from April through June and from late September through November. Southeast winds produced high tides during the summer and Hurricane Cindy produced abnormally high tides during September. Normal low tides occurred during the winter.Item Life History Study of the Commercial Oyster in the Lower Laguna Madre - Survey of Oyster Populations and Associated Organisms(Texas Parks and Wildlife Department, 1964) Johnson, Roy B.South Bay oyster population samples of one standard bushel (culled of dead shell) contained a low of 27 market oysters in January and a high of 116 market oysters in May. Market oysters were generally small in size. A peak spat set occurred in May to July, 1963, as indicated by data from population samples and spat collectors. This peak occurred after a rise in temperature and during a period of reduced salinities in the bay. Growth rates averaged 2.8 millimeters per month for market oysters and 5.4 millimeters per month for seed oysters. Oysters grew faster during the spring and winter. Condition rates indicated that market oysters were in poor condition during the fall of 1963, possibly due to unusually high salinities. There was no incidence of Dermocystidium marinum.Item Population Studies of the Blue Crabs of the Lower Laguna Madre - Studies of the Blue Crab Populations of the Texas Coast(Texas Parks and Wildlife Department, 1965) Johnson, Roy B.Blue crabs, Callinectes sapidus, Rathbun, were collected at various locations in the bay with otter trawl, 60-foot seine and trammel net. The largest numbers of juvenile crabs per trawl sample occurred during February and December. Crabs were most abundant in seine samples from April through October. The abundance of adult crabs was highest during the spring and fall, as indicated by trammel net catches. The movement of adult crabs was related to temperature and salinity. Mating occurred during late spring and early summer. This was indicated by the presence of large percentage of female crabs in the bay and the capture of "doublers". Two waves of juvenile crabs entered the bay in 1964. The first wave was detected in February; the second was detected in October. Both groups entered the bay when water temperatures were below 25.0 degrees C. and salinities were above 40.0 ppt.Item Population Studies of the Blue Crabs of the Lower Laguna Madre - Studies of the Blue Crab Populations of the Texas Coast(Texas Parks and Wildlife Department, 1964) Johnson, Roy B.Blue crabs were sampled with an otter trawl, minnow seine and trammel net at various locations in the lower Laguna Madre. A net of one millimeter mesh was used to sample larval crabs in the surf. Poor catches of juvenile blue crabs by otter trawl in the first part of the 1963 study period were probably due to an unsuccessful spawn reported in 1962. Indications were that mating occurred from April through July, and during October, 1963. A successful spawn occurred in late fall of 1963, as evidenced by an increase of larvae in beach samples in November, and by the prevalence of small juvenile crabs in the bay in November and early December.Item Study of the Juvenile Shrimp Populations of the Lower Laguna Madre - Study of the Texas Shrimp Populations(Texas Parks and Wildlife Department, 1965) Johnson, Roy B.Grooved shrimp, Penaeus aztecus and P. duorarum, reached peak abundance in the bay in April, May, June, August and November 1964. Three waves were detected. The first and largest wave appeared in early April. Cool water temperatures and decreasing salinities influenced a large-scale emigration of these shrimp in mid-May. The second wave appeared in early August, and left trawl stations in September. The third wave was detected in late October. This group was present in samples through December. Grooved shrimp were more abundant in summer and fall of 1964 than in 1963, but were less abundant during spring. A 46 per cent decrease in the overall trawl catch was observed in 1964. White shrimp, P. setiferus; were present in samples from June through November 1964. The major wave of white shrimp was detected in mid-June. These shrimp left the bay in mid-July, were greater in 1964 than in 1963.Item Study of the Juvenile Shrimp Populations of the Lower Laguna Madre - Study of the Texas Shrimp Populations(Texas Parks and Wildlife Department, 1964) Johnson, Roy B.Grooved shrimp, Penaeus aztecus and P. duorarum, were present in samples from early April through December and were most abundant from April through May. The first and most abundant wave of shrimp occurred in early April. Smaller waves occurred during May, August, and September with continuous recruitment during most of the study period. A growth rate of 0.6 mm per day was indicated in the secondary bay area with shrimp leaving the secondary stations near 75 mm. A growth rate of about 1.3 mm per day was indicated in the tertiary area with shrimp leaving the station below 90 mm in length. The largest numbers of grooved shrimp occurred slightly earlier in 1963 than in 1962, but remained abundant for a shorter period of time. Averaged monthly samples showed a 40 percent decrease in numbers from 1962. White shrimp, P. setiferus, were taken from late May through December, and were most abundant from June through August. White shrimp were abundant only in shallow, muddy areas, and grew at approximately 1.7 mm per day in tertiary areas. Most shrimp left the bay when approximately 100 mm long. White shrimp were present in the bay during the same periods in 1962 and 1963, but were only 15 percent as abundant in 1963