Bay scallops, Argopecten irradians, in the northwestern Gulf of Mexico (Alabama, Mississippi, Louisiana, and Texas).
|Abstract:||There is no evidence that a commercial bay scallop fishery exists anywhere in the northwestern Gulf of Mexico. No data concerning scallop abundance or distribution was found for Alabama, Mississippi, and Louisiana. Texas is the only state west of Florida where bay scallop populations have been documented. These records come from a variety of literature sources and the fisheries-independent data collected by Texas Parks and Wildlife Department (1982-2005). Although common in the diet of prehistoric peoples living on the Texas coast, recent (last ~50 years) bay scallop population densities tend to be low and exhibit "boom-bust" cycles of about 10-15 years. The Laguna Madre, is the only place on the Texas coast where scallops are relatively abundant, this is likely due to extensive seagrasses cover (>70%) and salinities that typically exceed 35 psu. The lack of bay scallop fishery development in the northwestern Gulf of Mexico is probably due to variable but generally low densities of the species combined with a limited amount of suitable (i.e. seagrass) habitat.|
Freshwater ecology (Research)
|Publication:||Name: Marine Fisheries Review Publisher: Superintendent of Documents Audience: Academic Format: Magazine/Journal Subject: Agricultural industry; Business Copyright: COPYRIGHT 2009 U.S. Department of Commerce ISSN: 0090-1830|
|Issue:||Date: Summer, 2009 Source Volume: 71 Source Issue: 3|
|Topic:||Event Code: 310 Science & research|
|Geographic:||Geographic Scope: Louisiana; Texas Geographic Code: 0GULF Gulf of Mexico; 1U7LA Louisiana; 1U7TX Texas|
Two subspecies of bay scallops inhabit the northwestern Gulf of Mexico coast: Argopecten irradians concentricus on the west coast of Florida to the Chandeleur Islands, Lousiana, and A. i. amplicostatus from Galveston Bay, Texas, south to northern Mexico. Abundance of bay scallops in the northwestern Gulf is typically much lower than on the west coast of Florida and the Atlantic coast. Alabama, Mississippi, and Louisiana have not reported a commercial scallop catch since harvest statistics began being published in 1950. (1) Texas reported its only commercial catches (since 1895) in 1984 and 1985 (Culbertson et al., 2004). The landings for both years combined were 2.4 metric tons (t) with a market value of $2,746.00. In the same years, 13,437 t of bay scallops with a total value of $35,842.00 were landed in Florida. (1) Texas is the only state in the northwestern Gulf that regulates recreational harvesting of scallops (TPWD, 2002, 2006). Scallops can only be harvested from waters approved by the Texas Department of Health. They can be taken year-round by hand, using dip nets, rakes, or dredging and there are no size or bag limits.
Since there is no fishery on the northwestern Gulf of Mexico, this paper will focus on what is known about past and present bay scallop distribution and abundance in the northwestern Gulf (primarily Texas, Fig. 1) and the-reasons why a commercial fishery is unlikely to develop.
Prehistoric Scallop Usage
Shell middens composed primarily of eastern oyster, Crassostrea virginica, or rangia, Rangia cuneata and/or R. flexuosus, shells are common along much of the northwestern Gulf of Mexico coast. The predominant species depends on whether they were deposited in low salinity areas near river deltas and bay heads (rangia), or in areas of higher salinity closer to the Gulf along bay margins and barrier islands (oysters). Texas shell middens usually represent sites of repeated seasonal occupation (Ricklis, 1995), but on the Louisiana Chenier plain, middens can be difficult to separate from natural accumulations of shell (Henderson et al., 2002).
Scallops do not appear in middens from Louisiana (e.g. Poverty Point Site; Gagliano and Saucier, 1963) but they are a common component of middens in northwestern Florida (Russo and Quitmyer, 1996) and Texas (Table 1). We could find no record of marine/estuarine shell middens or bay scallop artifacts in either Mississippi or Alabama. Rangia or freshwater forms dominate the few middens in Louisiana that have been studied (Henderson et al., 2002), suggesting that estuarine salinities may have been too low outside of Texas and Florida to support large prehistoric scallop populations.
Bay scallops are one of five species of marine/estuarine mollusks that were exploited by prehistoric inhabitants of the Texas coastline. Their shells are often co-dominant with oyster shells (Ricklis, 1995), but they are not usually associated with middens dominated by rangia shells. Bay scallops are infrequently found in middens on the upper Texas coast and are much more abundant from Matagorda Bay southward (Steele, 1987; Table 1). The majority of bay scallop shells found in archeological sites are unmodified, even articulated, and in large enough quantities to suggest they were a significant and integral food source (Steele, 1987; Ricklis, 1996). Scallops were apparently not used for tools or ornaments since possibly modified shells were only found at two sites (Steele, 1987).
Bay scallops are most abundant in middens that date to the early Archaic period (~7500-4500 YBP). At that time, barrier islands had not yet formed off the Texas coast, and estuaries were open with unrestricted exchange with the Gulf of Mexico. Shellfish were a seasonally (fall, winter, early spring) important source of both calories and protein, and exploitation was fairly intense. At the Holmes Site on Corpus Christi Bay, scallop shells dominated the deposit and were abundant enough to have yielded an estimated 15,750 g of meat (Ricklis, 1996).
[FIGURE 1 OMITTED]
After the barrier islands formed (~4000YBP), fish and mammal remains dominate midden assemblages. Shellfish remains are much less abundant in middens deposited after ~3000YBP (late Archaic). Changing salinities in the newly enclosed bays, concomitant changes in shellfish species composition and abundance, technological advancements, and increasing human populations probably all contributed to reduced importance of shellfish exploitation in the estuaries and greater reliance on fishing and hunting. However, shellfish remained a part of the diet of the native peoples up through historic times. Cabeza de Vaca (early 1500's) and De Bellisle (early 1700's), two early explorers of the Texas Coast, observed opportunistic and deliberate harvest of shellfish, including scallops (Newcomb, 1961).
Recent Abundance and Distribution
Our review of the literature turned up no mentions of living or dead bay scallops in Louisiana, Mississippi, or Alabama. Queries to fishing guides in the Chandeleur Islands area of Louisiana yielded sightings of bay scallop shells, but no reports of live scallops. In Texas, two sources of data for scallop abundance and distribution are available for evaluation: a variety of published and unpublished literature and reports (1894-2006) and quantitative, coastwide fisheries independent monitoring data collected by the Texas Parks and Wildlife Department (TPWD) for 1982-2005.
An exhaustive review of the literature for Texas turned up 40 sources with references to bay scallop distribution and abundance (Table 2). These ranged from reports or counts of dead shell in samples (Powell et al., 1982; Smith, 1985; White et al., 1985-89), and men dons in species checklists (Evermann and Kendall, 1894; Holland et al., 1974), to more quantitative studies that provide a qualitative estimate of abundance (Ladd, 1951), data that allows a reasonable estimation of local abundance, frequency, or both (Hildebrand and King, 1973-79) or samples were taken such that scallops could or should have been collected, but were not (Calnan, 1980; White et al., 1985-89).
Most records represent collections at only one or a few sites within a single bay system. The only comprehensive studies were those by the Bureau of Economic Geology in the mid to late 1970's. Composition and abundance of benthic fauna were included in comprehensive studies of the bottoms on "submerged lands" of the bays and inner shelf of the Texas coast (White et al., 1985-89). Studies focused on shoalgrass, Halodule wrightii, beds (Corpus Christi Bay, Laguna Madre), and turtlegrass, Thalassic testudinum, beds (Redfish Bay) yielded the majority of scallop records.
The upper Laguna Madre has been studied more than the other bays and has a more complete record of when scallops have been present. During 1976-77 when all bays were sampled, live scallops were only found in Aransas Bay and upper Laguna Madre. Scallops were abundant in areas of Aransas Bay and lower Laguna Madre in the 1950's, and in parts of upper Laguna Madre in 1975-77 and 2004-05.
TPWD Independent Fisheries Data
Since 1982, nekton have been sampled in each Texas bay system using bag seines and trawls. Both of these gears will also capture bay scallops and, when collected, their numbers and sizes have been recorded. Bay systems are divided into grids, grids are stratified by depth (trawls vs. bag seines), and 20 grids are randomly chosen from each stratum prior to each sampling event. A sampling station within the grid is randomly chosen. No grid can be sampled more than once per month with the same gear. We obtained bag seine and trawl data for 1982-2005 from the Texas Parks and Wildlife's Coastal Fisheries Division, as described in Martinez-Andrade et al. (2005).
Very few scallops were collected in bag seines in any bay (Table 3). Scallops were not collected from Sabine Lake or the Galveston Bay system in either bag seines or trawls. The majority of scallops were collected in trawls in the upper Laguna Madre (Table 4). Trawls outside the Laguna Madre yielded few scallops and from 1991-98 no scallops were collected in trawls from any bay except lower Laguna Madre. Scallops were most abundant in 1987-88 and 2004; more than 95% of these were trawled from the upper Laguna Madre.
Scallops collected in bag seines were largest (mean length 43.4 mm) in Corpus Christi Bay and smallest (mean length 27.9 mm) in upper Laguna Madre (Table 5). Scallops trawled from Aransas and San Antonio bay systems were generally larger than those from other bay systems (Table 6). Average length (San Antonio Bay = 39.9 mm; Aransas Bay = 43.3 mm) of scallops in these two systems was larger than on the rest of the coast and was slightly larger than seined scallops in the same bays. Average shell lengths of scallops trawled from Corpus Christi Bay and the Laguna Madre were smaller than the average of seined specimens.
During 2004, shell length, width, and dry weight as well as scallop body dry weight were determined on a sample of 10 bay scallops collected from Bird Island Basin in upper Laguna Madre. (2) These scallops were collected during November from shoalgrass in water about 1.25 m deep. Average shell length was 53.9 mm (SD=7.2), average width was 55.2 mm (SD=7.7), and average dry weight was 23.5 g (SD=6.1). Average length of this collection was nearly double the average length of scallops in TPWD trawls during the same year. Average body dry weight was 23.5 g (SD=6.1).
Based on TPWD trawl data, scallop distribution and abundance on the Texas coast appears linked to salinity and fluctuations in salinity. Virtually all scallops were collected from waters of at least 20 psu (Fig. 2). The vast majority of scallops were collected in the hypersaline Laguna Madre (Fig. 3), especially the upper lagoon, which tends to exhibit higher salinities than the lower lagoon. When all data from coastal bays were analyzed using Spearman's rho there was a significant positive correlation between salinity and scallop abundance (correlation coefficient = 0.073; p = 0.0001; n= 22,998). However, the same analysis using data only from Laguna Madre yielded a negative correlation (correlation coefficient = -0.035; p = 0.009; n = 5,682). Boom years in the upper Laguna Madre generally followed years when mean annual salinity dropped to around 30 psu (Fig. 4, top). During the 1990's, a persistent brown tide in the upper Laguna Madre may have prevented a boom year following the 1992-93 salinity declines or salinities may have declined below the threshold for recruitment. In the lower Laguna Madre, scallop abundance is low but the population appears to be more consistent than in the upper lagoon (Fig. 4, bottom). "Boom" abundances (e.g. 1992, 2000) are less than 10% of boom abundances in the upper lagoon, and the pattern of increasing abundance following declining salinity is not clear.
We were unable to find any records of abundance or distribution of scallops in the northwestern Gulf of Mexico outside of Texas. Fisheries-independent trawl bag seine data and other records from Texas show that scallops appear to "boom" from Aransas Bay south at intervals of about 10-15 years (i.e. 1950's, Aransas Bay; 1967, Redfish Bay; 1976-78, 1987-1988, and 2004, upper Laguna Madre). In lower Laguna Madre, scallop populations have periodically boomed (i.e. 1950's) but they may be present in low numbers more consistently than in other bays. The only year between 1987-2005 that no scallops were trawled from the lower Laguna Madre was 1997. Recruitment limitations may be responsible for "boom-bust" cycles of abundance in bay scallops (Peterson and Summerson, 1992). A recruitment study in the upper Laguna Madre during 2005-06, the year after a boom, yielded no scallop spat from 28 stations and only three adults (Hubner, 2007) suggesting that this is casein the upper Laguna Madre.
The lack of bay scallop fishery development in the northwestern Gulf of Mexico is doubtless due to variable but generally low densities of the species combined with a limited amount of suitable (i.e. seagrass) habitat. Bay scallop distribution is closely tied to seagrass distribution (Gutsell, 1930; Marshall, 1947; Eckman, 1987; Ambrose and Irlandi, 1992) and the majority of seagrasses in the northwestern Gulf are found in Texas (Table 7). Seagrass cover in Texas is inversely related to freshwater inflow and increases from north to south. The majority of Texas seagrasses (~79%) are found in the semi-arid and hypersaline Laguna Madre, with over 75,000 ha (Pulich, 1999) and greater than 70% overall coverage (Onuf, 1995). Shoalgrass is the dominant species but turtlegrass, manatee grass, Cymodocea filiforme, and small amounts of clover grass, Halophila engelmannu, and widgeon grass, Ruppia maritima, are also found in the system. Seagrasses fringe the shorelines of other bays (e.g. Corpus Christi Bay, Aransas Bay). Galveston Bay was the only other bay on the Texas coast where seagrasses had been fairly extensive, but by 1989 very little remained (Pulich, 1999). Recent reintroduction of seagrasses into the bay may reverse this trend.
Submerged aquatic vegetation is found in the bays and sounds of the northern Gulf (e.g. Mobile Bay, Mississippi Sound, Lake Ponchartrain), but is often dominated by freshwater species such as wild celery, Valisnera, and widgeon grass. Never widespread, where shoalgrass is currently present in Alabama, coverage is much reduced from historic levels (Barry Vittor and Associates, Inc., 2005). Small amounts of seagrasses (primarily shoalgrass and manatee grass) are found on the northern sides of barrier islands in Mississippi (Handley, 1995). Losses were estimated at more than 66% from 1956 to 1992.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
In Louisiana, seagrasses have been completely lost in the Mississippi Delta, behind the south coast barrier islands, and in the coastal lakes. Chandeleur Sound, an area that is mostly unaffected by human impacts, is the only part of Louisiana where seagrasses are still present. The lack of seagrasses over much of the northwestern Gulf, due largely to low average salinities and high turbidity (Handley, 1995), accounts for the lack of scallop records north of Matagorda Bay, Texas.
[FIGURE 4 OMITTED]
Another component to add to the complexity of bay scallop abundance patterns in Texas was the persistent and continuous brown-tide bloom in the upper Laguna Madre from 1990-98 (Montagna et al., 1993). The freeze of 1989 and subsequent brown tide have been anecdotally blamed for the absence of bay scallops in the upper Laguna Madre throughout much of the 1990's. Brown tides have plagued New England estuarine complexes since the 1970's and have been implicated in decline of bivalve populations, including the bay scallop (Bricelj and Lonsdale, 1997). The algal blooms affect scallop populations by: 1) reducing the efficiency of filter feeding in adults (Cosper et al., 1989); 2) limiting food sources for larval scallops (Gallager et al., 1989); 3) gamete resorption in reproductive adults (Tracey, 1988); and 4) habitat loss due to increased turbidities (Tettelbach and Wenczel, 1993). Light attenuation from the Texas brown tide had caused a loss of ~940 ha of seagrass cover in the upper Laguna Madre by 1995 (Onuf, 1996) and the bloom continued unabated for another 3 years. Feeding by adult grazers, such as dwarf surfclam, Mulinia lateralis, was apparently unaffected by the bloom (Montagna et al., 1993). However, both growth rates and swimming speed were reduced in the larvae of the polychaete Streblospio benedicti supporting the hypothesis that reduced populations of benthic organisms were caused by sublethal effects on larvae (Ward et al., 2000).
Although the brown tide may have impacted bay scallop populations in the upper Laguna Madre, they were also absent from other bays that did not experience brown tides during the same period of time (e.g. Corpus Christi Bay, Aransas Bay). In addition, scallops were present in the lower Laguna Madre during nearly every year of the 1990's. It seems just as likely that the absence of bay scallops in the upper Laguna Madre 1991-97 was due to natural variability, rather than the direct or indirect impacts of the brown tide.
In conclusion, the low and variable abundance of bay scallops in Texas coastal bays and their apparent rarity in the bays along the rest of the northwestern Gulf precludes development of a fishery. In Texas, scallops are most abundant in the Laguna Madre, where seagrass cover is extensive and where salinities generally exceed 35 psu. Boom-bust population cycles are the norm in most bays, but especially in upper Laguna Madre, with booms occurring at intervals of 10-15 years over the last 60 years, based on the available data. This pattern suggests that Texas bay scallops are recruitment limited and that exogenous larval inputs must be very low.
We appreciate Clyde MacKenzie's invitation to write this paper, and his willingness to spearhead the effort to thoroughly review the status and trends of bay scallops in North America. Thanks to Jim Tolan of Texas Parks and Wildlife for providing the fisheries-independent data we analyzed for this paper. Wes Tunnell reviewed an early version of the manuscript and his comments helped improve the final product. Clyde MacKenzie and Willis Hobart also provided constructive reviews. The Center for Coastal Studies at Texas A&M University-Corpus Christi provided support to the senior author during the preparation of this manuscript.
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(1) Landings statistics have been published by the National Marine Fisheries Service, NOAA, in various issues of the Current Fisheries Statistics series
(2) Hubner, M., and K. Withers. Texas A&M University-Corpus Christi, 6300 Ocean Dr., Unit 5866, Corpus Christi, TX. Unpubl. data on file at the Center for Coastal Studies.
Kim Withers and Matt Hubner are with the Center for Coastal Studies, Texas A&M University-Corpus Christi, 6300 Ocean Dr., Unit 5866, Corpus Christi, TX 78412 (email: Kim. Withers@tamucc.edu).
Table 1.--Occurrences of bay scallops in archeological contexts on the Texas Gulf Coast. Site Name Bay or Number Date Galveston Bay Multiple Not available Lavara Bay Multiple Not available Matagorda Bay Multiple Not available Copano Bay 41AS5 2740-2500YBP (1) 41AS15 Archaic-prehistoric 41AS3 2764-2727YBP (1) Aransas Bay Johnson Site Archaic Nueces Bay 41SP15 5257-875YBP (1) 41SP153 Unit 1 7509-9857YBP (1) 41 SP153 Area 2 5888-568 YBP (1) 41SP156 5592-614YBP (1) 41SP177 3156-2873YBP (1) Corpus Christi Bay 41SP120 South Block 1161-730YBP (1) 41SP120 North Block 1338-741 YBP (1) 41SP11 626-533YBP (1) 41 NU65 Archaic-prehistoric 41 NU101 Archaic-prehistoric 41 SP43/120 Archaic Laguna Madre Multiple sites Not available Baffin Bay 41 KL13 Archaic-prehistoric 41 KL71 4552[+ or -]60YBP (2) 41 KL37 Archaic Site Name Bay or Number Remarks Galveston Bay Multiple Bay scallop present in middens, but not abundant Lavara Bay Multiple Bay scallop present in middens Matagorda Bay Multiple Bay scallop absent from middens Copano Bay 41AS5 Bay scallops present in midden 41AS15 Bay scallops were ~2% of 183 kg of shell 41AS3 Bay scallops common Aransas Bay Johnson Site Bay scallops common Nueces Bay 41SP15 Dense oyster & bay scallop 41SP153 Unit 1 Dense oyster & scallop 41 SP153 Area 2 Dense oyster & bay scallop 41SP156 Dense oyster & bay scallop 41SP177 Moderate oyster, some bay scallop Corpus Christi Bay 41SP120 South Block Dense mixed shell midden (oyster, bay scallop, quahog, whelk, others) 41SP120 North Block Dense mixed shell midden (oyster, bay scallop, whelk, quahog, others) 41SP11 Scattered shell, including bay scallop 41 NU65 2 bay scallop shells recovered 41 NU101 2 bay scallop shells recovered 41 SP43/120 2,000 fragments, bay scallop 2nd to oyster in abundance Laguna Madre Multiple sites Bay scallop present Baffin Bay 41 KL13 Bay scallop and other shell present on surface 41 KL71 Midden contained oyster, whelk, tulip shell, and bay scallop 41 KL37 Whelk, oyster, bay scallop, and tulip shell scatter Site Name Bay or Number Source Galveston Bay Multiple Steele, 1987 Lavara Bay Multiple Steele, 1987 Matagorda Bay Multiple Steele, 1987 Copano Bay 41AS5 Ricklis and Albert, 2005 41AS15 Prewitt and Paine, 1987 41AS3 Ricklis, 1995 Aransas Bay Johnson Site Shafer and Bond, 1985; Campbell, 1947 Nueces Bay 41SP15 Ricklis and Cox, 1991 41SP153 Unit 1 Ricklis, 1993 41 SP153 Area 2 Ricklis, 1993 41SP156 Ricklis, 1993 41SP177 Ricklis, 1993 Corpus Christi Bay 41SP120 South Block Ricklis and Cox, 1991 41SP120 North Block Ricklis, 1993 41SP11 Ricklis, 2006 41 NU65 Steele and Mokry, 1985 41 NU101 Steele and Mokry, 1985 41 SP43/120 Ricklis, 1987 Laguna Madre Multiple sites Steele, 1987 Baffin Bay 41 KL13 Hester, 1971 41 KL71 Smith, 1986 41 KL37 Smith, 1986 (1) These dates represent age before present (YBP) calibrated 1-sigma age ranges (Ricklis, 1995). (2) This date is an uncorrected radiocarbon date on charcoal from the site (Smith, 1986). Table 2.--Occurrences and estimated abundance of bay scallops in bays along the Texas Gulf Coast compiled from various published and unpublished sources. Bay Scallop Occurrence/Estimated Year SL GB MB ES SA AB CB RB CC NB ULM LLM 1894 D P 1940 C 1951-58 R VA R VA 1959-60 R 1967 A (1) 1968 R 1971-73 O 1973-74 P P O 1974-75 R-C O 1975-76 D O 1976-77 0 D D D D R D D D O 0-VA O 1977-78 O R-C P 1980 D 1981-82 R R 1984 D D 1986-87 F C 1989-90 O O O 1992-93 O O 2001-02 R O 2004 A 2005 C-A C 2006 R Year Sources 1894 Evermann and Kendall, 1894 1940 Ladd,1951 1951-58 Parker, 1959 1959-60 Shidler, 1960 1967 Zimmerman and Chaney, 1969 1968 Zimmerman and Chaney, 1969 1971-73 Harper, 1973a, 1973b; Hildebrand and King, 1973 1973-74 Hildebrand and King, 1974; Holland et al., 1974 1974-75 Hildebrand and King, 1975; Rickner, 1975 1975-76 Hildebrand and King, 1976; Calnan, 1980 1976-77 Hildebrand and King, 1977; Circe, 1979; White et al., 1985, 1986a, 1986b, 1987, 1989a, 1989b 1977-78 Hildebrand and King, 1979; Rickner, 1979; Williamson, 1980; Brock, 1983 1980 Wilhite et al., 1982 1981-82 Powell et al., 1982; Castiglione, 1983 1984 Smith, 1985 1986-87 Chaney, 1988; Drumright, 1989 1989-90 Ruth, 1991; Hicks, 1993; Hicks et al., 1998 1992-93 Montagna, 1993; Martin, 1994; Montagna and Martin, 1994 2001-02 Davidson, 2002; Pearce, 2003 2004 Withers, K, pers. observ. 2005 Withers, K, pers. observ.; Hicks, D. W., Univ. Texas-Brownsville, pers. common. 2006 Hubner, 2007 (1) Scallops were freshly dead with tissues still attached. Bay abbreviations: SL = Sabine Lake GB = Galveston Bay system, including Trinity Bay MB = Matagorda Bay system, including Lavaca Bay ES = Espiritu Santo Bay SA = San Antonio Bay system, including Hynes and Mesquite bays AB = Aransas Bay, including St. Charles Bay CB = Copano Bay; RB = Redfish Bay CC = Corpus Christi Bay, including Oso Bay NB = Nueces Bay ULM = Upper Laguna Madre LLM = Lower Laguna Madre, including South Bay Abundance rankings use the author's terminology or were determined as follows: D = dead only P = present in a species checklist, but no abundance data provided 0 = none collected R = rare: less than 5% of total collection. F = few: 6-10% of collection C = common: 15-40% of collection or 40-50% of sites A = abundant:41-60% of collection or 5l-75% of sites VA = very abundant: numerically dominant and present in most sites sampled Table 3.--Total numbers of bay scallops collected in bag seines 1982- 2005. Data provided by Texas Parks and Wildlife Department. San Corpus Upper Lower Matagorda Antonio Aransas Christi Laguna Laguna Year Bay Bay Bay Bay Madre Madre 1982 1983 1984 1985 3 1986 1987 1988 2 8 1989 4 1 1 1990 4 3 1 1991 1 2 3 1992 1993 1 1994 1995 1 3 1996 1 5 2 5 1997 1 1 2 1998 1 1999 2000 1 2 2001 1 2002 2003 2004 1 2005 6 1 Total 2 16 6 21 18 5 Table 4.--Total numbers of scallops collected in trawls 1982-2005. Data provided by Texas Parks and Wildlife Department. San Corpus Upper Lower Matagorda Antonio Aransas Christi Laguna Laguna Year Bay Bay Bay Bay Madre Madre 1982 10 1983 25 1984 12 1985 9 1986 10 1987 385 9 1988 3 7 395 7 1989 1 6 4 2 8 1990 1 1 1 8 1991 2 1992 33 1993 1 1994 1 1995 10 1996 1 1997 1 2 1998 1 4 1 1999 1 9 2000 1 58 2001 5 5 2002 1 2 2003 26 3 2004 938 16 2005 3 1 Total 6 11 7 9 1,822 175 Table 5.--Average length (mm) of bay scallops collected in bag seines 1982-2005 with standard deviation in parenthesis (when more than 1 bay scallop was collected or measured). Data provided by Texas Parks and Wildlife Department. Asterisk (*) indicates that scallops were collected but not measured. Matagorda San Antonio Aransas Year Bay Bay Bay 1982 1983 1984 1985 1986 1987 1988 1989 43.3 (16.9) 50.0 1990 47.8 (22.6) 1991 14.0 1992 1993 1994 1995 11.0 1996 26.0 38.5 (12.2) 29.0 1997 39.0 7.0 40.5 1998 1999 2000 2001 38.0 2002 2003 2004 2005 Overall 32.5 (9.2) 35.9 (19.5) 39.4 (8.6) Corpus Christi Upper Laguna Lower Laguna Year Bay Madre Madre 1982 1983 1984 * 1985 1986 1987 1988 46.0 (1.4) 31.9 (9.3) 1989 35.0 1990 46.7 (9.1) 36.0 1991 57.5 (0.7) 34.8 (2.5) 1992 1993 35.0 1994 1995 42.5 (12.0) 1996 40.8 (21.4) 1997 1998 38.0 1999 2000 32.0 51.0 (9.9) 2001 2002 2003 17 2004 23.8 (8.4) 2005 21 Overall 43.4 (13.4) 27.9 (9.3) 42.9 (11.1) Table 6.--Average length (mm) of bay scallops collected in trawls 1982-2005 with standard deviation in parentheses (when more than 1 bay scallop was collected or measured). Data provided by Texas Parks and Wildlife Department. Asterisk (*) indicates that scallops were collected but not measured. Matagorda San Antonio Aransas Year Bay Bay Bay 1982 1983 1984 1985 1986 1987 1988 32.3 1989 8.0 44.0 (1.4) 47.5 (10.2) 1990 57.0 40.0 1991 1992 1993 1994 1995 1996 1997 22.0 1998 28.0 1999 2000 2001 * 2002 45.0 2003 2004 2005 Overall 39.9 (13.3) 43.3 (10.3) Corpus Christi Upper Laguna Lower Laguna Year Bay Madre Madre 1982 1983 22.4 (11.2) 1984 20.2 (1.0) 1985 21.3 (15.9) 1986 19.0 (8.8) 1987 25.9 (17.6) 37.1 (16.8) 1988 30.2 (6.5) 29.0 (13.4) 23.1 (3.5) 1989 25.5 (14.8) 32.2 (26.8) 1990 26 18.3 (6.3) 1991 18.0 1992 23.3 (6.3) 1993 15.0 1994 26.0 1995 18.1 (6.6) 1996 29.0 1997 29.5 (2.1) 1998 18.5 35.0 1999 27.0 22.5 (10.4) 2000 10.0 21.2 (0.22) 2001 23.3 (13.1) 2002 39.0 (21.2) 2003 20.8 (9.9) 23.3 (2.5) 2004 18.4 (13.4) 25.7 (10.1) 2005 14.70 25.0 Overall 29.9 (4.7) 23.5 (14.1) 25.5 (13.3) Table 7.--Seagrass cover in the northwestern Gulf of Mexico. State Year Area (ha) Trends Alabama (Mobile Bay area) 2002 349 [down arrow] 55-88 % Mississippi (Gulf Islands National Seashore) 1992 140 [down arrow] 66% Lousiana (Chandeleur Islands) 1989 5,657 [down arrow] 12% Texas (entire coast) 1994 ~94409 Galveston Bay system 113 [down arrow] 90+% Matagorda Bay system 1,551 Unknown San Antonio Bay system 4,293 Fluctuates Aransas Bay system 3,240 Unknown Corpus Christi Bay system (including Redfish Bay) 9,963 Stable Laguna Madre system 75,409 Slight decrease State Source Alabama (Mobile Bay area) Barry Vittor and Associates, Inc., 2005 Mississippi (Gulf Islands National Seashore) Handley, 1995 Lousiana (Chandeleur Islands) Handley, 1995 Texas (entire coast) Pulich, 1999 Galveston Bay system Matagorda Bay system San Antonio Bay system Aransas Bay system Corpus Christi Bay system (including Redfish Bay) Laguna Madre system (1) Includes all submerged aquatic vegetation; seagrasses were not separable, but they represented only a small percentage of all submerged vegetation mapped in the study (Barry Vittor and Associates, Inc. 2005)
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