... Patricia Sánchez-Gil a , Corresponding Author Contact Information , E-mail The Corresponding ... more ... Patricia Sánchez-Gil a , Corresponding Author Contact Information , E-mail The Corresponding Author , Alejandro Yáñez-Arancibia b , E-mail The Corresponding Author , Margarito Tapia a , E-mail The Corresponding Author , John W. Day c , E-mail The Corresponding Author ...
Eos, Transactions American Geophysical Union, 2010
Coastal water hypoxia, where dissolved oxygen is less than 2 milligrams per liter, is a global en... more Coastal water hypoxia, where dissolved oxygen is less than 2 milligrams per liter, is a global environmental problem [e.g., Diaz and Rosenberg, 2008]. It is largely associated with eutrophication, whereby nutrient inputs (nitrogen and phosphorous) to coastal waters lead to elevated primary production and accelerated rates of microbial respiration, which results in oxygen depletion. Despite more than 25 years of monitoring [Rabalais et al., 2007] (see also Figure S1 in the online supplement to this Eos issue (http://www.agu.org/eos_elec/)), the relative importance of the various processes that control hypoxia in bottom waters of the northern Gulf of Mexico (GOM)—in particular, those beyond the direct influence of river plumes [Dagg et al., 2007; Bianchi et al., 2008, 2010, and references therein]—remains uncertain. For example, a prediction last June pronounced that the 2009 hypoxic area would be the largest on record (˜23,000 square kilometers; see http://www.gulfhypoxia.net/Research/Shelfwide%20Cruises/2009/Files/2009_Hypoxia_Forecast.pdf). However, the most recent annual surveys estimated its size at 8000 square kilometers, only 35% of that predicted. This occurred in the absence of a significant hurricane impact on this margin in 2009—hurricanes tend to dissipate hypoxia.
Production of bay anchovy Anchoa mitchilli is highest in the larval and juvenile stages. The inte... more Production of bay anchovy Anchoa mitchilli is highest in the larval and juvenile stages. The interplay between vital rates, stage durations, prey resources, and anchovy abundance ultimately determines the relative magnitude of recruitment (which in the model varies by about three-fold) and of stage-specific production. Changes in adult seasonal spawning patterns that increase the number of larval survivors result in only a slight increase in overall production due to density-dependent decreases in growth rates of later life stages. Bay anchovy in the mid-Chesapeake Bay may reach a compensatory threshold during late summer-autumn as fish growth is affected by competition for food resources. Density dependence in the population is evident in the relationships between spawner-recruit, size-recruit, and production of larval or juvenile to young-of-the-year life stages. Density-dependent growth acts differentially upon the early life stage that exceeds the compensatory threshold in any given year, due either to environmental variability or population size, or both. This could explain partially the relatively low recruitment variability observed for this anchovy.
Vol. 185: 133-146.1999 MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Published August 20 ... J... more Vol. 185: 133-146.1999 MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Published August 20 ... James H. Cowan Jr'l*, Kenneth A. ~ ose ~ , ... Edward D. Houde3, Shyh-Bin Wangl, John Young4 ... 'University of South Alabama, Dauphin Island Sea Lab, 101 ...
Ovaries of red snapper Lutjanus campechanus were examined histologically to determine rates of oo... more Ovaries of red snapper Lutjanus campechanus were examined histologically to determine rates of oocyte maturation, diel spawning periodicity and whether lunar cycle influenced spawning rhythm. Hydration of red snapper oocytes began during the mid-morning hours; c. 5 h was necessary for oocytes to become fully hydrated and ovulation occurred no more than 5 h after oocytes attained full hydration. Appearance of fresh postovulatory follicles after 1330 hours and the absence of hydrated oocytes after 1830 hours signified that red snapper spawning occurred during this 5 h period. In addition, evidence of a peak in spawning was seen near 1600 hours. Postovulatory follicles degenerated within a 24 h time period. A lunar spawning cycle was not evident.
Journal of Experimental Marine Biology and Ecology, 2010
Water control structures (WCSs) installed to regulate water levels can alter both the hydrology a... more Water control structures (WCSs) installed to regulate water levels can alter both the hydrology and ecology of salt marshes. WCSs are thought to limit nekton ingress into, and egress from, managed marshes. Slots (vertical openings that span most of the water column) incorporated into WCSs are thought to facilitate nekton passage through structures, but little research has directly examined how slot size affects passage rates. We used dual-frequency identification sonar (DIDSON) acoustic imaging to examine the effect of slot width (10, 15, 30, or 60 cm), tidal cycle, diel period, and season on nekton passage at a WCS located in a tidal salt marsh canal. Few individuals (total numbers and relative percentages) used the slots for passage through the structure during any stage of the tidal cycle, day or night, or seasonally. The number and size of migrants were similar for all four slot sizes examined. Nekton used the slots most often on flood tides to access the managed marsh (i.e., swim inside), primarily at night. Individuals entering the managed marsh were larger than those observed leaving the managed marsh. Whereas the majority of migrants were observed during winter months, season did not affect nekton passage in our study. Acoustic imaging allowed a unique and comprehensive evaluation of nekton passage by permitting an examination of factors such as swimming direction and proportion of migrants that are unobservable with other sampling techniques.
The ability to estimate fish abundance accurately over a particular habitat is contingent upon th... more The ability to estimate fish abundance accurately over a particular habitat is contingent upon the use of appropriate sampling methods. The objectives of this study were to compare the catch per unit area (A), length-specific bias, and relative catchability (q-ratio) of four different gear types for sampling red snapper (Lutjanus campechanus) over natural low-relief reef habitats on the inner continental shelf of the northern Gulf of Mexico. Specifically, our goal was to assess the overall performance of a standard otter trawl, a small fish trap, a chevron trap, and a stationary 4-camera underwater video array during six quarterly sampling cruises performed in 2004 and 2005. The sizes of snapper captured by trawls ranged from 30 to 250 mm total length (TL) (ages 0 and 1 yr). Trawls captured the most red snapper per unit area and had q-ratios of 3:1 to 5:1 relative to small fish traps for juvenile red snapper. The chevron trap collected the second highest number of red snapper and proved most useful at collecting red snapper from 150 to 440 mm TL (ages 1–5 yr). The q-ratio of the chevron trap relative to the underwater video array was approximately 3:1. Our comparison demonstrated the chevron trap is most effective for sampling adults, while trawls were the most effective gear for sampling age-0 yr fish.
Differences in the biological and ecological strategies of two tropical flatfishes, Etropus cross... more Differences in the biological and ecological strategies of two tropical flatfishes, Etropus crossotus (fringed flounder) and Citharichthys spilopterus (bay whiff) are discussed. The comparative analysis was based on the seasonal distribution of relative abundance of the two species and flatfish movements utilizing estuarine plume influenced areas as part of their life cycles. Growth parameters of the von Bertalanffy equation and recruitment were estimated (FISAT software) to compare life cycle patterns. The recruitment patterns illustrate the key difference between “estuarine-dependent” and “estuarine-related” nekton strategies. Both species have a short life cycle with a continuous recruitment activity. E. crossotus is an estuarine-related species, with two recruitment pulses (winter frontal season), in the estuarine plume on the shelf. C. spilopterus is an estuarine-dependent species, with a main recruitment pulse during the rainy season in the estuarine plume, and a residual secondary pulse inside the adjacent estuarine system (Terminos Lagoon). The results show that the ecological success of these tropical coastal marine flatfish, with similar biological patterns, is based upon the sequential use (in time and space) of estuarine plume influenced habitats, suggesting that fish migration to shallow waters is related to food availability changes as a strategy towards optimum recruitment.
... Patricia Sánchez-Gil a , Corresponding Author Contact Information , E-mail The Corresponding ... more ... Patricia Sánchez-Gil a , Corresponding Author Contact Information , E-mail The Corresponding Author , Alejandro Yáñez-Arancibia b , E-mail The Corresponding Author , Margarito Tapia a , E-mail The Corresponding Author , John W. Day c , E-mail The Corresponding Author ...
Eos, Transactions American Geophysical Union, 2010
Coastal water hypoxia, where dissolved oxygen is less than 2 milligrams per liter, is a global en... more Coastal water hypoxia, where dissolved oxygen is less than 2 milligrams per liter, is a global environmental problem [e.g., Diaz and Rosenberg, 2008]. It is largely associated with eutrophication, whereby nutrient inputs (nitrogen and phosphorous) to coastal waters lead to elevated primary production and accelerated rates of microbial respiration, which results in oxygen depletion. Despite more than 25 years of monitoring [Rabalais et al., 2007] (see also Figure S1 in the online supplement to this Eos issue (http://www.agu.org/eos_elec/)), the relative importance of the various processes that control hypoxia in bottom waters of the northern Gulf of Mexico (GOM)—in particular, those beyond the direct influence of river plumes [Dagg et al., 2007; Bianchi et al., 2008, 2010, and references therein]—remains uncertain. For example, a prediction last June pronounced that the 2009 hypoxic area would be the largest on record (˜23,000 square kilometers; see http://www.gulfhypoxia.net/Research/Shelfwide%20Cruises/2009/Files/2009_Hypoxia_Forecast.pdf). However, the most recent annual surveys estimated its size at 8000 square kilometers, only 35% of that predicted. This occurred in the absence of a significant hurricane impact on this margin in 2009—hurricanes tend to dissipate hypoxia.
Production of bay anchovy Anchoa mitchilli is highest in the larval and juvenile stages. The inte... more Production of bay anchovy Anchoa mitchilli is highest in the larval and juvenile stages. The interplay between vital rates, stage durations, prey resources, and anchovy abundance ultimately determines the relative magnitude of recruitment (which in the model varies by about three-fold) and of stage-specific production. Changes in adult seasonal spawning patterns that increase the number of larval survivors result in only a slight increase in overall production due to density-dependent decreases in growth rates of later life stages. Bay anchovy in the mid-Chesapeake Bay may reach a compensatory threshold during late summer-autumn as fish growth is affected by competition for food resources. Density dependence in the population is evident in the relationships between spawner-recruit, size-recruit, and production of larval or juvenile to young-of-the-year life stages. Density-dependent growth acts differentially upon the early life stage that exceeds the compensatory threshold in any given year, due either to environmental variability or population size, or both. This could explain partially the relatively low recruitment variability observed for this anchovy.
Vol. 185: 133-146.1999 MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Published August 20 ... J... more Vol. 185: 133-146.1999 MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Published August 20 ... James H. Cowan Jr'l*, Kenneth A. ~ ose ~ , ... Edward D. Houde3, Shyh-Bin Wangl, John Young4 ... 'University of South Alabama, Dauphin Island Sea Lab, 101 ...
Ovaries of red snapper Lutjanus campechanus were examined histologically to determine rates of oo... more Ovaries of red snapper Lutjanus campechanus were examined histologically to determine rates of oocyte maturation, diel spawning periodicity and whether lunar cycle influenced spawning rhythm. Hydration of red snapper oocytes began during the mid-morning hours; c. 5 h was necessary for oocytes to become fully hydrated and ovulation occurred no more than 5 h after oocytes attained full hydration. Appearance of fresh postovulatory follicles after 1330 hours and the absence of hydrated oocytes after 1830 hours signified that red snapper spawning occurred during this 5 h period. In addition, evidence of a peak in spawning was seen near 1600 hours. Postovulatory follicles degenerated within a 24 h time period. A lunar spawning cycle was not evident.
Journal of Experimental Marine Biology and Ecology, 2010
Water control structures (WCSs) installed to regulate water levels can alter both the hydrology a... more Water control structures (WCSs) installed to regulate water levels can alter both the hydrology and ecology of salt marshes. WCSs are thought to limit nekton ingress into, and egress from, managed marshes. Slots (vertical openings that span most of the water column) incorporated into WCSs are thought to facilitate nekton passage through structures, but little research has directly examined how slot size affects passage rates. We used dual-frequency identification sonar (DIDSON) acoustic imaging to examine the effect of slot width (10, 15, 30, or 60 cm), tidal cycle, diel period, and season on nekton passage at a WCS located in a tidal salt marsh canal. Few individuals (total numbers and relative percentages) used the slots for passage through the structure during any stage of the tidal cycle, day or night, or seasonally. The number and size of migrants were similar for all four slot sizes examined. Nekton used the slots most often on flood tides to access the managed marsh (i.e., swim inside), primarily at night. Individuals entering the managed marsh were larger than those observed leaving the managed marsh. Whereas the majority of migrants were observed during winter months, season did not affect nekton passage in our study. Acoustic imaging allowed a unique and comprehensive evaluation of nekton passage by permitting an examination of factors such as swimming direction and proportion of migrants that are unobservable with other sampling techniques.
The ability to estimate fish abundance accurately over a particular habitat is contingent upon th... more The ability to estimate fish abundance accurately over a particular habitat is contingent upon the use of appropriate sampling methods. The objectives of this study were to compare the catch per unit area (A), length-specific bias, and relative catchability (q-ratio) of four different gear types for sampling red snapper (Lutjanus campechanus) over natural low-relief reef habitats on the inner continental shelf of the northern Gulf of Mexico. Specifically, our goal was to assess the overall performance of a standard otter trawl, a small fish trap, a chevron trap, and a stationary 4-camera underwater video array during six quarterly sampling cruises performed in 2004 and 2005. The sizes of snapper captured by trawls ranged from 30 to 250 mm total length (TL) (ages 0 and 1 yr). Trawls captured the most red snapper per unit area and had q-ratios of 3:1 to 5:1 relative to small fish traps for juvenile red snapper. The chevron trap collected the second highest number of red snapper and proved most useful at collecting red snapper from 150 to 440 mm TL (ages 1–5 yr). The q-ratio of the chevron trap relative to the underwater video array was approximately 3:1. Our comparison demonstrated the chevron trap is most effective for sampling adults, while trawls were the most effective gear for sampling age-0 yr fish.
Differences in the biological and ecological strategies of two tropical flatfishes, Etropus cross... more Differences in the biological and ecological strategies of two tropical flatfishes, Etropus crossotus (fringed flounder) and Citharichthys spilopterus (bay whiff) are discussed. The comparative analysis was based on the seasonal distribution of relative abundance of the two species and flatfish movements utilizing estuarine plume influenced areas as part of their life cycles. Growth parameters of the von Bertalanffy equation and recruitment were estimated (FISAT software) to compare life cycle patterns. The recruitment patterns illustrate the key difference between “estuarine-dependent” and “estuarine-related” nekton strategies. Both species have a short life cycle with a continuous recruitment activity. E. crossotus is an estuarine-related species, with two recruitment pulses (winter frontal season), in the estuarine plume on the shelf. C. spilopterus is an estuarine-dependent species, with a main recruitment pulse during the rainy season in the estuarine plume, and a residual secondary pulse inside the adjacent estuarine system (Terminos Lagoon). The results show that the ecological success of these tropical coastal marine flatfish, with similar biological patterns, is based upon the sequential use (in time and space) of estuarine plume influenced habitats, suggesting that fish migration to shallow waters is related to food availability changes as a strategy towards optimum recruitment.
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