Maria M. Criales

Dynamics of pink shrimp (Farfantepenaeus duorarum) recruitment potential in relation to salinity and temperature in Florida Bay

Progress is reported in relating upstream water management and freshwater flow to Florida Bay to a valuable commercial fishery for pink shrimp (Farfantepenaeus duorarum), which has major nursery grounds in Florida Bay. Changes in freshwater inflow are expected to affect salinity patterns in the bay, so the effect of salinity and temperature on the growth, survival, and subsequent recruitment and harvest of this ecologically and economically important species was examined with laboratory experiments and a simulation model. Experiments were conducted to determine the response of juvenile growth and survival to temperature (15°C to 33°C) and salinity (2‰ to 55‰), and results were used to refine an existing model. Results of these experiments indicated that juvenile pink shrimp have a broad salinity tolerance range at their optimal temperature, but the salinity tolerance range narrows with distance from the optimal temperature range, 20–30°C. Acclimation improved survival at extreme high salinity (55‰), but not at extremely low salinity (i.e., 5‰, 10‰). Growth rate increases with temperature until tolerance is exceeded beyond about 35°C. Growth is optimal in the mid-range of salinity (30‰) and decreases as salinity increases or decreases. Potential recruitment and harvests from regions of Florida bay were simulated based on local observed daily temperature and salinity. The simulations predict that potential harvests might differ among years, seasons, and regions of the bay solely on the basis of observed temperature and salinity. Regional differences in other characteristics, such as seagrass cover and tidal transport, may magnify regional differences in potential harvests. The model predicts higher catch rates in the September–December fishery, originating from the April and July settlement cohorts, than in the January–June fishery, originating from the October and January settlement cohorts. The observed density of juveniles in western Florida Bay during the same years simulated by the model was greater in the fall than the spring, supporting modeling results. The observed catch rate in the fishery, a rough index of abundance, was higher in the January–June fishery than the July–December fishery in most of the biological years from 1989–1990 through 1997–1998, contrary to modeling results and observed juvenile density in western Florida Bay.

Influence of coastal eddies and counter-currents on the influx of spiny lobster, Panulirus argus , postlarvae into Florida Bay

Postlarvae of the spiny lobster Panulirus argus migrate from offshore in the Florida Keys into their juvenile habitat in Florida Bay through interisland channels. The influx of postlarvae was monitored monthly over the new-moon period at Long Key and Whale Harbor channels (July 1997-June 1999). Although the channels were only 30 km apart, their influx patterns differed. At Long Key, influx peaked every 2-3 months, whereas at Whale Harbor the peaks were in winter and of higher magnitudes. The influx pattern at Long Key was highly correlated with the strength of coastal counter-current flow in the two-week period prior to sampling. Counter- current flow was correlated with alongshore (upstream) wind stress, but the latter was not a significant predictor of postlarval influx. Coastal counter-current flow is hypothesized to indicate the presence of a cyclonic, mesoscale eddy offshore. Satellite imagery confirmed the presence of these eddies offshore of the Middle Florida Keys often when positive postlarval influx and counter-current anomalies were observed. These eddies can facilitate onshore larval transport, and their variable temporal and spatial properties can cause transport variability over a scale of several tens of kilometres along the Keys.

Variation of oceanographic processes affecting the size of pink shrimp (Farfantepenaeus duorarum) postlarvae and their supply to Florida Bay

Abstract Pink shrimp ( Farfantepenaeus duorarum ) postlarvae were collected monthly with moored channel nets from October 1997 to June 1999 at Whale Harbor (WH) and Long Key (LK) Channels, two channels at the east and west ends of the Middle Florida Keys that connect the Atlantic Ocean with Florida Bay, the main nursery ground of this species in south Florida. The density influx of pink shrimp postlarvae through these two channels differed in magnitude and seasonal patterns. The monthly influx of postlarvae at LK was lower in magnitude but steadier than at WH. LK showed the highest postlarval influx in late spring–summer. Postlarval influx through WH further downstream showed both spring–summer and winter peaks. The spring–summer peaks correspond with favorable wind and current conditions. In contrast, the winter peaks occurred when cyclonic eddies were detected passing through the Middle Florida Keys. These cyclonic eddies induced coastal countercurrent flow that favors onshore larval transport. The position of the leading edge of the eddy relative to the channels may cause the temporal variability observed in the temporal postlarval influx patterns between channels. A seasonal size variation in postlarvae was also observed at both sampling sites. Postlarvae captured during the winter months were significantly larger than those captured during the summer months. The number of rostral spines, a morphological feature generally correlating with the number of moults and age, also varied seasonally but with a trend opposite to that of the body size, which may indicate a lengthening of the intermoult period during wintertime. The reasons for the seasonal differences in growth rates and, possibly, different lengths of time in the currents, are yet to be resolved.

MICROPROSTHEMA GRANATENSE, NEW SPECIES, FROM THE SOUTHERN CARIBBEAN, WITH A KEY TO SHRIMPS OF THE GENUS MICROPROSTHEMA FROM THE WESTERN ATLANTIC AND A NEW RECORD OF ODONTOZONA LIBERTAE (DECAPODA: STENOPODIDEA)

ABSTRACT The shrimp Microprosthema granatense, new species, is described and illustrated from material collected in Granate Bay, Caribbean coast of Colombia. This male shrimp was collected together with 3 ovigerous females of the stenopodidean Odontozona libertae Gore around the talus pile of the burrow of a tilefish. Microprosthema granatense differs from other species of Microprosthema mainly by having few spinous processes and spines on the carapace, a larger cornea, different spination of the third maxilliped and third pereiopod, and very long and multisegmented fourth and fifth pereiopods. Comparisons with other species of the genus are made and a key for the species of Microprosthema of the western Atlantic is provided. The record of Odontozona libertae constitutes the first for the southern Caribbean.

Field Observations on Selective Tidal-Stream Transport for Postlarval and Juvenile Pink Shrimp in Florida Bay

Abstract Postlarvae and juveniles of pink shrimp were collected in the summers of 2005 and 2006 at three stations in northwestern Florida Bay, the main nursery ground of this species in South Florida. Collections were made at one- or two-hour intervals during three full moon nights and two new moon nights at depth intervals in the water column. Results of the five collections were consistent with the assumption that postlarvae use a flood-tide transport (FTT) to advance into the estuary by ascending in the water column during the dark-flood tide and resting near the bottom during the ebb tide. Evidence of a FTT were higher numbers of postlarvae per hour collected during the flood tide vs. ebb tide and the large number of postlarvae collected with highest velocity flood tide currents. ANOVA indicated significant differences in the number of postlarvae collected between tidal stages and moon phases, but not among depths. Postlarvae were more abundant during new moon than full moon. We also found different patterns of postlarval distribution between the new and full moon. During the new moon, a large peak of postlarvae occurred coincident with highest current speeds, whereas, with one exception, during the full moon postlarvae were more abundant in the second half of the flood period near the slack tide. In contrast, juveniles exhibited a behavior and migratory pattern opposite to that of postlarvae. ANOVA indicated significant differences between the number of juveniles captured between tidal stages and among depths, but not between moon phases. Juveniles were found almost exclusively near the surface on the ebb tide. Significantly larger juveniles were captured on the dark-ebb rather than on the dark-flood tide during both moon phases, suggesting that older juveniles were leaving the Bay on the ebb tide.

Modeling Larval Transport and Settlement of Pink Shrimp in South Florida: Dynamics of Behavior and Tides

Abstract The pink shrimp Farfantepenaeus duorarum, one of the commercially important Penaeidae, reproduces offshore of the southwest Florida (SWF) shelf. Larvae migrate to nursery grounds in estuarine Florida Bay. Using a numerical approach, we investigated the role of spawning location, larval traits, and physical forces on the transport of pink shrimp larvae. First, the Regional Oceanic Modeling System that is based on tides, air—ocean fluxes, and freshwater flows was used to simulate the SWF shelf oceanography. The model replicates the tides, winds, salinity, currents, and seasonality of the shelf. Secondly, the Regional Oceanic Modeling System was coupled offline with the Connectivity Modeling System, in which virtual larvae were released near the surface from two spawning sites, Dry Tortugas and Marquesas, and tracked until the time for settlement (about 28–30 d). Virtual larvae moved vertically in the water column following ontogenetic behaviors previously observed in the field: diel vertical migration (DVM) and selective tidal stream transport (STST). Lagrangian trajectories indicated that migration paths changed radically between summer and winter during model years (1995–1997). Maximum settlements occurred in summer by larvae crossing the SWF shelf, while the lowest settlement occurred in winter by larvae moving through passes in the Florida Keys. Modeling results demonstrated an effective east-northeast transport across the SWF shelf during summer as a result of the tidal currents, the subtidal currents, and the combined DVM and STST behaviors. The current phase captured during the initial DVM period was critical to determine the direction in which larvae move, favorable (east and northward) or unfavorable (south and westward), before the STST behavior captures the eastward tidal current that brings larvae to the nursery grounds. Unfavorable currents were driven by the summer easterlies and low salinities at the coast. Results indicated that Marquesas is the more effective spawning ground, with 4.5 times more likely settlement of originating larvae compared with Dry Tortugas. Model-estimated seasonal settlement patterns concurred with postlarval influxes previously observed at Florida Bay boundaries.

Unusual larval abundance of Scyllarides nodifer and Albunea sp. during an intrusion of low-salinity Mississippi flood water in the Florida Keys in September 1993: Insight into larval transport from upstream

A massive intrusion of low-salinity water (salinity = 31–35) from the Mississippi River to the Florida Keys in September 1993 coincided with an unusual abundance of the phyllosoma larvae (stages IV–VII) of a slipper lobster, Scyllarides nodifer, and the zoeae (stages III–V) of a sand crab, Albunea sp. These species are abundant in the northeastern Gulf of Mexico, but their adults and early stage larvae are not common in the Florida Keys. The influx of S. nodifer and Albunea sp. larvae into the Florida Keys is believed to have originated on the northeastern Gulf of Mexico shelf. The southward transport of the larvae within a low-salinity plume from the Mississippi River was apparently caused by anomalous eastward winds moving shelf waters into the Loop Current, which had extended to within ∼170 km of the Mississippi Delta. During normal-salinity conditions (salinity > 36) the spiny lobster Panulirus argus is the most numerous species of phyllosoma larvae in the coastal waters of the Florida Keys. A wide range of stages of P. argus is present year-round in the Florida Keys, suggesting multiple larval sources upstream possibly in the Yucatan Peninsula and the Caribbean. In contrast, the source of S. nodifer and Albunea sp. recruits for the Florida Keys may lie principally in the northeastern gulf. The recruitment success of larvae of gulf origin to the Florida Keys may depend partly on the coincidence of specific wind and Loop Current transport conditions with an availability of larvae for expatriation at the source.

DIFFERENTIAL USE OF THALASSIA TESTUDINUM HABITATS BY SYMPATRIC PENAEIDS IN A NURSERY GROUND OF THE SOUTHERN GULF OF MEXICO

Density of Penaeidae was assessed in habitats of Thalassia testudinum with different relative location (inshore zone and coastal lagoon) and sediment type (fine sand and coarse sand) during three weather seasons in the Yucatan peninsula, Mexico. A total of 26,847 penaeids were collected on a fortnightly basis from June 2001 to May 2002. A differential habitat use was observed in juveniles of three species of penaeids. Densities of Farfantepenaeus brasiliensis (mean size ± SD: 8.3 ± 3.8 mm CL, carapace length) and Farfantepenaeus notialis (5.5 ± 2.2 mm CL) were highest in the coastal lagoon in T. testudinum on fine sand, while density of Metapenaeopsis goodei (6.7 ± 1.7 mm CL) was also highest in T. testudinum on fine sand, but in the inshore zone. This spatial distribution pattern varied little during the three sampling seasons. A unimodal temporal distribution pattern was observed for juveniles of each species of penaeid, the abundance peaks of F. brasiliensis and M. goodei overlap in the nortes season, while the abundance peak of F. notialis was distinct, peaking in the rainy season. In contrast to juveniles, epibenthic Farfantepenaeus spp. postlarvae (3.2 ± 0.5 mm CL) had a more uniform spatial distribution with a bimodal temporal distribution pattern, a highest abundance peak in the late rainy-early nortes seasons and other minor in the dry season. A redundancy analysis indicated that densities of penaeids were related primarily with water salinity, sediment grain size, and aboveground biomass and structural complexity of T. testudinum, which are variables closely linked with the spatial arrangement of the habitats along the inshore zone and coastal lagoon. The use of different T. testudinum habitats allows coexistence of sympatric penaeids in the nursery ground with minimal inter-specific interactions.

Influence of Temperature and Salinity on Growth, Survival, and Biomass Productivity of Postlarval and Early Juvenile Pink Shrimp Farfantepenaeus duorarum (Burkenroad 1939)

ABSTRACT An investigation was conducted of the combined effect of salinity and temperature on growth, survival, and biomass productivity of postlarval and early juvenile pink shrimp Farfantepenaeus duorarum (Burkenroad 1939) produced from a single spawning event. The study used a factorial block design consisting of three salinity treatments (15, 35, and 55), each replicated, within three temperature treatment (22°C, 27°C, and 32°C) water baths. The study was divided into two phases: postlarval (first 28 days) and early juvenile (second 28 days). Growth was assessed every 7 days throughout the experiment by measuring carapace length (CL) and wet weight (WWT) of 15 randomly selected shrimp from each temperature/salinity replicate tank. After the first study phase, survival was assessed and experimental aquaria were reset with 30 randomly selected shrimp from the same temperature—salinity replicates. Survival was assessed again at the end of the early juvenile phase. The effect of treatments was evaluated by average growth (average finalWWT), survival, and average final biomass production. Exponential growth rates (CL andWWT) and temperature physiological coefficients (Q10) were also computed. Effects of temperature and salinity on growth and survival were variable, and no significant interaction among the treatment factors was observed. Biomass production increased consistently with temperature (postlarval, P > 0.0001; early juvenile, P < 0.0001) and decreased at the highest salinity (55; postlarval, P = 0.0140; early juvenile, P < 0.0001). Significant reductions in all performance outcomes except postlarval growth (P > 0.05) were observed at the high salinity of 55. The response of growth to salinity was not significant until the early juvenile treatment phase, whereas the effect of temperature on growth was significant during both phases. Hypersalinity (salinity, 55) had a detrimental effect on performance outcomes; however, performance outcomes at salinities of 15 and 35 were comparable. These results have implications for the natural productivity of pink shrimp in Florida Bay, where conditions are often hypersaline.