David L. Jones

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.

Preliminary classification of the gurnards (Triglidae: Scorpaeniformes)

The triglid fishes, commonly known as gurnards or searobins, are found in tropical and temperate waters of the world’s oceans. This preliminary classification recognizes 8 genera and ~125 species, of which ~15 species are undescribed. This classification is based on 11 morphological characters, most of which are osteological. The tribes and genera are as follows. Prionotini (Prionotus and Bellator) is the most primitive: 26 vertebrae, lateral line ending at caudal base and not bifurcate on caudal fin, basihyal present, and no expansion of distal part of the proximal pterygiophores. Pterygotriglini (Bovitrigla, Pterygotrigla, and Uradia): 27 vertebrae, lateral line ending at caudal base and not bifurcate on caudal fin, basihyal absent, and no expansion of distal end of the proximal pterygiophores or expansion of only those next to the first dorsal fin. Triglini (Trigla, Chelidonichthys and Lepidotrigla): all the distal ends of the proximal pterygiophores expanded and exposed along the first and second dorsal fin bases, basihyal absent, lateral line bifurcate on caudal fin, and 29–35 vertebrae. Examples of the characters are discussed in relation to the difficulties in assigning character states in light of reversals and multiple reversals.

Distribution of gymnosomatous pteropods in western Antarctic Peninsula shelf waters: influences of Southern Ocean water masses

Distributions of gymnosomatous pteropods, Spongiobranchaea australis and Clione antarctica , were determined at six sites along a latitudinal gradient in western Antarctica Peninsula shelf waters using vertically stratified trawls. Hydrographic data were collected at the same sites with conductivity-temperature-depth casts, and correlations of explanatory variables to gymnosome distributions were determined using statistical analyses performed in Matlab, a high level programming software to conduct numerical computation and visualisation. Explanatory variables included sampling site, latitude, longitude and depth, seawater temperature, salinity and density, Southern Ocean Antarctic Surface Water, Winter Water, Upper Circumpolar Deep Water and warm transitional waters, as well as oceanographic remote sensing data for coloured dissolved organic matter, chlorophyll a concentration, normalised fluorescence line height, nighttime sea surface temperature, photosynthetically active radiation, particulate inorganic carbon, particulate organic carbon, daytime sea surface temperature and daily sea ice concentration. Hydrographic data revealed that warmer water masses were prevalent along the western Antarctic Peninsula, and the distributions of both gymnosome species were primarily influenced by water masses, temperature, sampling site and latitude. As a consequence, distributional shifts of gymnosomes are predicted in response to the current warming trends.

Associations between metal exposure and lesion formation in offshore Gulf of Mexico fishes collected after the Deepwater Horizon oil spill

The objectives of this study were to: (1) examine patterns of short- and long-term metal exposure within the otoliths of six offshore fish species in varying states of health, as indicated by the presence of external skin lesions, and (2) determine if there was a change in otolith metal concentrations concurrent with the Deepwater Horizon (DWH) oil spill. Otoliths collected from 2011 to 2013 in the Gulf of Mexico (GOM) were analyzed for a suite of trace metals known to be associated with DWH oil. We found that lesioned fish often had elevated levels of otolith 60Ni and 64Zn before, during, and after the DWH oil spill. In addition, metal exposure varied according to species-specific life history patterns. These findings indicate that lesioned individuals were exposed to a persistent source of trace-metals in the GoM prior to the oil spill.

Strategic assessment of fisheries independent monitoring programs in the Gulf of Mexico

This study evaluates information produced from 14 fisheries independent monitoring programs (FIM) in the Gulf of Mexico. We consider the uniqueness of information from each program and its usefulness in estimating fisheries management indices. Biomass values of 35 functional groups are extracted from an operating model (Ecospace) with a method that replicates the patterns of historic FIM samplings. Observation error is added to these data in order to create a set of pseudo data that replicate the type and quality of information obtained from FIM programs. The pseudo data were put into a separate fishery assessment model (Pella-Tomlinson) to determine management indices of each functional group (maximum sustainable yield (MSY), biomass at MSY, and fishing mortality at MSY). These indices are compared against values in Ecospace, and against previously published single-species stock assessments. We also evaluate the full suite of information derived from FIM within an ecosystem context, considering whether functional roles are over- or under-sampled, and whether sampling effort is proportional to the value of fish stocks. Results reveal that model derived fishery indices closely matched published indices for the majority of the functional groups, economic and ecological evaluation suggests that several piscivorous functional groups are under-sampled include forage base species that are likely to indirectly support fisheries for piscivores, and sampling efforts are not proportional to the value of some fish stocks. Following ecological modelling we performed statistical analyses on historic FIM catch data to identify optimal species-specific sampling months and gear-types that can be used to refine future FIM sampling efforts.

The Effects of Spatial Scale on Assigning Nursery Habitats in Atlantic Goliath Groupers (Epinephelus itajara) Using Non-lethal Analyses of Fin Rays

We evaluated Atlantic Goliath Groupers, Epinephelus itajara, in their nursery habitats via microchemical analyses of fin rays. Juveniles were sampled from known nursery habitats off southwest Florida, and adults were primarily sampled from a spawning aggregation off southeast, Florida. We collected fin rays using a non-lethal technique that is minimally invasive with no known negative effects on growth or survival. Trace metal constituents in the fin rays were quantified with an inductively coupled plasma mass spectrometer via laser ablation (LA-ICP-MS). Two spatial scales were quantified to test the limitations of grouping individuals based on elemental compositions. On a small spatial scale (i.e., 100s of m), individuals were correctly classified within individual watersheds 64% of the time. On a larger spatial scale (i.e., 10s–100s of km), juveniles were classified with 100% accuracy. Trace metals in adults were analyzed by back-tracking across fin ray annuli to a year in which our previous studies have shown these adults occupied their juvenile habitats (i.e., 2006). These fish were grouped using a measure of dissimilarity and then analyzed to test whether we could reclassify them into these same groupings based solely on the chemical components in their fin rays, which was done with over 84% accuracy. Although juvenile habitats of the adults could not be determined due to the lack of baseline data, classifications were driven by similar elements to those that drove the classification of juveniles, suggesting similar physiological mechanisms. The results highlight the importance of spatial scale for interpreting microchemical analyses on calcified structures in fishes.

Resemblance profiles as clustering decision criteria: Estimating statistical power, error, and correspondence for a hypothesis test for multivariate structure

Abstract Clustering data continues to be a highly active area of data analysis, and resemblance profiles are being incorporated into ecological methodologies as a hypothesis testing‐based approach to clustering multivariate data. However, these new clustering techniques have not been rigorously tested to determine the performance variability based on the algorithms assumptions or any underlying data structures. Here, we use simulation studies to estimate the statistical error rates for the hypothesis test for multivariate structure based on dissimilarity profiles (DISPROF). We concurrently tested a widely used algorithm that employs the unweighted pair group method with arithmetic mean (UPGMA) to estimate the proficiency of clustering with DISPROF as a decision criterion. We simulated unstructured multivariate data from different probability distributions with increasing numbers of objects and descriptors, and grouped data with increasing overlap, overdispersion for ecological data, and correlation among descriptors within groups. Using simulated data, we measured the resolution and correspondence of clustering solutions achieved by DISPROF with UPGMA against the reference grouping partitions used to simulate the structured test datasets. Our results highlight the dynamic interactions between dataset dimensionality, group overlap, and the properties of the descriptors within a group (i.e., overdispersion or correlation structure) that are relevant to resemblance profiles as a clustering criterion for multivariate data. These methods are particularly useful for multivariate ecological datasets that benefit from distance‐based statistical analyses. We propose guidelines for using DISPROF as a clustering decision tool that will help future users avoid potential pitfalls during the application of methods and the interpretation of results.