Natural variability and effects of cleaning and storage procedures on vertebral chemistry of the blacktip shark Carcharhinus limbatus.

Key methodological assumptions regarding the degree of natural variability and influence of sample handling and storage of elasmobranch vertebral chemistry were assessed using laser-ablation inductively coupled plasma mass spectrometry. Vertebral chemistry of juvenile blacktip sharks Carcharhinus limbatus was examined to identify whether differences existed among different regions of the vertebral column, between thoracic vertebrae of individual fish or within individual vertebrae. Additionally, the effects of bleach exposure and storage in ethanol on vertebral chemistry were compared. No significant variation in vertebral chemistry was found among different regions of the vertebral column or between thoracic vertebrae, but significant differences among transect locations within individual vertebrae were observed. The variation at all three levels appears comparable with published data on sagittal otoliths of bilaterally symmetrical teleost fishes. The experimental assessment of potential treatment effects indicated vertebral chemistry was not significantly affected by bleach or exposure to ethanol. Taken together, these results support the idea that vertebrae taken from the same region of the vertebral column can be treated as equivalent and at least certain elements remain robust to exposure to bleach and ethanol.

An assessment of the diet and trophic level of Atlantic sharpnose shark Rhizoprionodon terraenovae.

A re-assessment of the diet of the Atlantic sharpnose shark Rhizoprionodon terraenovae was conducted to provide an update on their trophic level. Rhizoprionodon terraenovae primarily consume teleosts, but previously unreported loggerhead sea turtles Caretta caretta were also found in the diet. Analysis suggests that calculated trophic level may depend on diet and geographic area.

Occurrence and habitat use of the critically endangered smalltooth sawfish Pristis pectinata in the Bahamas.

This study documents and discusses recent (2002-2015) sightings and captures of smalltooth sawfish Pristis pectinata in the Bahamas. Movement patterns and habitat preferences of five P. pectinata are examined: two tracked with acoustic telemetry in Bimini and three tagged with pop-up archival transmitting tags in Andros. Historically, P. pectinata may have been distributed throughout the Bahamas; however, since 2002 only 61 encounters were recorded including: Andros (30), Bimini (19) and a handful across other Islands (12). In Bimini, all P. pectinata were >225 cm (stretched total length, LST) suggesting that it is not used as a nursery area. Pristis pectinata in Andros ranged from c. 80 to 450 cm (LST) indicating that this island might be an important nursery and breeding habitat. Pristis pectinata tracked in both islands remained at depths <3 m, often adjacent to mangrove habitats, displaying residency from 42 days (Bimini) to 180 days (Andros). These preliminary findings confirm the Bahamas as an important habitat for P. pectinata and emphasize the urgent need for national protection and management of this population.

Relative abundance and size of coastal sharks derived from commercial shark longline catch and effort data.

In the north-west Atlantic Ocean, stock assessments conducted for some commercially harvested coastal sharks indicate declines from 64 to 80% with respect to virgin population levels. While the status of commercially important species is available, abundance trend information for other coastal shark species in the north-west Atlantic Ocean are unavailable. Using a generalized linear modelling (GLM) approach, a relative abundance index was derived from 1994 to 2009 using observer data collected in a commercial bottom longline fishery. Trends in abundance and average size were estimated for bull shark Carcharhinus leucas, spinner shark Carcharhinus brevipinna, tiger shark Galeocerdo cuvier and lemon shark Negaprion brevirostris. Increases in relative abundance for all shark species ranged from 14% for C. brevipinna, 12% for C. leucas, 6% for N. brevirostris and 3% for G. cuvier. There was no significant change in the size at capture over the time period considered for all species. While the status of shark populations should not be based exclusively on abundance trend information, but ultimately on stock assessment models, results from this study provide some cause for optimism on the status of these coastal shark species.

Habitat use and movement patterns of bull sharks Carcharhinus leucas determined using pop-up satellite archival tags.

Habitat use, movement and residency of bull sharks Carcharhinus leucas were determined using satellite pop-up archival transmitting (PAT) tags throughout coastal areas in the U.S., Gulf of Mexico and waters off the south-east U.S. From 2005 to 2007, 18 fish (mean size = 164 cm fork length, L(F)) were tagged over all seasons. Fish retained tags for up to 85 days (median = 30 days). Based on geolocation data from initial tagging location to pop-off location, C. leucas generally travelled c. 5-6 km day(-1) and travelled an average of 143.6 km. Overall, mean proportions of time at depth revealed C. leucas spent the majority of their time in waters <20 m. They exhibited significant differences among depths but were not found at a particular depth regardless of diurnal period. Most fish occupied temperatures c. 32 degrees C with individuals found mostly between 26 and 33 degrees C. Geolocation data for C. leucas were generally poor and varied considerably but tracks for two individuals revealed long distance movements. One fish travelled from the south-east coast of the U.S. to coastal Texas near Galveston while another moved up the east coast of the U.S. to South Carolina. Data on C. leucas movements indicated that they are found primarily in shallower waters and tend to remain in the same location over long periods. While some individuals made large-scale movements over open ocean areas, the results emphasize the importance of the coastal zone for this species as potential essential habitat, particularly in areas of high freshwater inflow.

Standard oxygen consumption of seasonally acclimatized cownose rays, Rhinoptera bonasus (Mitchill 1815), in the northern Gulf of Mexico.

Standard oxygen consumption rate (MO(2)) was determined for 19 cownose rays (Rhinoptera bonasus) using flow-through respirometry. Rays ranged in size from 0.4 to 8.25 kg (350-790 mm DW). Respirometry experiments were conducted on seasonally acclimatized rays at temperatures from 19.0 to 28.8 degrees C. Estimates of mass-dependent MO(2) ranged from 55.88 mg O(2) kg(-1) h(-1) for an 8.25 kg ray to 332.75 mg O(2) kg(-1) h(-1) for a 2.2 kg animal at 22-25 degrees C. Multiple regression analysis examining the effect of temperature, salinity, and mass on standard mass-independent MO(2) found temperature (P < 0.01), and mass (P < 0.0001) to have a significant effect on oxygen consumption, whereas salinity did not (P > 0.05). Q (10) was calculated as 2.33 (19-28 degrees C), falling between the estimates determined for two other batoid species, the bull ray (Myliobatos aquila; Q (10) = 1.87) and the bat ray (Myliobatis californica; Q (10) = 3.00). The difference in the Q (10) estimates may be attributed to the use of seasonally acclimatized as opposed to laboratory-acclimated animals.

A comparison via simulation of least squares Lehmann-Scheffé estimators of two variances and heritability with those of restricted maximum likelihood.

The objective was to compare the performance of a recently derived, new method of estimating variances and covariances with any mixed linear model and any pattern of missing data with that of restricted maximum likelihood. For each of 96 combinations of six three-herd x four-sire unbalanced designs of 39 offspring each, four heritability values, two ratios of sire variance to interaction variance, and two distributions (multivariate normal and multivariate chi2, 3 df), 15,000 vectors (n = 39) were generated. Least squares Lehmann-Scheffé (LSLS) estimators of sire variance, interaction variance, and heritability were compared to those of REML with the performance measures of percentage of estimates (of the 15,000) that were positive, mean square error, variance, percentage of estimates within +/- 50% of the parameter, bias, maximum value, skewness, and kurtosis. The LSLS method vastly outperformed REML in almost all 96 combinations. Averaged over the 48 combinations with multivariate normal data, the average percentage that REML estimators of heritability performed relative to those of LSLS for the first five of the above listed eight performance measures was -100%. The number of times LSLS was better than REML was 235 out of 240. The analogous values for the 48 combinations with multivariate chi2, 3-df data were -90% and 230 out of 240. The REML maximum values were always larger than the LSLS values. The LSLS skewness and kurtosis values were about the same as those for REML, with the exception of LSLS heritability kurtosis values, which were notably less than those for REML. The explicit expectations of the LSLS estimators showed that the LSLS estimators were surprisingly unbiased given the paucity of data. Explicit coefficients for calculating mean square errors, variances, and biases squared of the LSLS estimators of the three variances were obtained for each design. The LSLS advantage was not quite so large with the multivariate chi2, 3-df data as with the multivariate normal data. Results with a symmetric multinomial distribution were the same as with the multivariate normal. The overall result was that the LSLS estimators produced substantially more non-zero estimates than REML estimators and these more abundant positive estimates were substantially grouped closer to their respective parameters. Results justify efforts to make the LSLS procedure computationally available.

Bioelectrical impedance: fat content of beef and pork from different size grinds.

Multiple linear regression equations were developed for predicting the percentage of fat content of beef and pork. The predictor variables were bioelectrical resistance, temperature, and weight of product. Equations were developed for trim and product ground through a .95- or a .32-cm plate. The trim, .95-cm, and .32-cm grinds had 64, 108, and 96 observations, respectively, for beef product and 56, 101, and 92 observations, respectively, for pork product. Each of these observations was the average of bioelectrical impedance measurements taken in triplicate. The fat percentage ranges were 4 to 50% for beef and 7.5 to 50% for pork. The prediction equation applied to beef trim provided the following values: R2 = .80, Mallows's C(P) = 5.1, and root mean square error = 6.64. The R2 for equations predicting fat percentage in .95- and .32-cm ground beef were .84 and .95, respectively. The prediction equation applied to pork trim provided the following values: R2 = .77, Mallow's C(P) = 5.0, and root mean square error = 6.2. The R2 for equations predicting fat percentage in .95- and .32-cm ground pork were .87 and .96, respectively. The analyses were repeated with data sets of observations with less than 35% fat. The sample sizes and R2 for the trim, .95-, and .32-cm ground beef were 48, .36; 76, .60; and 65, .86; respectively. The sample sizes and R2 for the trim, .95-, and .32-cm ground pork were 42, .64; 62, .66; and 58, .92; respectively. Resistance, temperature, and weight remained as predictor variables for ground product with less than 35% fat. The smaller the grind, the more accurate the prediction. These results are positive for developing inexpensive, on-line systems for efficiently mixing ground product to a specific fat percentage.