Using sea lion-borne video to map diverse benthic habitats in southern Australia

Across the world’s oceans, our knowledge of the habitats on the seabed is limited. Increasingly, video/imagery data from remotely operated underwater vehicles (ROVs) and towed and drop cameras, deployed from vessels, are providing critical new information to map unexplored benthic (seabed) habitats. However, these vessel-based surveys involve considerable time and personnel, are costly, require favorable weather conditions, and are difficult to conduct in remote, offshore, and deep marine habitats, which makes mapping and surveying large areas of the benthos challenging. In this study, we present a novel and efficient method for mapping diverse benthic habitats on the continental shelf, using animal-borne video and movement data from a benthic predator, the Australian sea lion (Neophoca cinerea). Six benthic habitats (between 5-110m depth) were identified from data collected by eight Australian sea lions from two colonies in South Australia. These habitats were macroalgae reef, macroalgae meadow, bare sand, sponge/sand, invertebrate reef and invertebrate boulder habitats. Percent cover of benthic habitats differed on the foraging paths of sea lions from both colonies. The distributions of these benthic habitats were combined with oceanographic data to build Random Forest models for predicting benthic habitats on the continental shelf. Random forest models performed well (validated models had a >98% accuracy), predicting large areas of macroalgae reef, bare sand, sponge/sand and invertebrate reef habitats on the continental shelf in southern Australia. Modelling of benthic habitats from animal-borne video data provides an effective approach for mapping extensive areas of the continental shelf. These data provide valuable new information on the seabed and complement traditional methods of mapping and surveying benthic habitats. Better understanding and preserving these habitats is crucial, amid increasing human impacts on benthic environments around the world

Nile Tilapia \u3ci\u3eOreochromis niloticus\u3c/i\u3e (Linnaeus, 1758) Establishment in Temperate Mississippi, USA: Multi-Year Survival Confirmed by Otolith Ages

Tolerance and adaptability to changing environmental parameters have made Nile tilapia Oreochromis niloticus (Linnaeus, 1758) a hardy and desirable aquaculture species. These traits have also enabled this fish to become a highly successful invasive species into temperate and subtropical aquatic environments. Otolith-based ages of Nile tilapia (41.3 - 400.0 mm TL, 1.34 - 1,293 g WW, n = 259) collected from a power plant cooling reservoir and the Pascagoula River proper indicated that feral populations overwintered reaching ages up to 4+ years old in coastal Mississippi, USA; these data confirm their establishment. A survey of mean daily winter (December - February) water temperatures from 2004 - 2010 in this region showed minimum lethal temperatures of \u3c 10 degrees C to occur nearly 11% of the time attesting to the adaptability of the Nile tilapia as an invasive species. One annulus (opaque zone) per year was being deposited from April to August based on marginal increment analysis along with sulcal groove length-age estimation of the young-of-the-year Nile tilapia. Additionally, life history metrics measured for this temperate population of Nile tilapia were nearly identical to those reported from African environments, indicating they are flourishing in this non-native habitat

Life History of Silver Perch Bairdiella chrysoura (Lacepède, 1803) in North-Central Gulf of Mexico Estuaries

Silver perch, Bairdiella chrysoura (Lacepède) [n = 485, 70.0–171.0 mm standard length (SL)] were collected from April 2002 through June 2003 in estuaries along the coast of Mississippi to quantify their life history. Ages estimated from sagittal otoliths ranged from 0 to 4 yr. Adult females were significantly longer and heavier than males at a given age. Silver perch became sexually mature at the end of their first year of life (0 yr), with 50% sexual maturity of the population occurring in the 91–95 mm SL size class. Gonadosomatic index (GSI) values for females began to increase in January and peaked in April (mean GSI = 11.99 ± 0.77), whereas mean male GSI values peaked in March at 1.70 (±0.11). Female silver perch were reproductively active for 6 mo, but peak spawning occurred from mid-March to June. Both oocyte maturation (OM) and postovulatory follicles (POF) were used to estimate spawning frequency. The OM method appeared to be the best estimate, paralleling most closely what was observed histologically, with spawning occurring every 1.25 d at the height of the season. Additionally, histological evidence suggested that 24% of the females sampled were capable of daily spawning. This life history information fills in data gaps to further the development of community-based models of estuarine systems, in turn facilitating best ecosystem management practices

Investigating bomb radiocarbon transport in the southern Pacific Ocean with otolith radiocarbon

To explore the transport of carbon into water masses from the surface ocean to depths of ∼1000 m∼1000 m in the southwest Pacific Ocean, we generated time series of radiocarbon (View the MathML sourceΔC14) from fish otoliths. Otoliths (carbonate earstones) from long-lived fish provide an indirect method to examine the “bomb pulse” of radiocarbon that originated in the 1950s and 1960s, allowing identification of changes to distributions of 14C that has entered and mixed within the ocean. We micro-sampled ocean perch (Helicolenus barathri ) otoliths, collected at ∼400–500 m∼400–500 m in the Tasman Sea, to obtain measurements of View the MathML sourceΔC14 for those depths. We compared our ocean perch View the MathML sourceΔC14 series to published otolith-based marine surface water View the MathML sourceΔC14 values (Australasian snapper (Chrysophrys auratus) and nannygai (Centroberyx affinis)) and to published deep-water values (800–1000 m; orange roughy (Hoplostethus atlanticus )) from the southwest Pacific to establish a mid-water View the MathML sourceΔC14 series. The otolith bomb 14C results from these different depths were consistent with previous water mass results in the upper 1500 m of the southwest Pacific Ocean (e.g. World Ocean Circulation Experiment and Geochemical Ocean Sections Study). A comparison between the initial View the MathML sourceΔC14 bomb pulse rise at 400–500 m suggested a ventilation lag of 5 to 10 yr, whereas a comparison of the surface and depths of 800–1000 m detailed a 10 to 20 yr lag in the time history of radiocarbon invasion at this depth. Pre-bomb reservoir ages derived from otolith 14C located in Tasman Sea thermocline waters were ∼530 yr∼530 yr, while reservoir ages estimated for Tasman Antarctic intermediate water were ∼730 yr∼730 yr

Distribution, Abundance, and Habitat Characterization of the Saltmarsh Topminnow, \u3ci\u3eFundulus jenkinsi\u3c/i\u3e (Everman 1892)

The saltmarsh topminnow (Fundulus jenkinsi) is federally listed as a Species of Concern due to a its rarity, impacts from human activities, and lack of information on its biology and ecology. From 2007 through 2008, we used Breder traps to fish the marsh edge on a falling tide in four regions from Louisiana through the Florida panhandle during winter, spring, and summer periods. Out of 2,108 Breder traps deployed, 661 F. jenkinsi were collected as far east as Escambia Bay, Florida, with Weeks Bay, National Estuarine Research Reserve (NERR), Alabama, yielding the highest F. jenkinsi abundance. Principal component analysis (PCA) was used to ordinate physical-chemical data into two meaningful components: a geomorphic axis (water depth, bank slope, and plant stem density) and a seasonal/spatial axis of species occurrence (water temperature, salinity, and turbidity). PCA showed a higher mean catch-per-unit-effort (CPUE) in environments comprised of low to moderate stem density (\u3c 25 stems/0.25 m-2), depth (\u3c 25 cm), bank slope (\u3c 15 degrees), turbidity (\u3c 30 NTU), and salinity (\u3c 16) coupled with spring and early summer water temperatures (\u3e 15 degrees C). F. jenkinsi CPUE was significantly higher in Spartina cynosuroides marsh edge compared with five other habitat types, even though it was one of the least sampled habitats. This species appears to be collected more frequently and in higher CPUE in small dendritic creeks off of main channels than suggested by our previous work in main channel edge habitat. This suggests that small creeks are important vectors for marsh access and supports the value of the dendritic nature of salt marshes to marsh residents

Data from: Coupling biogeochemical tracers with fish growth reveals physiological and environmental controls on otolith chemistry

Biogeochemical tracers found in the hard parts of organisms are frequently used to answer key ecological questions by linking the organism with the environment. However, the biogeochemical relationship between the environment and the biogenic structure becomes less predictable in higher organisms as physiological processes become more complex. Here, we use the simultaneous combination of biogeochemical tracers and fish growth analyzed with a novel modeling framework to describe physiological and environmental controls on otolith chemistry in an upwelling zone. First, we develop increasingly complex univariate mixed models to describe and partition intrinsic (age effects) and extrinsic (environmental parameters) factors influencing fish growth and otolith element concentrations through time. Second, we use a multivariate mixed model to investigate the directionality and strength between element-to-element and growth relationships and test hypotheses regarding physiological and environmental controls on element assimilation in otoliths. We apply these models to continuous element (Na, Sr, Mg, Ba, Li) and growth increment profiles (monthly resolution over 17 years) derived from otoliths of reef ocean perch (Helicolenus percoides), a wild-caught, site-attached, fully marine fish. With a conceptual model, we hypothesize that otolith traits (elements and growth) driven by environmental conditions will correlate both within an otolith, reflecting the time dependency of growth and element assimilation, and among individuals that experience a similar set of external conditions. We found some elements (Sr:Ca and Na:Ca) are mainly controlled by physiological processes, while other elements (Ba:Ca and Li:Ca) are more environmentally influenced. Within an individual fish, the strength and direction of correlation varies among otolith traits, particularly those under environmental control. Correlations among physiologically regulated elements tend to be stronger than those primarily controlled by environmental drivers. Surprisingly, only Ba:Ca and growth are significantly correlated among individuals. Failure to appropriately account for intrinsic effects (e.g. age) led to inflated estimates of among individual correlations and a depression of within individual correlations. Together, the lack of among-individual correlations of otolith traits in properly formulated models and the biases that can be introduced by not including appropriate intrinsic covariates suggest that caution is needed when assuming multi-elemental signatures are reflective solely of shared environments