Geographical variation in age and growth of the endemic Australian sciaenid Atractoscion atelodus.

Growth rates and other age-related population characteristics are essential parameters underpinning management of a stock. This is the first study to estimate length-at-age of Atractoscion atelodus (family Sciaenidae) in New South Wales (NSW), despite the species being exploited since the 1940s. The aim of the current study was to quantify the age-based biological characteristics of A. atelodus and in particular: (a) validate the use of sagittal otoliths to quantify age; (b) estimate the growth rates and longevity of males and females; (c) examine geographical variation in age and growth; (d) document the age composition in commercial landings and (e) estimate mortality rates. A. atelodus is relatively fast growing, reaching 40 cm fork length (LF ) in the first year of life and living to at least 14 years. Growth was significantly different between sexes, with modelled asymptotic lengths of females (L∞  = 84.6 cm LF ) greater than males (L∞  = 69.0 cm LF ). Growth rates were also significantly different between northern and southern populations. Fish sampled from the southern region were younger and faster growing than those sampled in the northern region, supporting the counter-gradient growth theory and the influence of upwelling providing greater nutrient and food availability. The commercial fishery was predominantly based on young fish <3 years. with few (c. 5%) greater than 5 years. Fishing mortality estimates (F = 0.42) were similar to natural mortality estimates (M = 0.44). The age-based parameters estimated in the present study suggest that A. atelodus should be relatively resilient to fishing; nonetheless, the sizes and ages in landings are indicative of a stock heavily fished. The fishery is experiencing truncated age distributions and appears to be largely recruitment driven, increasing susceptibility to overexploitation. Determining geographical differences in growth rates of a population has important implications when considering impacts of anthropogenic drivers such as global warming and overexploitation and is important to determine in managing exploited fish populations.

Sublethal effects of a rapidly spreading native alga on a key herbivore.

Multiple anthropogenic stressors are causing a global decline in foundation species, including macrophytes, often resulting in the expansion of functionally different, more stressor-tolerant macrophytes. Previously subdominant species may experience further positive demographic feedback if they are exposed to weaker plant-herbivore interactions, possibly via decreased palatability or being structurally different from the species they are replacing. However, the consequences of the spread of opportunistic macrophytes for the local distribution and life history of herbivores are unknown.The green alga, Caulerpa filiformis, previously a subdominant macrophyte on low intertidal-shallow subtidal rock shores, is becoming locally more abundant and has spread into warmer waters across the coast of New South Wales, Australia.In this study, we measured (a) the distribution and abundance of a key consumer, the sea urchin Heliocidaris erythrogramma, across a seascape at sites where C. filiformis has become dominant, (b) performed behavioral field experiments to test the role of habitat selection in determining the local distribution of H. erythrogramma, and (c) consumer experiments to test differential palatability between previously dominant higher quality species like Ecklonia radiata and Sargassum sp. and C. filiformis and the physiological consequences of consuming it.At all sites, urchin densities were positively correlated with distance away from C. filiformis beds, and they actively moved away from beds. Feeding experiments showed that, while urchins consumed C. filiformis, sometimes in equal amounts to higher quality algae, there were strong sublethal consequences associated with C. filiformis consumption, mainly on reproductive potential (gonad size). Specifically, the gonad size of urchins that fed on C. filiformis was equivalent to that in starved urchins. There was also a tendency for urchin mortality to be greater when fed C. filiformis.Overall, strong negative effects on herbivore life-history traits and potentially their survivorship may establish further positive feedback on C. filiformis abundance that contributes to its spread and may mediate shifts from top-down to bottom-up control at locations where C. filiformis has become dominant.

The influence of climatic and lunar drivers on landings cycles of the temperate Australian sciaenid (Atractoscion atelodus) at two temporal scales: A working hypothesis for future management of this resource.

Commercial line-fishing catch rates of the endemic sciaenid Atractoscion atelodus in eastern-Australia were significantly affected by lunar phase. Periodic regression analysis indicated that catch rates were greatest during the full moon period and lowest during the new moon period. It is hypothesized that this observation is the result of the visual nocturnal feeding nature of A. atelodus, with schools of fish using the increased ambient light in the water column during the brighter part of the lunar phase to feed intensively. Increased feeding intensity during the brighter phase of the lunar month may also be related to spawning activity during the new moon phase; however this hypothesis remains to be tested. Annual commercial landings through a 71 year dataset (1950-2020) showed an approximately exponential decline, overlaid with periodic years of higher and lower landings. Such periods of higher landings were significantly positively correlated with coastal rainfall two and three years earlier, but not with rainfall in the same year or one, four or five years earlier. We hypothesize that increased coastal rainfall, likely in combination with unknown co-occurring factors, promotes increased recruitment success of A. atelodus, potentially through increased primary productivity in the nearshore marine environment. This translates into an increase in the fishable stock mainly two and three years later. If our hypothesis is correct, climate predictions of reduced rainfall in eastern Australia suggest a pessimistic outlook for this fishery.

Morphological variation of a rapidly spreading native macroalga across a range of spatial scales and its tolerance to sedimentation.

Understanding how species' traits can shape winners and losers of environmental change can help resolve drivers of current community composition patterns and predict future drivers. Sedimentation is one of the main environmental stressors shaping coastal marine communities and tolerance of high sedimentation rates (e.g. via morphological variation) may allow for competitive dominance. In New South Wales, Australia, the abundance and range of the native green macroalga Caulerpa filiformis have increased over recent decades, apparently associated with sediment disturbance. We used field measurements to test hypotheses about morphological variability in C. filiformis in relation to local- and large-scale environmental variation in water depth, sediment cover and latitude. Using a lab experiment, we tested hypotheses about survival and morphological change under different sedimentation regimes. In the field, C. filiformis fronds were more elongated and less branched when a sediment veneer is present and when water depth increased (i.e. reduced light). At larger spatial scales, frond length and width decreased with increased latitude, but latitude was less important in explaining the variation C. filiformis' length than were depth or sedimentation. Our lab experiment showed a high tolerance to sedimentation, aided by increased investment in vertical growth. This study shows that rapid morphological plasticity is a likely key attribute of the spreading native macroalga C. filiformis. We argue that having a broad environmental tolerance is key to define a species success under environmental change.

Relationships between the spread of Caulerpa filiformis and fish communities on temperate rocky reefs.

The previously sub-dominant native marine macrophyte Caulerpa filiformis is now dominant on many sub-tidal rocky reefs in New South Wales (NSW), Australia and is expanding its distribution. As C. filiformis is highly chemically defended and structurally different to co-occurring habitat-forming macrophytes, two key attributes that govern fish assemblages, we hypothesized that fish assemblages, particularly herbivorous fishes, would be different at sites where C. filiformis occurred from where it was previously absent and within sites, fish community structure would be correlated to the cover of C. filiformis. We investigated these hypotheses by determining reef-associated fish assemblage attributes (assemblage structure, species richness, total abundance, Shannon-Weiner diversity, abundance of herbivorous species) along transects within sites where C. filiformis was present and absent. Surprisingly, despite large patches and very high densities of C. filiformis on the reefs we sampled, at larger spatial scales (i.e., among sites) no fish assemblage metrics differed between sites with large stands of C. filiformis and sites without the alga. Moreover the abundance of one dominant herbivore, the rock cale Aplodactylus lophodon, was greater at sites within large beds of C. filiformis. At smaller spatial scales, however, i.e. within sites where C. filiformis was present, fish assemblages did vary as a function of C. filiformis cover along transects, although this was not consistent across sampling times. Overall, our results suggest that the potential effects of the spread of this alga on faunal communities warrants further investigation.

Habitat associations of an expanding native alga.

There are many examples of native macrophytes becoming locally dominant and spreading outside their traditional distributions, but the causes and impacts are often not understood. In New South Wales, Australia, the green alga Caulerpa filiformis is undergoing a range expansion and has transitioned from a subdominant to a dominant alga on several rocky shores around the Sydney coastline. Here we investigated relationships between established patches of C. filiformis, the habitat it occupies and associated algal communities at multiple subtidal sites over the green alga's 700 km range. We tested the following predictions: 1) C. filiformis cover differs among substrata, being greatest on turf-forming algae; 2) C. filiformis cover is positively related to environmental variables linked to increased sedimentation (e.g. reduced reef width, surface slope, increased rugosity and distance from shore); 3) occurrence of C. filiformis is associated with a change in macrophyte community structure and a reduction of macrophyte richness; 4) intact native algal canopies inhibit C. filiformis spread, but turf-forming algae and bare sand are susceptible to invasion. Substratum associations were highly consistent among sites, but contrary to our prediction, C. filiformis was most commonly associated with rock or rock + sand substratum and less frequently associated with turf-forming algae substratum. C. filiformis cover was negatively correlated with reef width, which explained most of the variation observed, although local scale variables distance from shore, reef slope, and water depth were also correlated with C. filiformis cover. Algal diversity and community composition typically differed in the presence of C. filiformis, often with a reduction of algal abundances, in particular Sargassum spp., although results varied among substrata and sites. However, monitoring of borders suggested that C. filiformis does not invade and outcompete undisturbed adjacent canopy-forming algae over a 12 month period. Our results suggest that disturbance processes (possibly linked to sedimentation) acting at the site and quadrat scale are likely important determinants of C. filiformis cover and spread, and hence its potential ecological impacts.

Application of baited remote underwater video stations to assess benthic coverage in the Persian Gulf.

A baited remote underwater video station (BRUVS) is generally considered an appropriate sampling tool for fish. The applicability of BRUVS to determine the substrate coverage was assessed by comparing stills from BRUVS videos to traditional point intercept transect (PIT) data to estimate percentage cover (PC) of different benthic substrate categories. Mean PCs of hard corals, rock, sand, and coral growth forms yielded statistically identical values with the two survey methods, while PCs of motile epibenthic invertebrates were underestimated by BRUVS in areas of both high and moderate relief. Yet, multivariate analyses revealed that the two methods yield similar substrate assemblage in an area of moderate relief. Results of our study suggest that the BRUVS can be effectively used to quantify both the presence/absence of a basic set of benthic habitat characteristics and diversity of coral growth forms on coral reefs in the Persian Gulf.

Coral reef fish assemblages along a disturbance gradient in the northern Persian Gulf: A seasonal perspective.

Seasonal dynamics of coral reef fish assemblages were assessed along a gradient of potential anthropogenic disturbance in the Northern Persian Gulf. Overall, the attributes of coral reef fish assemblages showed seasonality at two different levels: seasonal changes irrespective of the magnitude of disturbance level (e.g. species richness), and seasonal changes in response to disturbance level (e.g. total abundance and assemblage composition). The examined parameters mostly belonged to the second group, but the interpretation of the relationship between patterns of seasonal changes and the disturbance level was not straightforward. The abundance of carnivorous fishes did not vary among seasons. SIMPER identified the family Nemipteridae as the major contributor to the observed spatiotemporal variations in the composition of coral reef fish assemblages in the study area.

One new species of Micronephthys Friedrich, 1939 and one new species of Nephtys Cuvier, 1817 (Polychaeta: Phyllodocida: Nephtyidae) from eastern Australia with notes on Aglaophamus australiensis (Fauchald, 1965) and a key to all Australian species.

There are currently over 130 described species of Nephtyidae worldwide, with 18 species known from Australian waters belonging to four genera. Two new species are described, Micronephthys derupeli n. sp., and Nephtys triangula n. sp., from Eastern Australia. Descriptions are provided for all species examined. Comments are given about the recent transfer of Nephtys australiensis to Aglaophamus. A key to all Australian species of nephtyids is provided. 

Does a no-take marine protected area benefit seahorses?

Seahorses are iconic charismatic species that are often used to 'champion' marine conservation causes around the world. As they are threatened in many countries by over-exploitation and habitat loss, marine protected areas (MPAs) could help with their protection and recovery. MPAs may conserve seahorses through protecting essential habitats and removing fishing pressures. Populations of White's seahorse, Hippocampus whitei, a species endemic to New South Wales, Australia, were monitored monthly from 2006 to 2009 using diver surveys at two sites within a no-take marine protected areas established in 1983, and at two control sites outside the no-take MPA sites. Predators of H. whitei were also identified and monitored. Hippocampus whitei were more abundant at the control sites. Seahorse predators (3 species of fish and 2 species of octopus) were more abundant within the no-take MPA sites. Seahorse and predator abundances were negatively correlated. Substantial variability in the seahorse population at one of the control sites reinforced the importance of long-term monitoring and use of multiple control sites to assess the outcomes of MPAs for seahorses. MPAs should be used cautiously to conserve seahorse populations as there is the risk of a negative impact through increased predator abundance.

Limitations of habitats as biodiversity surrogates for conservation planning in estuaries.

Increasing pressures on global biodiversity and lack of data on the number and abundance of species have motivated conservation planners and researchers to use more readily available information as proxies or surrogates for biodiversity. "Habitat" is one of the most frequently used surrogates but its assumed value in marine conservation planning is not often tested. The present study developed and tested three alternative habitat classification schemes of increasing complexity for a large estuary in south-east Australia and tested their effectiveness in predicting spatial variation in macroinvertebrate biodiversity and selecting estuarine protected areas to represent species. The three habitat classification schemes were: (1) broad-scale habitats (e.g., mangroves and seagrass), (2) subdivision of each broad-scale habitat by a suite of environmental variables that varied significantly throughout the estuary, and (3) subdivision of each broad-scale habitat by the subset of environmental variables that best explained spatial variation in macroinvertebrate biodiversity. Macroinvertebrate assemblages differed significantly among the habitats in each classification scheme. For each classification scheme, habitat richness was significantly correlated with species richness, total density of macroinvertebrates, assemblage dissimilarity, and summed irreplaceability. However, in a reserve selection process designed to represent examples of each habitat, no habitat classification scheme represented species significantly better than a random selection of sites. Habitat classification schemes may represent variation in estuarine biodiversity; however, the results of this study suggest they are inefficient in designing representative networks of estuarine protected areas.

Environmental impacts of tourism in the Gulf and the Red Sea.

The Gulf and Red Sea possess diverse coastal and marine environments that support rapidly expanding mass tourism. Despite the associated environmental risks, there is no analysis of the tourism-related literature or recent analysis of impacts. Environmental issues reported in 101 publications (25 from the Gulf, 76 from the Red Sea) include 61 purported impacts (27 from the Gulf, 45 from the Red Sea). Gulf literature includes quantitative studies (68% publications) and reviews (32%), and addresses mostly land reclamation and artificial habitats. Most Gulf studies come from Iran and UAE (64%). Red Sea literature includes quantitative studies (81%) and reviews (11%), with most studies occurring in Egypt (70%). The most published topics relate to coral breakage and its management. A full account of tourism's environmental impacts is constrained by limited tourism data, confounding of impacts with other coastal developments, lack of baseline information, shifting baselines, and fragmentation of research across disciplines.

Occupational health issues in marine and freshwater research.

Marine and freshwater scientists are potentially exposed to a wide variety of occupational hazards. Depending on the focus of their research, risks may include animal attacks, physiological stresses, exposure to toxins and carcinogens, and dangerous environmental conditions. Many of these hazards have been investigated amongst the general population in their recreational use of the environment; however, very few studies have specifically related potential hazards to occupational exposure. For example, while the incidence of shark and crocodile attacks may invoke strong emotions and the occupational risk of working with these animals is certainly real, many more people are stung by jellyfish or bitten by snakes or dogs each year. Furthermore, a large proportion of SCUBA-related injuries and deaths are incurred by novice or uncertified divers, rather than professional divers using aquatic environments. Nonetheless, marine and freshwater research remains a potentially risky occupation, and the likelihood of death, injury and long-term health impacts still needs to be seriously considered.

The influence of estuarine water quality on cover of barnacles and Enteromorpha spp.

The influence of ambient water quality on the settlement of barnacles and the green alga Enteromorpha spp. to an artificial substratum in the estuaries of Sydney, Australia, was investigated to test the efficacy of both groups of organisms as indicators of changes in water quality due to urban stormwater runoff and/or sewage overflows. Wooden settlement panels were immersed for 4 months on 17 occasions between 1996 and 2005 at 11 locations known to vary in water-quality parameters (conductivity, total uncombined ammonia, oxidised nitrogen, total nitrogen, filterable phosphorus, total phosphorus, faecal coliforms and chlorophyll-a) and ambient meteorological conditions (total rainfall, maximum rainfall). Water-quality data were collected during the time that the settlement panels were deployed. Cover of barnacles was highly variable among locations (range 1.2-55.2%). Hierarchical partitioning found that chlorophyll-a, total phosphorus and total nitrogen had significant independent positive effects on barnacle cover. Together, these variables explained 26% of the variation in barnacle cover. Mean cover of Enteromorpha spp., however, did not vary significantly among locations suggesting that other potentially more important factors are influencing its settlement and growth. The results of this study suggest that barnacle cover is likely to be a useful indicator of some components of water quality.

Assessing the response of estuarine intertidal assemblages to urbanised catchment discharge.

Measurement of intertidal rock assemblages was investigated as a potential biological indicator to provide a quantitative estimate of the impact of urbanised catchment discharge on the estuaries of Sydney, Australia, from 1995 to 1999. Based on the presence and characteristics of adjacent human activities, sampling locations were categorised as: Bush; Urban; Urban with Sewer Overflows; and Industry with Sewer Overflows. In Sydney Harbour, variation in assemblage structure was measured between most impact categories, however differences between impact categories were not consistent for each year. Nevertheless, in years of above average rainfall (1998-1999), reference assemblages adjacent to national parks and distant from urbanisation were different to all other putatively impacted assemblages. Variability within assemblages was least at reference locations in each year and greatest at locations adjacent to stormwater canals and sewer overflows, particularly in 1998-1999. Variation in assemblage structure in Sydney estuaries was most strongly correlated with chlorophyll--a concentrations. Univariate analysis also identified highly significant differences for a number of factors, however, interactions between year, impact categories and location for numerous analyses, confounded the differentiation between impact categories. The results suggest that intertidal rock assemblages in Sydney Harbour and surrounding estuaries appear to be responding to the quality and quantity of discharge from urbanised catchments and, furthermore, that assemblages are more suitable than individual taxa to indicate the difference between Bush and anthropogenically disturbed estuarine locations.

Relational databases: a transparent framework for encouraging biology students to think informatically.

We discuss how relational databases constitute an ideal framework for representing and analyzing large-scale genomic data sets in biology. As a case study, we describe a Drosophila splice-site database that we recently developed at Wesleyan University for use in research and teaching. The database stores data about splice sites computed by a custom algorithm using Drosophila cDNA transcripts and genomic DNA and supports a set of procedures for analyzing splice-site sequence space. A generic Web interface permits the execution of the procedures with a variety of parameter settings and also supports custom structured query language queries. Moreover, new analytical procedures can be added by updating special metatables in the database without altering the Web interface. The database provides a powerful setting for students to develop informatic thinking skills.