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Most fish recruitment models consider only one or a few drivers in isolation, rarely include species’ traits, and have limited relevance to riverine environments. Despite their diversity, riverine fishes share sufficient characteristics that prediction of recruitment should be possible. Here we synthesize the essential components of fish recruitment hypotheses and the key features of rivers to develop a model that predicts relative recruitment strength, for all fishes, in rivers under all flow conditions. The model proposes that interactions between flow and physical complexity will create locations in rivers, at mesoscales, where energy and nutrients are enriched. The resultant production of small prey will be concentrated and prey and fish larvae located (through dispersal or retention) so that the larvae can feed, grow, and recruit. Our synthesis explains how flow and physical complexity affect fish recruitment and provides a conceptual basis to better conserve and manage riverine fishes globally.

Fishways designed for salmonids in temperate rivers have often been successful, but similar fishways provided for non-salmonid species in tropical and sub- tropical rivers have frequently failed. In 1970 a salmonid style fishway was built on a tidal barrage on the sub -tropical Fitzroy River, in Queensland, north-eastern Australia. Despite modifications to the design in 1987 assessment of the fishway in 1978 and 1992 demonstrated that it was ineffective; particularly as few barramundi (Lates calcarifer [Centropomidae]) were found at the top of the fishway. The inadequacy of the design appeared to be related to very high water velocities and turbulence within the fishway pools. Consequently, since construction of the tidal barrage many catadromous fish populations (species that live in freshwater but breed in saltwater) have declined in the freshwater reaches of the Fitzroy River. In 1994 the fishway was modified to a vertical -slot design. The study reported in this thesis is an assessment of the effectiveness of the new design from 1995 to 1997. In 38 paired samples taken at the top and bottom of the fishway, over 16 months, 29 fish species and over 23,000 fish were collected at a maximum rate of 3,400 per day. At the top of the fishway 15,471 individuals were collected and 7594 at the bottom. The migratory population consisted of 4 marine species, 9 diadtomous species and 16 potamodromous species. Common species using the fishway included blue -catfish (Arius graeffei [Ariidae]), bony herring (Nematalosa erebi [Clupeidae]), striped mullet (Mugil cephalus [Mugilidae]), barramundi, and long -finned eels (Anguilla reinhardtii [Anguillidae]). Shrimp Macrobrachium australiense [Palaemonidae]), juvenile crabs (Varuna litterata [Grapsidae]) and long -finned elvers did not ascend the full length of the fishway and specific fishways for these species are recommended. Fish between 25 and 640 mm in length ascended the fishway, although the passage of smaller size classes of immature fish was restricted which may be important for the sustainability of these migratory populations. The bulk of the biomass (71% at the top and 66% at the bottom) was made up of the diadromous blue -catfish of which 81 % were immature. Furthermore, a number of other common fish species were represented mostly by juveniles, including striped mullet, bony herring and barramundi. This study is the first record of barramundi successfully migrating through an in situ fishway in that no significant difference was found between the size of fish at the top and bottom. A major finding was that 95% of the barramundi from the fishway were immature fish (200-640 mm long), but significantly larger barramundi (maximum length 980 mm) were captured by angling near the base of the fishway. Nevertheless, enlargement of vertical -slot width from 0.15 m to 0.45 m only encouraged a small number of larger fish (890 mm maximum length) to enter. Interestingly, very small barramundi (45-163 mm long) were also absent from the fishway, but these were found in a small tidal tributary below the barrage. Very young barramundi appear to inhabit specific off - channel habitat before migrating in the main river at a larger size. The implications of these results are that 150 mm slot widths are suitable for barramundi and that different life stages have different migratory requirements.

Substrate stability is a key determinant of stream invertebrate community composition, but its measurement can be problematic. Stream ecologists often use different approaches and techniques to quantify bed stability, and this variability makes comparison among studies difficult. We examined the link between 6 reach-scale measures of substrate stability and invertebrate community metrics in 12 New Zealand mountain streams. The strength of the link varied with the method used to define substrate stability. We used morphological budgeting to measure spatial patterns and volumes of scour and fill. We found that as erosion of sediments increased, invertebrate diversity declined exponentially. In particular, increases in the volume of scour reduced taxonomic richness, whereas deposition of coarse sediments was less relevant for invertebrate communities. Overall, the distance travelled by in-situ-marked tracer stones was most strongly linked with all invertebrate community metrics, whereas the bottom component of the Pfankuch Index related very well to diversity. Both metrics showed near-linear declines in diversity with decreasing stability. In contrast, the link between invertebrate communities and the proportion of bed area affected by entrainment was weak. Therefore, we propose tracer-based indices and the Pfankuch bottom component as the most suitable measures for research involving invertebrate-substrate-stability relationships. Measures derived from in-situ-marked tracer stones reflected only entrainment and transport of particles. In contrast, the bottom component of the Pfankuch Index encompassed the widest range of bed-stability characteristics but is prone to observer bias. An objective method that combines the efficiency of the Pfankuch Index with the characteristics measured using tracer stones could serve as a powerful explanatory tool in stream ecology. © 2011 The North American Benthological Society.

This study examined the occurrence of octopus across an abalone, Haliotis laevigata, Donovan, sea ranch in south-western Australia, to understand how octopus may be impacting abalone production. Commercial divers removed 654 octopus and 17,666 empty abalone shells during regular, 2 to 4-weekly surveys over 27 months. A negative binomial generalised linear model estimated a 78% increase in empty shells per artificial abalone habitat per day, when octopuses were present, after adjusting for location and season. Of the 408 shells examined for evidence of predation, 19% had a small, slightly ovoid hole consistent with those made by octopus. The mean (± 1 SE) length of shells with boreholes (70.3 ± 2.2 mm) was significantly longer than those without (59.8 ± 0.5 mm), and boreholes were concentrated over the adductor, respiratory organs and heart. This study provides important insights into the adaptable feeding regimes of octopus and their potential to impose strong top-down controls on sea ranching operations.

Integrated aquaponic food production systems are capable of producing more food on less land using less water than conventional food systems, and marine systems offer the potential of conserving freshwater resources. However, critical factors such as suitable species combinations, environmental conditions (salinity and pH), and nutrient management (animal to plant ratio, C/N ratio, and dietary crude protein) have not been fully understood for marine systems. There were four objectives in this project. The first objective was to evaluate the growth performance of potential comparable combination (whiteleg shrimp with three halophytic plants) for the development of marine aquaponics with BFT under different salinities. The second objective was to evaluate stocking densities and the C/N ratio on growth and production of whiteleg shrimp and three halophytes. The third objective was evaluation of varying concentrations of dietary crude protein in practical diets fed to shrimp raised in biofloc aquaponic saltwater systems. The fourth objective was to evaluate effects of pH levels and additional C on the growth and production of whiteleg shrimp and five plant species in marine aquaponics. Four conclusions were determined: 1) Regarding marine aquaponics, whiteleg shrimp and the three halophytes (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) are suitable combinations for future development. According to the research results, shrimp performed better in a salinity of 15 and 20 ppt; yet, plants performed better in a salinity of 10 and 15 ppt. Therefore, a salinity of 15 ppt is suggested as the optimal saline condition for shrimp and the three halophytes in an indoor marine aquaponics system. In addition, inoculating probiotics do have the efficiency of stabilizing water quality, cultivating microbial community, and enhancing the health of shrimp and plants in the operation of aquaponics. 2) The stocking density ratio and C/N ratio exerted significant impacts on the performance of shrimp and plants in marine aquaponics. Shrimp performed better with the stocking density of 2:1 and 3:1, with no impact from the C/N ratio. Conversely, plants performed better with the stocking density of 3:1 and 5:1 with the C/N ratio at 15. Therefore, a stocking density ratio of 3:1 with a C/N ratio at 15 is suggested as the optimal condition for shrimp and the three halophytes in an indoor marine aquaponic food production system. Inoculating the water with biofloc and applying probiotics regularly can enhance the management of water quality and the health of shrimp and plants in aquaponics. 3) Among the findings of the study, shrimp growth was not affected by the protein content of the feed, suggesting that it is possible to use feeds with lower protein concentration when culturing shrimp in biofloc-based marine aquaponics. However, plants grew better in the treatments with higher protein content feed in the early and middle stages of production. Hence, for maximum production, providing a higher protein concentration feed (35 %) in the early stages of system start-up, and switching to a lower protein concentration feed (30 %) in the later stages of cultivation might be feasible. 4) The current study found no significant effects of pH or additional C on shrimp performance. In contrast, plants grew better in lower pH treatments, while additional C supplements improved the performance of plants grown in higher pH treatments and had similar results to the lower pH treatments. We suggest that RO water is not suitable source of water for shrimp-based marine aquaponics if ionic composition is not managed. The addition of C, however, led to improved growth and yields of most plants. Hence, adding C can be a promising approach in marine aquaponics to enhance the resistance to the abiotic stress of plants and improve their growth. The present study on marine aquaponics has produced important findings that will fill some knowledge gaps, provide management guidelines for production, and facilitate its development.

Offshore spring zooplankton biomass in northern Lake Michigan is currently dominated by calanoid copepods and lacking in cyclopoid copepod biomass, which is a preferred prey type for larval coregonids in the Great Lakes. As such, we survey nearshore beach zooplankton to determine if nearshore environments are following offshore trends and describe larval coregonid diets and prey selectivity during spring 2015-2019. Copepod nauplii and calanoid copepods were the most abundant prey types in the nearshore beach environments, and although larvae did not consume copepod nauplii, larvae did incorporate substantial later life stages of calanoid copepods into their diet. Additionally, larvae exhibited positive selectivity for both calanoid and cyclopoid copepods. High consumption of and selectivity for calanoid copepods in small larval coregonids is not a common observation in the Great Lakes, as previous diets of small larvae have been comprised of mainly cyclopoid copepods and cladocerans. Future research into the foraging costs and nutritional benefits of larval diets with differing ratios of cyclopoid to calanoid biomass should be investigated to understand the potential impacts of differing diets on larval growth and survival. Many species of larval fish in Lakes Michigan and Huron experience a prolonged offshore pelagic stage as during early life, but environmental conditions in offshore environments have changed in the past quarter century. Under current conditions, offshore habitats may be unsuitable for larval fish, given recent increases in offshore water clarity and decreases in offshore primary production and zooplankton biomass in both lakes. To evaluate habitat suitability for larval fish, we characterized ambient environmental conditions using data streams from multiple high frequency sensors to develop growth rate potential models as an index of habitat quality of nearshore-offshore transects in central Lake Michigan and southern Lake Huron. Since temperature regimes differ throughout the summer, we compare habitat quality throughout the summer for larval yellow perch and smelt, two species that have demonstrated offshore pelagic stages as larvae. Early in the summer, high habitat quality was concentrated nearshore, while later in the summer high habitat quality was concentrated near the thermocline, at depths where larvae are unlikely to inhabit due to limited swimming ability. The offshore (15-60 m depth contour) surface waters of both lakes provide poor habitat quality in May and July, although the surface waters of transects collected during June in southern Lake Huron provided high quality habitat at all distances from shore. These results suggest that offshore advection and prolonged offshore pelagic stage duration during early life of fish could contribute to decreased growth and survival of larval fish in lakes Michigan and Huron.

This report summarises the outcomes of the Workshop on; prioritisation of species, identification of best-practice capture and handling, design of post-release survival (PRS) studies, and development of effective communication campaigns, for developing positive behavioural change in recreational fishing of Sharks and Rays.The main objective of the national workshop was to discuss adoption of best-practice techniques by the recreational fishing sector in order to improve outcomes for fishers and animals. The specific objectives of the workshop were to:1. Identify priority species (or groups) of chondrichthyans caught by recreational fishers for the development of best-practice capture and release guidelines and post-release survival studies.2. Develop and identify key messaging for safe capture and handling to include in best-practice guidelines.3. Identify key design aspects of PRS studies needed to assess, support and refine the proposed best-practice guidelines for recreational fishers.4. Assess the best ways to communicate and extend the guidelines to recreational fishers.5. Discuss approaches for monitoring and measuring behaviour change in recreational fisheries.

Climate change is expected to significantly change the availability and trade of fishery products due to changes in the distribution and productivity of marine and freshwater species. However, the high diversity in aquatic systems and their associated fisheries result in a mosaic of impacts and responses at the local scale which have not been comprehensively documented yet. This protocol has been designed to collect standardised local level data of local fishery changes and resulting adaptations of fishing communities around the world.

Elucidation of habitat and resource use patterns is important for facilitating sustainable management of fisheries. Discrete habitats in large aquatic ecosystems may offer distinct resources and differentially affect performance. Movement of organisms and organic materials links these habitats and potentially leads to spatially complex trophic pathways between basal resources and consumers. Habitat and resource use are commonly explored via two common methods: stable isotopes and morphometric analysis. The first research chapter of this thesis employed both methods to investigate seasonal habitat use of yellow perch Perca flavescensin eastern Lake Michigan and connected waterbodies known as drowned river mouth (DRM) lakes. Landmark-based geometric morphometrics was used to compare shape differences among habitats. Stable isotopes of ambient water, otoliths, and soft tissues were compared to differentiate among habitats. Both methods provided evidence of resident nearshore Lake Michigan fish, resident DRM lake fish occupying the littoral zone, and transient Lake Michigan fish occupying the profundal zone of DRM lakes. The majority of transient Lake Michigan fish moved into the profundal zone of DRM lakes in the fall. These results support previously published genetic data of distinct populations of yellow perch in eastern Lake Michigan and connected waterbodies. The second research chapter of this thesis also employed stable isotopes and morphometric analysis, but to investigate the consistency of resource use of age-0 yellow perch in Saginaw Bay, Lake Huron. These methods served as long-term diet indicators, as compared to short-term stomach contents analysis. Both stable isotopes of soft tissues and morphometric analysis showed spatial consistency in variation among sites. Fish from the two sites closer to the tributary input had higher δ15N values and more fusiform bodies, while fish from the third site further away from the tributary had lower δ15N values and were deeper-bodied. This spatial variation supports stomach content analysis of age-0 yellow perch from a previously published study. δ13C ratios displayed annual variation, and while inconsistent with stomach content analysis, was consistent with available prey items. The findings from this study suggest that young yellow perch in Saginaw Bay have limited movement and forage in a similar area to where they were collected. Previous studies have found discrepancies among indicators and have cautioned generalization of trophic relationships when only relying on a single metric. Agreement between complementary techniques provided additional support to previously-published genetic results and stomach content data, and thereby helped more fully describe habitat use by yellow perch in these systems.