Craig A. Boys

• PhD Applied Science
• Senior Researcher at New South Wales Department of Primary Industries

Context Modern fish-protection screens are being implemented globally to conserve aquatic ecosystems and protect water infrastructure. Australian governments have invested ~A$40 × 10⁶ towards incentive programs. However, evaluation remains limited. Aims This study aimed to review progress, summarise research, and identify future priorities for scr...

Millions of native fish are entrained into irrigation pumps in Australian rivers every year. It is often assumed these fish are wild, but stocked fish may also be affected. During fish entrainment surveys at two pump intakes on the Macquarie River, New South Wales, a noticeable increase of entrained juvenile Murray Cod ( Maccullochella peelii ) was...

Fish protection screens are being increasingly applied to prevent fish entrainment at water diversions and intakes. Screen success is thought to depend upon selecting the most suitable mesh size and ensuring appropriate water velocities around the screen. It is generally hypothesised that if fish are smaller than the mesh size, they may become entr...

Context Entrainment and removal of fish from aquatic ecosystems can occur at water pump offtakes. Exclusion screens that reduce these impacts are recognised as an important conservation measure. Aims Evaluate the effectiveness of the Australian screen design guidelines in protecting larvae and young-of-year age class of a native fish species, Murr...

River regulation and water extraction has significantly altered flow regimes and reduced flood events in many inland river systems. Environmental flows have been adopted in many systems to mitigate the ecological impacts of river regulation, however a lack of knowledge regarding the interrelationship between flow regimes, carbon transport and instr...

Each year, millions of fish are extracted from Australian waterways by the pumping and diversion of water into irrigation systems. Fish protection screens can help reduce these losses but are largely untested in Australian rivers. In this study, a large, gravity‐fed irrigation offtake on Gunbower Creek, Victoria, Australia, was investigated for fis...

Modern fish-protection screens offer significant potential benefits for Australia. The Commonwealth and New South Wales (NSW) governments have invested over $30m to incentivise early adoption by water users. However, successful adoption requires an understanding of the motivations and abilities of water users, and strategies to overcome key barrier...

There is still considerable debate as to whether the allochthonous (terrestrial) dissolved organic matter (DOM) mobilised during large flow events plays an important role in supporting secondary production in riverine food webs. Understanding how food webs respond to large pulses of terrestrial DOM (tDOM) is important for conceptualising the relati...

Freshwater inflows are linked to the abundance and catch rates of fish in estuaries. The role of terrestrial carbon resources brought into estuaries after inflows may be important, but this is currently not well understood. Therefore, we performed a study examining the effect of terrestrial dissolved organic matter (tDOM) dietary additions on the g...

Modern fish-protection screens offer significant potential benefits for Australia. The Commonwealth and New South Wales (NSW) governments have invested over $30m to incentivise early adoption by water users. However, successful adoption requires an understanding of the motivations and abilities of water users, and strategies to overcome key barrier...

The global prevalence of pumped-storage hydropower (PSH) is expected to grow exponentially as countries transition to renewable energy sources. Compared to conventional hydropower, little is currently known regarding PSH impacts on aquatic biota. This study estimated the survival of five life stages (egg, two larval stages, juvenile and adult) of r...

Mass fish kills capture the world’s attention and their frequency is increasing worldwide. The sudden death of many millions of native fish in the Darling–Baaka River in Australia in 2018–19 was a catalyst for the 11 articles in this special issue. Collectively, they advance our understanding of how to manage these events, dealing with: ecological...

Following a series of fish deaths in the lower Darling River in the austral summer of 2018–19, several field trials were undertaken over two summers to determine the efficacy of various aerators to mitigate the effects of hypoxia to prevent fish deaths. The aerators evaluated included: low-powered, solar bubble-plume diffusers; high-flow, single-po...

Climate change, river regulation and water extraction create the conditions where destratification-driven hypoxia will become more common in rivers. Preventing this and the fish deaths that can result requires options that prevent stratification and create oxygen refuges for fish. Here we discuss aeration and mixing approaches that may help prevent...

The diversion of water from rivers removes millions of fish from Australian waterways each year. Modern diversion screens are available that can reduce fish losses by 90% and stop debris entering irrigation systems. Uptake of this technology in the United States has protected fish and infrastructure. However, application in Australia has been poor...

Temperature is a key determinant that governs fish survival, reproduction, growth and metabolism. In freshwater ecosystems, anthropogenic influences have resulted in acute and prolonged temperature changes which lead to lethal and sub-lethal impacts on the biota that occupy these environments. We assessed the effects of temperature on somatic and o...

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Pumped hydroelectric energy storage (PHES) projects are being considered worldwide to achieve renewable energy targets and to stabilize baseload energy supply from intermittent renewable energy sources. Unlike conventional hydroelectric systems that only pass water downstream, a feature of PHES schemes is that they rely on bi-directional water flow...

Temperature is essential to the maintenance of optimal physiological functioning in aquatic organisms. Fish can manage natural fluctuations in temperature; however, in freshwater ecosystems acute and rapid temperature changes can originate from sources such as large dams and industrial effluents. These rapid temperature changes may induce several p...

Irrigated agriculture is vital for the food security and prosperity of people in large river basins like the Murray-Darling and Mekong. Irrigation requires water-control structures in rivers, such as weirs, sluices and regulators. Many of these structures can have negative impacts on fish. However, these impacts can be reduced if structures are des...

Fisheries in many tropical river-floodplain systems are under threat from physical obstructions caused by ongoing river infrastructure development. There is a growing need for innovative, cost-effective technologies to mitigate the impacts of these obstructions. This study examined the effectiveness of a new cone fishway for facilitating lateral mi...

Temperature plays an essential role in the ecology and biology of aquatic ecosystems. The use of dams to store and subsequently re-regulate river flows can have a negative impact on the natural thermal regime of rivers, causing thermal pollution of downstream river ecosystems. Autonomous thermal loggers were used to measure temperature changes down...

Combined fishway-culvert facilities are common in many tropical river systems in South East Asia, but little is known regarding their mutual passage effectiveness. We investigated the lateral passage of Lower Mekong Basin fish in Lao PDR, through a combined cone fishway-sluice gate culvert facility between the Mekong River and an adjacent wetland....

Many riverine fish species disperse downstream as eggs, juveniles, or adults, which can expose them to injury and death at hydraulic structures. Low-head weirs are one example of a structure that can kill fish, and this impact has been shown to be substantially higher for undershot weirs when compared to overshot weirs. In this study, autonomous se...

Irrigation infrastructure expansion threatens the diversity of freshwater fish worldwide. Irrigation infrastructure creates migration barriers which can block access to important nursery, feeding and spawning habitat. Lao PDR is a landlocked country situated within the Lower Mekong River Basin where there is a substantial dependency on rice and fis...

Egg and larval fish drifting downstream are likely to encounter river infrastructure leading to mortality. Elevated fluid shear is one likely cause. To confirm this and determine tolerable strain rates resulting from fluid shear, egg and larvae of three Australian species were exposed to a high-velocity, submerged jet in a laboratory flume. Mortali...

Irrigated agriculture and inland fisheries both make important contributions to food security, nutrition, livelihoods and wellbeing. Typically, in modern irrigation systems, these components operate independently. Some practices, commonly associated with water use and intensification of crop production can be in direct conflict with and have advers...

Globally, the extraction and diversion of water from river systems has had substantial impacts on aquatic ecosystem health and ecological processes. One such impact is the entrainment of fish at pump offtakes that can result in vast quantities of fish being permanently removed from rivers. Exclusion screens to prevent fish entrainment at pump offta...

River infrastructure poses a serious threat to diverse and productive fish stocks in many tropical river-floodplain systems; particularly the Lower Mekong River, where the fisheries are vital for food security. Dams and weirs block fish migration pathways and prevent access to feeding, spawning or nursery habitat. Fishways are becoming increasingly...

The construction of fishways for upstream and downstream connectivity is seen as the preferred mitigation measure for hydropower dams and other riverine barriers. Yet empirical evidence for effective design criteria for many species is not available. We therefore assembled a group of international fishway design experts and combined their knowledge...

Knowing the kinds of physical stress experienced by fish passing through hydropower turbines can help optimise technologies and improve fish passage. This paper assesses the hydraulic conditions experienced through three different low-head turbines (a very low head (VLH), Archimedes screw and horizontal Kaplan turbine), taken using an autonomous se...

When fish pass downstream through river infrastructure, such as dams and weirs, barotrauma may occur as a result of rapid decompression. In severe cases, barotrauma may lead to mortality. Different species are likely to respond differently to these decompressions. Therefore, to predict barotrauma for a specific species, surrogate species may not be...

The Lower Mekong Basin (LMB) is one of the most biodiverse regions in the world. It contains almost 1,100 fish species and supports a regional population of almost 60 million people. Fish provide protein, essential micronutrients and income for many of these people. Further, over 85% of fish are migratory and undertake small- and large-scale moveme...

The Lower Mekong Basin is facing unprecedented threats to fish diversity from hydropower development. There is increasing pressure on developers and construction authorities to design solutions to improve fish survival through turbines, thus protecting the resources in regions being developed for hydropower. A hydraulic characteristic of hydropower...

Egg and larval fish that drift downstream are likely to encounter river infrastructure and consequently rapid decompression, which may result in significant injury. Pressure-related injury (or barotrauma) has been shown in juvenile fishes when pressure falls sufficiently below that at which the fish has acclimated. There is a presumption that eggs...

Identifying nursery habitats for an aquatic species generally requires tracing adult individuals back through time and space to the area or habitat in which they developed as juveniles. We develop and trial a study design and analytical approach to evaluate the suitability of using stable isotopes to trace emigrating prawns to putative nursery site...

A piecewise regression approach was used to objectively quantify barotrauma injury thresholds in two physoclistous species, Murray cod Maccullochella peelii and silver perch Bidyanus bidyanus, following simulated infrastructure passage in a barometric chamber. The probability of injuries such as swimbladder rupture, exophthalmia and haemorrhage, an...

The project sought to primarily develop the first criteria for fish passage developed for Lower Mekong species but also understand the extent of current irrigation development and quantify potential social and economic benefits.

Tidally active wetlands are important nurseries for fish and crustaceans; however, urban development involving structural flood mitigation has fragmented and destroyed much of this habitat, often leading to losses in fisheries productivity. The present study demonstrated that some of these impacts may be reversible if rehabilitation projects are im...

The Hexham Swamp is a wetland of international significance in the lower Hunter River that was extensively degraded through the installation of floodgates in the early 1970s. The Hexham Swamp Rehabilitation Project was established to promote the long-term rehabilitation of this important estuarine wetland ecosystem and involved opening the eight fl...

Within the Murray-Darling Basin (MDB) many species undertake extensive downstream migrations as eggs, larvae, juveniles or adults and passage through river infrastructure has been shown to impact on their survival. The relative contribution that different stresses (such as rapid decompression and fluid shear) make to overall injury and mortality re...

‘Demonstration reaches’ are sections of river where multiple threats to native fish are addressed through river rehabilitation and strong community participation. They are an important way of promoting the key driving actions of the Murray-Darling Basin Authority's Native Fish Strategy (NFS) by using on-ground community-driven rehabilitation. Measu...

Freshwater fishes are one of the most imperiled groups of vertebrates, and population declines are alarming in terms of biodiversity and to communities that rely on fisheries for their livelihood and nutrition. One activity associated with declines in freshwater fish populations is water resource development, including dams, weirs, and hydropower f...

Tropical rivers have high annual discharges optimal for hydropower and irrigation development. The Mekong River is one of the largest tropical river systems, supporting a unique mega-diverse fish community. Fish are an important commodity in the Mekong, contributing a large proportion of calcium, protein, and essential nutrients to the diet of the...

One of the greatest threats to fish fauna in the Mekong region is the rapid expansion of river infrastructure. About 20% of the world's electricity is currently generated by hydropower and it is becoming the fastest growing renewable energy source. Currently, 14 main-stem dams are planned for the Mekong River alone and hundreds of smaller units are...

Understanding succession of fish communities associated with artificial structures is required to assess the potential of these initiatives as part of fisheries enhancement strategies and determine possible impacts on the broader ecological community. Artificial reef systems constructed in three south-eastern Australian estuaries were monitored ove...

Entrainment and impingement of two non‐salmonid species susceptible to entrainment at irrigation diversions, silver perch, Bidyanus bidyanus (Mitchell), and golden perch, Macquaria ambigua (Richardson), were examined at an experimental intake screen in a laboratory flume under a range of velocities and light levels. The presence of an intake screen...

Fish screens can help prevent the entrainment or injury of fish at irrigation diversions, but only when designed appropriately. Design criteria cannot simply be transferred between sites or pump systems and need to be developed using an evidence-based approach with the needs of local species in mind. Laboratory testing is typically used to quantify...

Research staff are now working with developers in Lao PDR and Australia to ensure design criteria is optimised at time of construction. Research is presently underway on a suite of Mekong and Murray-Darling species to identify critical tolerances of shear and pressure. Work in the USA is also being expanded to lamprey and white sturgeon in an effor...

Epizootic ulcerative syndrome was diagnosed, and the presence of Aphanomyces invadans confirmed, from an outbreak of clinical disease in wild-caught bony bream (Nematalosa erebi) from the Darling River near Bourke, in New South Wales, Australia, during 2008. This confirms a significant extension of the agent beyond its historical range.

Fish and decapod crustacean assemblages were sampled from two manipulated creeks in which tidal flow had been increased through culvert removal. Assemblages were compared to those of two control creeks where culverts remained and two reference creeks without culverts. The presence of culverts reduced the richness and abundance of estuarine–marine d...

The operation of large-scale river development projects is leading to worldwide declines in fisheries productivity. Little information is available on mechanisms influencing fish welfare and most knowledge of impacts is limited to downstream movements of salmonids. Many other species require downstream dispersal pathways and technology now exists t...

Fish passing downstream through water regulating structures such as dams and weirs can be damaged by changes in water pressure termed barotrauma. Barotrauma in some species appears to be largely due to expansion and rupture of the swim bladder, which may vary greatly with the way they regulate buoyancy. Fish with closed swim bladders (physoclists)...

Summary The impact of water diversion on fish populations is a global issue. Many countries have invested substantial funding into research and implementation strategies to ensure fish are protected at diversions that take water out of rivers for agriculture and other human uses. The most common management action is the installation of fish screens...

Epizootic ulcerative syndrome (EUS) is a fish disease of international significance and reportable to the Office International des Epizootics. In June 2010, bony herring Nematalosa erebi, golden perch Macquaria ambigua, Murray cod Maccullochella peelii and spangled perch Leiopotherapon unicolor with severe ulcers were sampled from the Murray-Darlin...

1. Estuarine wetlands are important nurseries for fish and decapod crustaceans. Flood mitigation structures (such as levees, culverts and floodgates) that fragment wetland habitat can reduce fish and crustacean passage and subsequently impact biodiversity. 2. Remediating structures to enhance connectivity, tidal flushing and fish and crustacean pas...

To provide passage for migratory native fish, a series of 14 vertical-slot and lock fishways are being constructed on the Murray River in south-eastern Australia. Three of these vertical-slot fishways, at Locks 7, 9 and 10, have a conservative slope (1V : 32H) and are designed with internal hydraulics suitable for the passage of a broad size range...

Within riverine ecosystems, physical diversity facilitates biodiversity. In particular, large wood within river channels influences the distribution of hydraulic patches and their character, within the river landscape. We surveyed 30 reaches along the Barwon-Darling River in southeastern Australia to describe their hydraulic character, before and a...

Multiple-scale assessments of fish-habitat associations are limited despite the fact that riverine fish assemblages are influenced by factors operating over a range of spatial scales. A method for assessing fish-habitat assemblages at multiple scales is proposed and tested in a large Australian dryland river, the Barwon–Darling River. Six discrete...

Intracarotid infusions of noradrenaline (0.3 nmol.kg(-1) x min(-1)) stimulated salivary fluid secretion and caused increases in salivary concentrations of protein, potassium. magnesium. chloride and phosphate, and decreases in bicarbonate. These effects of intracarotid noradrenaline were not reduced by simultaneous intracarotid infusion of phentola...