Distribution and movement of catadromous fish: design and implementation of a freshwater-estuarine acoustic telemetry array

Movement patterns of two co-occurring catadromous fishes, estuary perch Macquaria colonorum and Australian bass Macquaria novemaculeata, were investigated in a large tidal river in southeastern Australia. Nineteen estuary perch and seventeen Australian bass were captured as mature adults from the Shoalhaven River, surgically implanted with electronic transmitters and released. Forty-nine Vem- co (VR2W) acoustic receivers were strategically placed throughout the river from the Tallowa Dam wall downstream to the sea (a distance of 75 km). Between September 2007 and February 2008, a total of 800,263 detection events were recorded with most fish detected in the middle (estuary perch) to upper (Australian bass) estuarine reaches of the river. Both species made extensive use of the estuary, with no estu- ary perch and only three Australian bass entering the freshwater, indicating that the freshwater residency phase of these catadromous fishes may not be obligatory. The data also suggests that estuary perch and Australian bass exhibit high site fidelity, which, along with their large scale movements may be influenced by factors such as river discharge and prey availability. This large freshwater-estuarine telemetry array combined with critical abiotic information (river discharge and salinity) has and will provide a greater understanding of catadromous fish movement, particularly in relation to habitat utilization and environmental flows

Seasonal residency and movement patterns of two co-occurring catadromous percichthyids within a south-eastern Australian river

Understanding movement patterns and habitat utilisation is critical for the management of diadromous fishes. An acoustic telemetry array was used to monitor 33 estuary perch, Macquaria colonorum and 39 Australian bass, Macquaria novemaculeata in the freshwater and estuarine reaches on the Shoalhaven River, south-east Australia. On average, tagged M. novemaculeata were detected for a considerably shorter period than M. colonorum, and evidence suggested that fishing pressure may have impacted on their survival. Macquaria colonorum displayed significant shifts in seasonal and size-related habitat use, with fish predominantly residing in deep (\u3e5 m) areas within the middle (mesohaline) reaches of the estuary during the austral spring to autumn months. In winter, M. colonorum individuals made frequent downstream migrations, often to localised areas, within the lower estuary (LE). In contrast, M. novemaculeata were distributed in shallow (m) habitats throughout the year, within the upper (oligohaline) estuarine reaches of the river, as well as in fresh water. Like M. colonorum, M. novemaculeata made extensive downstream and upstream movements, often coincident with reproductive behaviour, water temperature and increased freshwater inflows. It is postulated that the high site fidelity and repetitive homing displayed by both species is influenced by ontogenetic behaviour and prey availability. Furthermore, the extent of instream distribution by both species, and the lack of observed annual spawning migrations by some M. novemaculeata individuals, indicates the once considered \u27catadromous\u27 life cycle of these fishes may not be obligatory. A management approach is recommended to ensure that both these species are not over-exploited within a portion of their instream range, thus maintaining their full reproductive potential

Shock, stress or signal? Implications of freshwater flows for a top-level estuarine predator.

Physicochemical variability in estuarine systems plays an important role in estuarine processes and in the lifecycles of estuarine organisms. In particular, seasonality of freshwater inflow to estuaries may be important in various aspects of fish lifecycles. This study aimed to further understand these relationships by studying the movements of a top-level estuarine predator in response to physicochemical variability in a large, temperate south-east Australian estuary (Shoalhaven River). Mulloway (Argyrosomus japonicus, 47-89 cm total length) were surgically implanted with acoustic transmitters, and their movements and migrations monitored over two years via fixed-position VR2W acoustic receivers configured in a linear array along the length of the estuary. The study period included a high degree of abiotic variability, with multiple pulses (exponentially high flows over a short period of time) in fresh water to the estuary, as well as broader seasonal variation in flow, temperature and conductivity. The relative deviation of fish from their modal location in the estuary was affected primarily by changes in conductivity, and smaller fish (n = 4) tended to deviate much further downstream from their modal position in the estuary than larger fish (n = 8). High-flow events which coincided with warmer temperatures tended to drive mature fish down the estuary and potentially provided a spawning signal to stimulate aggregation of adults near the estuary mouth; however, this relationship requires further investigation. These findings indicate that pulse and press effects of freshwater inflow and associated physicochemical variability play a role in the movements of mulloway, and that seasonality of large freshwater flows may be important in spawning. The possible implications of river regulation and the extraction of freshwater for consumptive uses on estuarine fishes are discussed

Tagging information for mulloway tracked in the Shoalhaven River.

1<p>Sex is male (M), female (F), or juvenile (J). Sex could not be conclusively identified for all samples (U).</p>2<p> refers to the model distance-to-sea value determined from the kernel density distributions for each fish (see Methods).</p>3<p>Linear distance (km) along the estuary encompassed by the 50^th and 90^th percentile of the kernel density distribution.</p

Parameter summaries and associated statistics for best non-ARMA model and the best ARMA model presented in Table 2, fitted to the linear deviation of <i>Argyrosomus japonicus</i> from its average location along the length of the river (<i>Dev</i>).

<p>Parameter summaries and associated statistics for best non-ARMA model and the best ARMA model presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095680#pone-0095680-t002" target="_blank">Table 2</a>, fitted to the linear deviation of <i>Argyrosomus japonicus</i> from its average location along the length of the river (<i>Dev</i>).</p

Visual interpretation of significant <i>Cond·TL</i> interaction term, showing that smaller mulloway (solid line) display a much more pronounced response to variation in conductivity than larger mulloway (dashed line).

<p>Visual interpretation of significant <i>Cond·TL</i> interaction term, showing that smaller mulloway (solid line) display a much more pronounced response to variation in conductivity than larger mulloway (dashed line).</p

Parameter summaries and associated statistics for best non-ARMA model and the best ARMA model presented in Table 4, fitted to the depth of tagged <i>Argyrosomus japonicus</i> (Table 1).

<p>Parameter summaries and associated statistics for best non-ARMA model and the best ARMA model presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095680#pone-0095680-t004" target="_blank">Table 4</a>, fitted to the depth of tagged <i>Argyrosomus japonicus</i> (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095680#pone-0095680-t001" target="_blank">Table 1</a>).</p

Mean daily position relative to estuary mouth (km), temperature (°C) and conductivity (ms µs⁻¹, primary <i>y</i>-axis, black line, dashed line and light grey line respectively), and mean daily inflow measured at the Grassy Gully gauging station (secondary <i>y</i>-axis, dark grey line) during the study period for Fish 2 (a) and Fish 11 (b).

<p>Mean daily position relative to estuary mouth (km), temperature (°C) and conductivity (ms µs⁻¹, primary <i>y</i>-axis, black line, dashed line and light grey line respectively), and mean daily inflow measured at the Grassy Gully gauging station (secondary <i>y</i>-axis, dark grey line) during the study period for Fish 2 (a) and Fish 11 (b).</p

Tagging information for mulloway tracked in the Shoalhaven River.

1<p>Sex is male (M), female (F), or juvenile (J). Sex could not be conclusively identified for all samples (U).</p>2<p> refers to the model distance-to-sea value determined from the kernel density distributions for each fish (see Methods).</p>3<p>Linear distance (km) along the estuary encompassed by the 50^th and 90^th percentile of the kernel density distribution.</p