Empire Gudgeon

Strategic Management Prospects v4.0 Species Forecast Report created on 01 February, 2024

A Species Forecast Report is a summary of currently available information, the predicted 50-year outlook for the species, and potential pathways to recovery through species-specific and landscape-scale actions.

The report collates data from a range of sources including the Victorian Biodiversity Atlas, Strategic Management Prospects (SMP), Specific Needs Assessments, Threatened Species Action Statements, the Genetic Risk Index, and the IUCN Common Assessment Method.

Species Forecast Reports are intended to be used in conjunction with SMP and other spatial outputs in NatureKit, and Action Statements where relevant.

For more information on Species Forecast Reports, SMP and other biodiversity decision support tools, including user guides, visit Choosing actions for nature webpage on the DEECA website.

Species Overview

Taxon ID	5053
Scientific name	Hypseleotris compressa
Common name	Empire Gudgeon
Group	Fish
FFG status	Critically Endangered
EPBC status

Empire Gudgeon (Image Source: Atlas of Living Australia)

Species description

Description and life history

The Empire Gudgeon is a small and estuarine fish, growing to around 12 cm SL, with males slightly larger than females. The head and body are distinctly compressed, the body relatively deep, with a depth at pelvic fin origin 4.2-5.9 in SL. Adult males have a prominent forehead hump from above upper end of opercular margin to snout. The mouth is small, very oblique, reaching to about middle of eye; both jaws have small teeth in several rows. There are two dorsal fins; males usually have more elongate posterior second dorsal and anal fin rays, a higher first dorsal fin, and dorsal fins closer together (Gomon and Bray 2019). The sides of the body often have about 7-8 brown vertical bars, forming X-shaped marks on the midside; the base of the caudal fin has vertically elongate dark brown spot just below the midside. Dorsal fins have two black stripes, and the second dorsal has with round white spots posteriorly, surrounded by black (Gomon and Bray 2019). Individuals mature within one year, at lengths of 5.5-7.5 cm. Males establish breeding territories and display bright colours to attract a mate during the warmer months. Spawning occurs every 2-7 days over several weeks from Jasnuary to March. Females deposit adhesive eggs (0.26-0.28 mm x 0.30-0.32 mm) onto rocks, sand or weeds where they are guarded and fanned by the male. Larvae hatch at around 1.0 mm TL after 10-14 days and commence swimming at, or soon after hatching. Spawning occurs in freshwater, and the larvae are carried downstream to estuaries where they develop before migrating back to freshwater (Gomon and Bray 2019).

Distribution

To date, the taxon is only found in the Wallagaraugh River in east Gippsland at the upper end of Mallacoota Inlet; it has been recorded there on four occasions since 1980. It is very abundant in coastal streams of NSW and QLD, NT and northern WA. The Victorian populations of the taxon are on the edge of its range. It is difficult to know whether Victorian populations have been established for centuries, or are recently (decades) established due to random drift by larvae in ocean currents, or due to sea temperature rise due to climate change.

Habitat

Empire Gudgeons are found in the lower reaches of slow-flowing coastal rivers and streams, swamps, lagoons, including the upper parts of estuaries. They prefer flowing waters, and often shelter around aquatic plants and woody debris. Juveniles frequently occur in swift-flowing waters or estuaries. They are tolerant of high salinities, of water temperatures up to 35 degrees C and somewhat acidic to alkaline waters with a pH of 5.0-9.1. The fish forage amongst detritus, leaf litter and aquatic vegetation, feeding mostly on microcrustaceans, small aquatic insects, insect larvae and algae (Gomon and Bray 2019).

Genetic Risk Index

This table contains information on the genetic health of Empire Gudgeon, informed by recent work conducted by Monash University and cesar Pty Ltd (Kriesner et al. 2019; Kriesner and Weeks 2020). The project undertook genetic risk assessments of ~1,100 species of flora and fauna found in Victoria and generated a large database of available genetic and demographic data for these species. A framework was developed for combining these parameters into a Genetic Risk Index that classified species broadly into ‘Low’, ‘Moderate’, ‘High’, ‘Very High’ and ‘Uncertain’ risk categories. The Genetic Risk Index will continue to undergo refinement and validation to provide further insight into the genetic health of species in Victoria.

Total Australian population size	Greater than 10,000 individuals
Australian distribution	Most of the population occurs outside of Victoria
Dispersal capacity	High: ~32km
Reproductive mode	Sexual: species reproduces sexually via male and female gametes
Average generation time	One generation every 2 - 5 years
Victorian population trend since ~1975	Unknown
Inbreeding evidence	Low
Genetic diversity	High
Genetic rescue potential	Uncertain
Genetic Risk Index	Moderate

Species maps

Habitat Distribution Model

The Habitat Distribution Model (HDM) layer shows the modelled distribution of habitat for Empire Gudgeon in Victoria. Red shading indicates areas of habitat with relatively higher suitability, compared with yellow shaded areas. HDMs are developed by combining Victorian Biodiversity Atlas (VBA) occurrence records for the species with a range of environmental variables to predict where the most suitable habitat for the species is in Victoria. Species may not always occupy areas of suitable habitat. Threatening processes (prior or ongoing) and disturbance regimes (e.g. fire, timber harvesting) may stop species from occupying otherwise suitable habitat for periods of time. Management actions often focus on currently occupied areas, however management of unoccupied areas can also be important to allow populations to re-establish.

No Habitat Distrabution Model is currently available.

Species Forecast

No Species Forecast data is available because Empire Gudgeon is not yet included in our decision-support tools.

About Species Forecast

A Species Forecast is the estimated likelihood of a species being present in 50 years time. The data for Species Forecasts is drawn from DEECA’s decision support tools, Strategic Management Prospects and Specific Needs Assessments.

Many species benefit from the management of widespread threats, such as weeds and pests, and the benefit of these landscape-scale actions to ~4,200 species is modelled in Strategic Management Prospects. In addition to landscape-scale actions, some species also need actions that improve or protect habitat at certain sites, such as nest boxes or hollow logs, or actions to improve certain populations, such as gene mixing or translocation.

As part of a continuous improvement program for our decision-support tools, we are working to expand the scope of actions modelled in Strategic Management Prospects, and to build the dataset of species benefits from location-specific and population-specific actions.

We can use this data to consider how different actions may benefit a species and examine how different types of on-ground management may contribute to a species’ recovery in 50 years, to develop a Species Forecast.

Potential actions for species recovery

No Species Forecast data is available because Empire Gudgeon is not yet included in our decision-support tools.

Species prospects in SMP

The benefit data in SMP can be used to consider what the Empire Gudgeon’s prospects are if the landscape scale management actions in SMP are implemented.

No Species Prospects figure is available becuase Empire Gudgeon is not yet included in SMP.

How to get further information and provide feedback

For more information on the decision support tools, products and underlying data used in this report, and how the data is collected and developed into products, please visit the following links:

These links include information on how to provide data and feedback into these products.

The Species Forecast Reports will be updated periodically to reflect changes and improvements in the products and tools that inform them (e.g., following updates to SMP).

As the data contained in Species Forecast Reports is drawn from multi-species datasets, it is not currently possible to incorporate species-specific information or feedback directly.

For help or further information get in touch by visiting Choosing actions for nature webpage on the DEECA website.

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