ANSWER 1

Striped Trumpeter and Bastard Trumpeter may be especially sensitive to climate change because their larvae spend a long time (1 – 6 months) drifting in the open ocean before settling onto bottom habitat. This drifting larval stage can be a long ocean journey. Along the way, survival depends on:

• water temperature,
• ocean currents,
• food availability,
• and reaching suitable habitat at the right time.

Small environmental changes during this stage can have big impacts on how many young fish survive each year.

Should we be concerned?
Research on Striped Trumpeter already shows that recruitment (the number of young fish surviving into the fishery) can vary dramatically between years.
In Tasmania, very high catches during the mid to late 1990s were linked to one or two particularly strong year classes from the early 1990s. Scientists were able to track these fish through the population using otoliths (ear bones used to age fish). This suggests that good environmental conditions during the larval phase may have created a rare “boom” in survival. Importantly, those high catches were not caused by consistently strong recruitment every year. Instead, they were largely driven by a few successful cohorts moving through the fishery over time.

How does climate affect larval survival?
Studies on Striped Trumpeter show that temperature plays a major role in larval growth and survival. Laboratory research found that warmer or cooler temperature conditions can change:

• growth rates,
• development,
• and survival of young fish.

Other modelling studies showed that ocean currents and temperature together strongly influence whether larvae survive and successfully reach coastal habitats. You can think of larvae like tiny passengers drifting along an ocean highway:

• currents determine where they travel,
• while temperature affects how well they survive the journey.

Even relatively small temperature changes may greatly alter survival during these early life stages.

What could climate change mean for future fisheries?
Around Tasmania, climate change is strengthening the East Australian Current and bringing warmer water further south. This may:

• change spawning conditions,
• alter larval transport pathways,
• and create more variable recruitment years.

Some years may still produce strong recruitment. But climate change could make these successful years less predictable. For long-lived species like Striped Trumpeter and Bastard Trumpeter, fewer strong recruitment events could slow stock recovery and reduce long-term fishery stability.

What can be done?
There are practical steps that can help improve resilience:

• protect healthy spawning populations,
• maintain enough large breeding fish,
• continue long-term monitoring,
• and adapt harvest settings when recruitment is poor.

Strong adult populations act like insurance during difficult environmental periods. More spawning fish increases the chance that enough larvae survive when ocean conditions are challenging. Fishers also play an important role by sharing observations about changing fish distribution, spawning timing, and unusual ocean conditions.

Key takeaway
Climate change is likely to make recruitment more variable and less predictable for species with long larval phases like Striped Trumpeter and Bastard Trumpeter. But there is also good reason for optimism. Australia has strong fisheries science, monitoring, and management systems. By combining fisher knowledge with climate and ocean research, the seafood sector can better adapt to changing conditions and help support sustainable fisheries into the future.

References
Choa B, Carter C, and Battaglene SC. (2010) Effects of Temperature Regime on Growth and Development of Post-Larval Striped Trumpeter (Latris lineata). https://figshare.utas.edu.au/articles/journal_contribution/Effects_of_temperature_regime_on_growth_and_development_of_post-larval_striped_trumpeter_Latris_lineata_/22878833/2.
Tracey SR, and JM Lyle. (2005) Age Validation, Growth Modelling, and Mortality Estimates for Striped Trumpeter (Latris lineata) from southeastern Australia: Making the Most of Patchy Data. Fishery Bulletin 103 (1): 1.
Tracey SR, Hartmann K, and Hobday AJ. (2012) The Effect of Dispersal and Temperature on the Early Life History of a Temperate Marine Fish. Fisheries Oceanography 21 (5): 336–47. https://doi.org/10.1111/j.1365-2419.2012.00628.x.
Tracey SR, Lyle JM, and Haddon M. (2007) Reproductive Biology and Per-Recruit Analyses of Striped Trumpeter (Latris lineata) from Tasmania, Australia: Implications for Management. Fisheries Research 84 (3): 358–67. https://doi.org/10.1016/j.fishres.2006.11.025.

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