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ASF’s Vice President of Research and Environment, Val Oullet, had a new paper published last month. Read the full paper here, or a plain language summary below:
Individual growth is crucial for the survival of fish. It affects population dynamics and resilience. While water temperature is a well-studied factor influencing fish growth, food availability and the energy required to obtain food are also important but less understood.
Collecting and analyzing data on food availability in rivers is more challenging than in lakes or oceans. This leads to gaps in knowledge about how food resources vary over time and across river networks. The concept of a “foodscape” views rivers as interconnected habitats where fish can find food. Understanding this can improve management, as well as restoration and conservation strategies for freshwater fish.
To address this, the authors of this study highlight three aspects of food availability: abundance (what’s available), accessibility (how easily fish can get it), and quality (nutritional value). The study examines how varying food availability affects juvenile salmon growth, revealing significant fluctuations throughout the year. It found that considering food variation can affect predicted growth and lead to misunderstanding the quality of different habitats.
When selecting food, fish need to deal with various factors influencing access to food, such as water temperature and flow speed, the energy expense to get it and the nutritional value of the prey.
Estimating food availability for stream salmonids is challenging due to prey variability, sampling limitations, and episodic food pulses that may be missed by low-frequency sampling. Uncertainty can result in poor management decisions, misleading habitat restoration efforts.
To assess food availability, researchers should employ diverse methods, reevaluating existing data while considering uncertainty in management decisions. Integrating food availability with factors like water flow and temperature, especially under climate change, will enhance understanding of the foodscape and improve restoration efforts. Identifying factors affecting prey availability is crucial for predicting fish growth. Sampling techniques must balance cost and precision, each with its own challenges.
The study highlights the need for greater appreciation of the role that food plays in stream fish conservation, its importance in sustaining productive and resilient fish populations, and its use for prioritizing conservation and restoration. This requires new measurement methods, studying environmental factors affecting fish diets, and developing models to predict food patterns, linking research to conservation projects to enhance strategies as environmental conditions evolve.