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AndreaNOdell / hake_growth

Spatiotemporal variation in weight-at-age and its impact on fisheries management
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weights or lengths? #3

Closed kristinmarshall-NOAA closed 2 years ago

kristinmarshall-NOAA commented 2 years ago

This is just a thought I had I wanted to capture, and get your thoughts on too.

After reading the Correa et al. paper and thinking about Maia's sablefish growth work, I began to wonder if we should be looking at the lengths in addition to, or instead of the weights? And/or thinking about modeling weight at age rather than the weight at length anomalies.

I think looking at weight deviations from the weight at length curve makes sense, and the data exploration you've done so far has shown some interesting patterns in weight anomalies - e.g. year variation seems larger than spatial variation. Essentially, those data can answer the question, are fish fatter or skinner for a given length? It might be interesting if the length data showed similar or different patterns - are fish longer or shorter for a given age? Or, similarly I guess we could use the weight data to ask, are fish bigger or smaller for a given age (not length). I would think that the weight anomalies might be more indicative of conditions during a year, or year before, and be more responsive to environmental conditions, and potentially less integrative over the life of a fish - that's a hypothesis.

From the perspective of the stock assessment - variability in weight at age is the key quantity of interest. But, that wasn't always the case. In the 2006-2010 assessments they modeled growth and length variability. It might be useful for one of us to take a look at those. Also, there is a simulation study by Peter Kuriyama from 2016 that might help us think about this as well.

We can talk more about this tomorrow, or after that.

AndreaNOdell commented 2 years ago

After doing some reading, it seems like a weight-length relationship is a good indicator of "body condition" which is often tied to fitness, reproduction, and physiological health, while weight-at-age has a temporal component, so perhaps a better indicator for growth rate. Might be worth continuing to look at both, but definitely need to think more about how they may relate to each other (or not).

kristinmarshall-NOAA commented 2 years ago

Closing this. Moved forward with weight at age, could further explore condition (weight/length) down the road.