It is a widely held belief among those who study animals that larger size conveys some form of advantage throughout life. The idea that certain body characteristics may influence a prey's ability to survive when being attacked by a predator has received considerable attention in the past, and has been applied to a wide range of both animals and habitats. Body size, weight, growth rate, overall condition, sensory development and escape speed have all been linked to survival. Of these, body size has received the most attention from researchers, which has subsequently led to the development of a number of theories on how this characteristic may influence the predator-prey relationship. One of the most popular of these is known as the 'bigger is better' hypothesis. This theory predicts that larger body size should increase an individual's ability to escape from a predator due to the characteristics associated with this, such as overall strength and visual development. Bigger is thought to be better, but is this always the case?

A study conducted by the Australian Institute of Marine Science followed 3,000 individual coral reef fish belonging to seven different species over a period of 10 years. Researchers measured each fish at birth and tracked their survival over time. The findings showed that, contrary to the 'bigger is better' hypothesis, there was no significant correlation between initial body size and survival rate among juvenile fish. In fact, the study found that medium-sized fish showed the highest rates of survival.

Dr. Holmes explains that this may be due to the fact that medium-sized fish benefit from a unique combination of agility and size. They are large enough to avoid being eaten by the smallest predators, yet small enough to manoeuvre quickly when threatened by larger ones. This finding challenges previous assumptions about the role of body size in the survival of reef fish.

The research also examined the role of habitat in survival rates. Fish living in more complex reef environments, with greater numbers of hiding places and structural refuges, showed significantly higher survival rates regardless of body size. This suggests that environmental factors may be more important determinants of survival than previously acknowledged.

These results have significant implications for conservation efforts. Marine biologists have traditionally focused on protecting larger fish species, assuming they are more robust. The new data suggests that protection strategies should be broadened to include fish of all sizes and that habitat preservation may be even more critical than species-specific conservation efforts.