Effects of ambient oxygen and size-selective mortality on growth and maturation in guppies

Beatriz Diaz Pauli (1, 2, 3, 4, 5) , Jeppe Kolding (1, 3, 6) , Geetha Jeyakanth (1, 3) , Mikko Heino (7, 8, 1, 3)

1 Department of Biology
2 UiO - University of Oslo
3 Hjort Centre for Marine Ecosystem Dynamics
4 iEES Paris - Institut d'écologie et des sciences de l'environnement de Paris
5 Sorbonne Universités (COMUE)
6 International Union for Conservation of Nature
7 Norwegian Institute of Marine Research
8 IIASA - International Institute for Applied Systems Analysis

Growth, onset of maturity and investment in reproduction are key traits for understanding variation in life-history strategies. Many environmental factors affect variation in these traits, but for fish, hypoxia and size-dependent mortality have become increasingly important because of human activities, such as increased nutrient enrichment (eutrophication), climate warming and selective fishing. Here, we study experimentally the effect of oxygen availability on maturation and growth in guppies (Poecilia reticulata) from two different selected lines, one subjected to positive and the other negative size-dependent fishing. This is the first study to assess the effects of both reduced ambient oxygen and size-dependent mortality in fish. We show that reduced ambient oxygen led to stunting, early maturation and high reproductive investment. Likewise, lineages that had been exposed to high mortality of larger-sized individuals displayed earlier maturation at smaller size, greater investment in reproduction and faster growth. These life-history changes were particularly evident for males. The widely reported trends towards earlier maturation in wild fish populations are often interpreted as resulting from size-selective fishing. Our results highlight that reduced ambient oxygen, which has received little experimental investigation to date, can lead to similar phenotypic changes. Thus, changes in ambient oxygen levels can be a confounding factor that occurs in parallel with fishing, complicating the causal interpretation of changes in life-history traits. We believe that better disentangling of the effects of these two extrinsic factors, which increasingly affect many freshwater and marine ecosystems, is important for making more informed management decisions.

Mots clés: fishing selection; hypoxia; life history; Poecilia reticulata; water management

Mots clés: Eutrophication

Domaines: Sciences du Vivant [q-bio]

Beatriz Diaz Pauli, Jeppe Kolding, Geetha Jeyakanth, Mikko Heino. Effects of ambient oxygen and size-selective mortality on growth and maturation in guppies. Conservation Physiology, 2017, 5, ⟨10.1093/conphys/cox010⟩. ⟨hal-02624462⟩