Despite temperature effects on gonad development, timing of spawning is remarkably flexible in Atlantic cod

At high latitudes, early life stage survival of fish is often associated with how spawning time relates to the timing of the spring bloom. With ocean warming, basic physiological rates of ectotherms, like fish, will speed up - including gonadal development rates which dictate spawning time. Since warmer water is thought to influence the spring bloom timing differently than that of fish spawning time, the two may fall out of synchrony in the future. The precise mechanisms between temperature and gonadal development and spawning time have, however, been difficult to disentangle. Here, we take advantage of a series of independent laboratory experiments measuring individual oocyte development up to or near spawning for 153 Atlantic cod (Gadus morhua) kept between 3 and 12 °C. From these data, we derive a predictive, mechanistic equation for daily oocyte growth rate as a function of temperature and oocyte developmental status (diameter). The vitellogenic oocyte growth follows an accelerating..., All methods were carried out in accordance with relevant guidelines and regulations and also followed the ARRIVE guidelines (https://arriveguidelines.org). Permission to conduct this research at the Institute of Marine Research (IMR), Norway, was given by the Norwegian Animal Research Authority.
Temperature-controlled tank experiments of oocyte development
Our study utilises results from two different temperature-controlled experiments, the first (Experiment 1) conducted in 2005-2006 (5 and 9.6 °C) and the second (Experiment 2) in 2018-2019 (3, 6, 9, and 12 °C); further details on the methodology have been published in Kjesbu et al. (2010) and Skjærven et al. (2024), respectively.
Experiment 1 took place at the Institute of Marine Research (IMR) facilities in Bergen between June 1st, 2005 (as 2-year olds, median total length of 54 cm) and January 26th 2006 (as 3-year olds). Fish were supplied from a local rearing facility operated by the IMR in the Parisvatnet marine pond west of Bergen..., , README file for the following datasets:

### File: Oocyte_diameter_field.nc

This file describes the mean diameter of the leading cohort of oocytes from 44 female Atlantic cod caught at Smøla (63.4 °N, 8.4 °E) in 2019, and from 38 female cod caught at Austevoll (63.4 °N, 8.4 °E) in 2020 and 2021, Norway.

* ID: individual identifier
* Time: days since Jan 1st year zero
* Location: location of individual: 1=Austevoll, 2=Smøla
* Diameter: mean leading cohort oocyte diameter, μm

### File: Telemetry_data.nc

This file describes the mean daily ambient temperature (from telemetry tags) of 9 female Atlantic cod tagged at Smøla (63.4 °N, 8.4 °E) in 2018, and from 15 female cod caught and tagged at Austevoll (63.4 °N, 8.4 °E) in 2019 and 2020, Norway.

* ID: individual identifier
* Day count: days since August 31.
* Time: days since Jan 1st year zero
* Location:location of individual: 1=Austevoll, 2=Smøla
* Temperature: daily mean temperature, °C

### File: Oocyte_diameter_experiment.nc

This f...,