Authors: Bror Jonsson, Nina Jonsson and Ander G. Finstad
Source: Journal of Animal Ecology
Age of maturity is a very important aspect of growth and development that has been at the forefront of many scientific experiments over the years. Berrigan and Charnov(Berrigan & Charnov, 1994) first came up with a postulate on how the size and age of maturity of reptile and fishes were interrelated. Berrigan and Charnov through their paper, created a scientific puzzle wherein, the growth is positively correlated to slight increase in temperature, therefore creating a positive slope in the size-to-age at maturity reaction norm. On the other hand, if food is the deciding factor and not temperature, the size-to-age at maturity reaction norm has a negative slope. A significant amount of research has been conducted to understand the workings of this unique phenomenon(Perrin, 1995).
A significant amount of work has been already conducted in the last twenty years to explain the Berrigan Charnov puzzle. In a study by Jonsson & Jonsson, (2011), it was discussed that the temperature, salinity and food availability play pivotal roles in determining the weight of adults at maturity. According to Jonsson & Jonsson (2011) the somatic energy reserves of fishes are primarily used for development of primary and secondary sexual characteristics as well as for activities such as migration to breeding sites, courting, competition etc. Therefore the age at maturity, and body size are dependent on the amount of reserve energy and vice versa. According to Berrigan and Charnov (1994), ectotherms are likely to mature earlier with large r body sizes when food quality is high and they might mature earlier at lower weight when temperature is high.
The relationship between age of maturity, weight and associated environmental factors is very complex and needs further investigation for a better understanding of the underlying dynamics(Kuparinen et al., 2011). Prior to Jonsson, Jonsson, & Finstad, (2013), very few have actually taken an experimental approach to understand how temperature and food availability may affect the age of maturity and weight in ectotherms. & Atkinson (2013) came up with some plausible causal factors that might drive this unique relationship. They showed that the potential effects of the rearing temperature on optimal adult size was dependent Atkinson argue that with complete plasticity, the optimal reaction norms for the two cases are affected similarly by juvenile mortality rate and differently adult mortality rate and juvenile growth rate. In the following research article, the authors Jonsson and associates have tried to understand through simple experiments, the reaction norm between growth rate, age, and size at maturity. The authors created a tight experimental design to look at all the associated factors that could contribute to the relationship. The following study is highly interesting because this is one of the first papers that tried to answer the Berrigan Charnov Puzzle with conclusive experimental evidence. This paper provides an interesting perspective of the effects of climate change on marine environment and how it may affect marine fauna.(Jonsson & Jonsson, 2009) On the other hand, this study has implications for fisheries, where fishes are reared for economic gains and the information gathered can be used to better meet the nutritional requirements of the world population.
Review
The researchers obtained the experimental fish by breeding 20 males and 23 females that were obtained from the river Imsa. The offspring (experimental fish) were reared in a research station till they became smolts. Finally eight groups of 100 fish each i.e. 800 fish were anaesthetized and tagged with PIT tags. Next, water from the surrounding bay area was brought into eight separate water tanks and each group of 100 individuals were placed randomly in the eight tanks. Now four groups of salmons were raised in water with ambient temperature, and the other four groups were raised in water that was 2ºC warmer than the ambient temperature. The water temperature of the fish tanks were monitored regularly. Two of the four groups of fishes from each temperature regime were fed with low quality food that was low in lipids and the other two groups were fed with food that had a higher digestible energy density along with a higher lipid content. Therefore the authors, satisfied both the factors determining age at maturity and body weight at maturity. The authors had calculated the weight and size of the fish before transferring them into the seawater tanks. Later, the fish from all eight tanks were measured and weighed in October 2008, May 2009 and September 2009. Finally all fish were killed in September 15, 2009, when the experiment was completed. The authors calculated the growth in mass of the fish by using ‘Fulton’s formula’, C=100(W/L3), where C is the condition (low temp, high food quality etc.) and W is the weight of the fish, L is the length of the fish. In this setup, the condition in which the fish were kept ‘C’ was the independent variable, while the weight (W) and the length (L), and the age at maturity were the dependent variables. For each set of experiments the fish reared in normal water temperature was the baseline (control) that was compared to the growth parameters of fish reared in higher temperature. Similarly, the growth parameters of fish given low quality food was the baseline (control) and was compared to the experimental condition of higher quality of food. Authors weighed and measured all the fish that survived till the end of the study. The authors then compared the two pairs of conditions i.e. temperature and diet quality by using chi-square tests. The authors used linear regression models with temperature as the explanatory variable to model the effects of temperature, diet and their interaction on the mass of the fish. The authors also used a linear mixed effect model to factor in the results of the “random tank effect”.
Results
The results of the study showed that some of the males attained maturity in the first summer in sea water, with a higher proportion of male fish attaining maturity in tanks with higher temperature and better quality food. However, the authors found no significant difference in the age of maturity of fish reared in high temp/ low food quality vs. high temp/ high food quality tanks. One year later, the authors found that while 80-85% of the males had matured, there was significant difference in the two replicate groups housed in low temperature and low quality diet environments. Females attained maturity later compared to males, it was found that females matured faster when kept in high temp/ high quality diet environments.
The results of the study also revealed that the Atlantic salmon used in the experiments were influenced by a significant treatment effect on growth. Therefore the immature fish given better quality diet and reared at higher temperatures matured faster and had a higher mean mass. Therefore the authors could safely say that high quality diet played a role in body size at maturity. The mean mass of fish reared on low quality diets but in higher temperatures was not significantly different.
The results of this study can be used to conclusively say that temperature and quality of food are affect the age at maturity and the size of the fish at maturity. The results of the study showed that a higher temperature environment increased the chances of fish maturing early. On the other hand, a higher quality of food ensured that the fish had a higher mean mass at the time of maturity. This study effectively showcases that temperature and quality of food play a pivotal role in determining the age at maturity and the weight at maturity. Now as for the Berrigan Charnov puzzle, we can see that while the theory holds true for the age of maturity decreasing in higher temperatures, we cannot see a precise indication that the weight at maturity will also be lower at higher temperatures. As indicated in the table no2 copied from the paper we can see that the predicted vs. observed weights were either overestimated or underestimated in most cases. The study also found that the norm of reaction between age at maturity and size at maturity was gender biased as females had a higher size and growth thresholds compared to males. The authors concluded that water temperature could have affected growth rate by interacting with diet quality and consequently age at maturity. On the other hand the food quality had a more direct impact on size and age at maturity.
Comments
The experimental design of this paper was robust and the authors controlled for all other confounding factors by having a good sample size of 200 fish for each treatment. The authors have analyzed their findings using chi square and linear regression models, which are easy to understand and show the effects of the temperature and food quality precisely. The authors have also looked at the generalized linear mixed effects model to of the authors could have investigated further to see if there were any synergistic effects of the combination of high temperature and high quality food when they acted together and likewise any inhibitory effects when low temperature and low quality food were presented together. The authors did not disclose the size of the fish tank where the salmon were kept to mature. As around 100 salmons were kept in each fish tank, a small tank would limit the amount of movement and energy expenditure by the fish and thereby result in a bigger mass. The authors also did not clarify, how they standardized the experiment so that all fish (800) consumed the same amount of food. If the food was dropped in the tank, the fish nearest would feed on it more than others, we cannot eliminate the chances of competition in the tank. The authors used the spawn of three females fertilized by two males, however this could have resulted in genetic variation in the progeny, which could add noise to the data of body weight as some individual fish might be pre-dilected to grow bigger than others. The results of the study would have been more convincing if the 800 fish were brought from the same stock i.e. one mother and one father.
Bibliography
Berrigan, D., & Charnov, E. L. (1994). Reaction norms for age and size at maturity in response to temperature: a puzzle for life historians. Oikos, 474–478.
Jonsson, B., & Jonsson, N. (2009). A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flow. Journal of Fish Biology, 75(10), 2381–2447.
Jonsson, B., & Jonsson, N. (2011). Ecology of Atlantic salmon and brown trout: habitat as a template for life histories (Vol. 33). Springer.
Jonsson, B., Jonsson, N., & Finstad, A. G. (2013). Effects of temperature and food quality on age and size at maturity in ectotherms: an experimental test with Atlantic salmon. Journal of Animal Ecology, 82(1), 201–210.
Kuparinen, A., Cano, J. M., Loehr, J., Herczeg, G., Gonda, A., & Merilä, J. (2011). Fish age at maturation is influenced by temperature independently of growth. Oecologia, 167(2), 435–443.
Perrin, N. (1995). About Berrigan and Charnov’s life-history puzzle. Oikos, 73, 137–139. Retrieved from http://www.jstor.org/stable/3545737
Reasons behind choosing two in-text citations from the present article
- Jonsson, B., & Jonsson, N. (2009). A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flow. Journal of Fish Biology, 75(10), 2381–2447.
I chose this paper from the article because climate change is a reality that we have to accept as we might have crossed the point of no returns. Under such circumstances, it is important to look at the possible effects of climate change on marine ecosystems. This study has serious implications on the future of the world that we live in, since a misbalanced marine ecosystem is likely to have a huge impact on world economy, biodiversity and may have a cascade effect on the rest of the biomes.
- Kuparinen, A., Cano, J. M., Loehr, J., Herczeg, G., Gonda, A., & Merilä, J. (2011). Fish age at maturation is influenced by temperature independently of growth. Oecologia, 167(2), 435–443.
This paper by Kuparinen and associates is a perfect addition to the present study and looks at only the temperature and its effects on the age of maturation. This study gets rid of the additive effects of food quality and high temperature and picks a single factor and that plays a role in modifying the life history traits of fish.
Outside citations
- Adolph, S. C., & Porter, W. P. (1996). Growth, seasonality, and lizard life histories: age and size at maturity. Oikos, 267–278.
- Bonada, M., & Sadras, V. O. (2014). Review: critical appraisal of methods to investigate the effect of temperature on grapevine berry composition. Australian Journal of Grape and Wine Research.
- Brander, K. (2010). Impacts of climate change on fisheries. Journal of Marine Systems, 79(3), 389–402.
- Hare, S. R., & Francis, R. C. (1995). Climate change and salmon production in the Northeast Pacific Ocean. Canadian Special Publication of Fisheries and Aquatic Sciences, 357–372.
- Jeppesen, E., Meerhoff, M., Holmgren, K., González-Bergonzoni, I., Teixeira-de Mello, F., Declerck, S. A. J., Bjerring, R. (2010). Impacts of climate warming on lake fish community structure and potential effects on ecosystem function. Hydrobiologia, 646(1), 73–90.
- Potts, W. M., Booth, A. J., Richardson, T. J., & Sauer, W. H. H. (2014). Ocean warming affects the distribution and abundance of resident fishes by changing their reproductive scope. Reviews in Fish Biology and Fisheries, 24(2), 493–504.
- Wood, C. M., & McDonald, D. G. (1997). Global warming: implications for freshwater and marine fish. Cambridge University Press.
I want to look at how fluctuations in temperature can alter the age and size at maturity, therefore I will keep the 50 fish in five groups baseline (normal temp), -1 ºC below normal, -2 ºC below normal, +1ºC above normal , and +2ºC above normal, and the last group at normal temperature with 10 fish in each group. All groups will be given same amount of food. I will use the thermal gradient to understand the changes in growth rate, age and size at maturity. The independent variable for this study will be the temperature of the water tank and the dependent variables will be the growth rate(R), age (A), weight(W), and length (L)at maturityThe Based on the results I will try to fit a regression model on how changes in temperature affects, age and size at maturity.
Abstracts
- Jonsson, B., & Jonsson, N. (2009). A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flow. Journal of Fish Biology, 75(10), 2381–2447.
The present paper reviews the effects of water temperature and flow on migrations, embryonic development, hatching, emergence, growth and life-history traits in light of the ongoing climate change with emphasis on anadromous Atlantic salmon Salmo salar and brown troutSalmo trutta. The expected climate change in the Atlantic is for milder and wetter winters, with more precipitation falling as rain and less as snow, decrease in ice-covered periods and frequent periods with extreme weather. Overall, thermal limits for salmonids are species specific. Scope for activity and growth and optimal temperature for growth increase with temperature to an optimal point before constrain by the oxygen content of the water. The optimal temperature for growth decreases with increasing fish size and varies little among populations within species, whereas the growth efficiency may be locally adapted to the temperature conditions of the home stream during the growth season. Indirectly, temperature influences age and size at smolting through its effect on growth. Time of spawning, egg hatching and emergence of the larvae vary with temperature and selective effects on time of first feeding. Traits such as age at first maturity, longevity and fecundity decrease with increasing temperature whilst egg size increases with temperature. Water flow influences the accessibility of rivers for returning adults and speed of both upstream and downstream migration. Extremes in water flow and temperature can decrease recruitment and survival. There is reason to expect a northward movement of the thermal niche of anadromous salmonids with decreased production and population extinction in the southern part of the distribution areas, migrations earlier in the season, later spawning, younger age at smolting and sexual maturity and increased disease susceptibility and mortality. Future research challenges are summarized at the end of the paper.
- Kuparinen, A., Cano, J. M., Loehr, J., Herczeg, G., Gonda, A., & Merilä, J. (2011). Fish age at maturation is influenced by temperature independently of growth. Oecologia, 167(2), 435–443.
Age and size at maturation are important correlates of fitness in many organisms and understanding how these are influenced by environmental conditions is therefore required to predict populations’ responses to environmental changes. In ectotherms, growth and maturation are closely linked to temperature, but nonetheless it is often unclear how temperature-induced variation in growth and temperature per se translate to the process of maturation. Here, we test this explicitly with a common garden experiment using nine-spined sticklebacks (Pungitius pungitius). We reared fish in 14 and 17°C and recorded high resolution growth trajectories and the timing of maturation on an individual basis. To characterize the growth of each individual, we fitted a von Bertalanffy growth curve to each measured growth trajectory, so that the three parameters of the curve provided a summary of an individual’s growth. Temperature treatments induced changes in both the growth parameters and the age at maturation. In females, changes in the age of maturation were encompassed by variations in growth, whereas in males there was a temperature-related shift in the age at maturation that was unrelated to growth. Our experiment demonstrates that temperature can affect maturation directly, and not only through temperature-induced changes in growth. Therefore, one cannot predict, on the basis of growth only, how changes in temperature might alter age and size at maturation and the subsequent reproduction.
