The Delta Smelt Is An Endangered Species

Since the beginning of time, all species have gone, and continue to go, through the process of natural selection which forces either evolution or extinction. As time goes on, some species are being unjustly threatened with the possibility of extinction due to rapid changes within their environments. One of the main factors that are destined to drive species to extinction is artificial selection through human activity and its effect on climate change. Temperatures are changing at an alarming rate causing problems throughout different ecosystems making it crucial to study its effects on wildlife.

The research article selected by the group, “Ontogeny influences sensitivity to climate change stressors in an endangered fish”, deals directly with how predicted temperature and salinity changes in the San Francisco Estuary will affect the several life stages of the Delta Smelt.

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The experiments conducted on the Delta Smelt within this article provides important information for both fields of research concerning conservation ecology and conservation physiology. The Delta Smelt, an endangered species, is a crucial part of the San Francisco Bay ecosystem.

Due to its importance within the food chain, it is labeled as an indicator species meaning that the condition of the Delta Smelt gives researches insight into how well the estuarine ecosystem is performing.

The objective of the research is to aid in balancing both ecosystem restoration and ecosystem services by providing information that will assist in finding the best management actions that can accommodate both tasks. The research team made the prediction that the temperature and salinity tolerances will vary across the various life stages of the Delta Smelt. The Delta Smelt has a lifespan of about a year composed of five different ontogenetic stages that differ in regions inhabited and seasons. This was an important factor when deciding on how to separate the stages into the five different groups of larval, post-larval, juvenile, adult, and post-spawning adult. After separating the different life stages, they proceed to test each of the stages of thermal tolerance. First they performed a chronic lethal maximum experiment, on only post-larval stages, by acclimating them at around 18℃ for three weeks and then proceeding to increase the temperature 1℃ a day until one hundred percent mortality was reached. This procedure was used to discover their upper thermal acclimation limits. Next, researchers moved on to finding upper-temperature tolerance through their critical thermal maximum experiments. For this part of the research post-larval fish were split into three acclimation groups, low (12.0–12.5°C), medium (15.5–16.5°C), and high (18.5–19.5°C), and kept in these conditions for three weeks. After the three week acclimation period fish were randomly selected to be placed into a tank where they had 30-45 minutes before the temperature started to increase by 0.3°C per minute. The experiment continued until unusual behavior was observed indicating what would be ecological death. These experiments were then used to calculate the warming tolerance for each stage.

Warming tolerance is the difference between the temperature indicating ecological death and the current habitat temperature. This gives numerical values to how much the temperatures in their ecosystem can rise before the species is unable to live. The next portion of experiments conducted were used to test the Smelt ’s salinity tolerance which is the amount of salt concentration within a certain amount of water that permits survival. This experiment was conducted for the juvenile and adult stages by placing them into three separate tanks and then after acclimation researches started to increase the amount of artificial sea salt by 2.0 ppt every 12 hours. Salinity was increased until one hundred percent mortality or sea water conditions were met. If the sea water conditions were met then fish were held at 34.0 ppt for 3 weeks and monitored. After this experiment, they followed it by acute salinity maximum experiment starting different stages at selected salinities and increasing slowly until a target salinity, determined by the previous experiment, was reached. Afterward, fish from each of the three salinity treatments were randomly selected for assessment to see possible differences in thermal tolerance after subjection to salinity stress.

The data collected from the experiments detailed above confirmed to the researchers that the different ontogenetic stages within the Delta Smelt lifespan have differing thermal and salinity tolerances. It was found that thermal tolerance was highest in larval fish and each succeeding stage showed lower tolerance than the next with a small exception between juvenile and adult. The warming tolerance calculated from these result have juveniles exhibiting the lowest thermal tolerance followed by late-larval, larval, adults, and then post-spawning adults. The experiments performed in the salinity tolerance experiments revealed that increased salinity only affect survival at extreme conditions and did not impact thermal tolerance. The research conducted in this research article is critical to conservation management. The findings are especially important to species that confined to a specific area that are unable to move to more favorable living conditions. Understanding the effects that climate change will have on individual species will help the overall conservation of the ecosystem. The experiment performed within the article include most of the stages but exclude some larval and post-larval due to the required living conditions. If these stages were included in all of the experiments then it might provide for a slight increase in accuracy. Other than that the experiments conducted. Overall the hypothesis made at the beginning of the research was justified by the data collected from the experiments.