In this guide, we discuss the fish remaining in the ocean, and on Earth.
We outline how many fish might be left, whether fish populations and numbers are increasing or decreasing, potential reasons for depletion of fish species, & whether fish are going to go extinct at some point.
Summary – Remaining Fish In The Ocean & On Earth
Why Fish Are Important
We list a few of the key reasons fish are important to ecosystems and humans in the guide below
Why Fish Counting Is Important
We list the importance of counting and monitoring fish populations and numbers in the guide below
How Many Fish Are Left In The Ocean?
One of the most recent estimates indicated there might be roughly 3.5 trillion fish in the ocean
However, there can be uncertainties in estimating fish numbers, and the number can change over time for various reasons
How Many Fish Are Left In The World?
There is not one single estimate at the moment for the total number of fish in the world across marine environments, freshwater environments, and inland fishing operations
However, it might be accurate to say that, in addition to the fish in the ocean:
– There’s a significant amount of fish in freshwater sources like lakes and rivers. About half of all fish species live in freshwater environments
– Half of all fish consumed globally come from fish farms, so, there’s also a significant amount of fish in these artificial environments (including inland farms, and fish farms located elsewhere)
How Much Have Fish Populations & Numbers Decreased/Declined Over Time?
There are variables and different factors to consider in giving an answer to this question
Some studies show that both marine and fresh water populations have generally decreased over time
There are examples though of some populations in specific climatic zones and aquatic regions that have seen population numbers increase
So, the answer is dependent on the listed variables and factors
What Are Some Of The Potential Reasons For Decreasing/Declining Fish Populations Numbers?
We list the different potential reasons for declining fish population numbers in the guide below
The Impact Of Overfishing On Fish Populations
Some reports indicate that overfishing affects a reasonable % of the world’s fisheries at the moment
Are We Running Out Of Fish Right Now?
Some studies show that some fish populations are on the decline in certain aquatic, but not in others
Will Fish Be Extinct By 2050?
Reaching critically low numbers of fish by 2050 depends on various factors and variables, which we outline in the guide below
When Will We Run Out Of Fish, Or, When Will Fish Go Extinct?
Reaching critically low numbers of fish at any point in the future depends on various factors and variables, which we outline in the guide below
What Happens If We Run Out Of Fish?
There may be significant effects on both aquatic ecosystems, and also on different parts of society, if fish numbers reach a critically low level
How To Conserve Fish Populations
We list a range of potential options that might help conserve fish populations in the future, with sustainable fishing practices, and the prevention of overfishing, being some of the main options
Are We Running Out Of Other Aquatic & Marine Life, & Also Seafood?
What we mention in the guide below, is that some studies/research also show the population numbers of some other aquatic wildlife decreasing/declining in some instances
*A Note About Fish Population Studies & Research
Different studies and research use different fishery and catchment data, and also different methods to estimate numbers such as population totals, and population decline
Some critiques are that data doesn’t fully capture total population numbers, or that data only applies to certain aquatic regions and areas and not others. These are just two examples of potential limitations of studies and research
Estimates and results from studies and research need to be weighed up against what inclusions there were in the sample data, and what methods and assumptions were used to arrive at estimates and results
Why Are Fish Important?
A few of the main reasons fish are important include, but aren’t limited to:
– They play an important role in the ecosystem
As just on example of this, fish play an important part in the nutrient cycle of aquatic environments by absorbing, transporting and excreting nutrients
– They play an important role in the food web in the wild
Different species of fish fit into different levels of the food web hierarchy in aquatic environments, with some fish being predatory fish, and some fish being prey to other aquatic predators
Some fish also eat plant life and organisms like algae
– Fish are a key food source for humans
Aside from land based agriculture, fish from the ocean and fish from inland fish farms are an important source of food for humans
– Fish play an important part in the economy
Ocean based fishing operations, and aquaculture/fish farming provide people a livelihood and income, in addition to contributing to the economy
– Other reasons
There are also other reasons fish are important, and other functions fish might fulfil that aren’t necessarily mentioned here
Why It’s Important To Monitor Fish Populations, & Count Fish Numbers
A few key reasons might be to:
– Manage key fisheries properly, and ensure fishing practices are sustainable into the future, that prevent the collapse or decline of fish populations
– Manage aquatic environments to prevent degradation, and environmental issues from occurring
How Many Fish Are Left In The Ocean?
It can be difficult to estimate the exact number of fish in the ocean at any one time
Additionally, estimates can change due to a number of reasons (such as fishing rates, production rates, environmental conditions, and so on)
One of the most recent estimates indicates there could be around 3.5 trillion fish in the ocean
From worldatlas.com: ‘The best estimates by scientists places the number of fish in the ocean at [3.5 trillion fish, across around 18,000 fish species]’
worldatlas.com also explains the different methods used to count fish numbers in the ocean in their report
How Many Fish Are Left In The World?
Fish are not just found in the ocean, but also in fresh water bodies, and at inland fish farming operations
So, the totality of fish found across all of these sources make up all the fish in the world
There’s currently no one single estimate for what the total number of fish might be across all these sources
What the information below might suggest though, is that a significant amount of fish are found in fresh water sources like rivers and lakes (about half of all fish species), and also in artificial environments like inland fish farms.
Fish In Freshwater Sources
Freshwater makes up less than 3 percent of Earth’s water supply but almost half of all fish species live in rivers, lakes, ponds, and wetlands … [and,] Worldwide, the number [of freshwater fish species] is over 10,000 species (nationalgeographic.com)
Fish In Inland Fish Farms
… about half the fish consumed globally are raised in [fish farms] (awionline.org)
In 2018, inland aquaculture [accounted for] 62.5 percent of the world’s farmed food fish production (fao.org)
Fish In Marine Fish Farms
What is unclear is whether fish in marine fish farms are included in estimates of the total amount of fish in the ocean.
So, if marine farmed fish are additional to that estimate, the number of fish in the world increases.
How Much Have Fish Populations & Numbers Decreased/Declined Over Time?
The % decline in fish population and biomass differs depending on different factors and variables, such as:
– Whether it’s marine fish populations, or freshwater fish populations being assessed
– The individual type or species of fish
– The climatic zone of the ocean
– The ocean basin or geographic region of the ocean
– The time period being measured
The information below suggests that some marine fish populations have decreased, whilst some have increased over time.
Additionally, migratory freshwater fish populations have seen a decrease over time.
Marine Fish
geographyrealm.com references a study by researchers about which involves a global long-term fishery biomass trends evaluation
The study focusses specifically on fish known to be exploited by fisheries, and covers many fish populations around the world in many different regions
Using a global fisheries database from 1950–2014, the results indicate ‘… there is a significant decline in average fishery biomass in all observed regions, across all oceans and climate zones’
Results are consistent with the point that ‘… fishery catch peaked in the 1990s, and have been declining ever since’
geographyrealm.com’s report shows a range of graphs for a range of climatic zones and ocean basins, that shows population biomass’ are consistently trending down
Population biomass decreases differ between zones and basins, but fishery populations in the ‘Indian Ocean and the southern polar Atlantic showed the greatest decline at over 50 percent’
geographyrealm.com specifically lists individual species populations that are showing decline, and mentions how many populations are showing signs having biomass levels that are unsustainable in different ways for yield, and to be part of ‘… maximal sustainable fishery catches’
Some regions have seen population increases though, with an example being in the ‘… northern Pacific – specifically the polar-boreal zone … [where] population biomass [increased] by … 800 percent’
From greenmatters.com:
… [one study sampling a third of the global catch, and not the world’s entire fish population, indicates that] the world’s [maximum sustainable yield of marine] fish populations has declined by 4.1 precent [from 1930 to 2010], primarily due to overheating oceans [caused by overfishing]
[Some fish species] responded to warming oceans positively, [but some] responded negatively
Cod, herring and certain shellfish [populations could shrink in the future]
From scientificamerican.com:
The amount of fish in the oceans has halved [/declined by 50% from 1970 to 2021, and] … populations of some commercial fish stocks [have] fallen by almost 75 percent
Migratory Freshwater Fish
[One global assessment] found that populations of migratory freshwater fish have declined by 76 percent between 1970 and 2016—a higher rate of decline than both marine and terrestrial migratory species (nationalgeographic.com)
[Some large fish weighing more than 30kg have been wiped out of most rivers] (theguardian.com)
What Are Some Of The Potential Reasons For Decreasing Fish Population Numbers?
A few reasons include but aren’t limited to:
– Overfishing, and unsustainable fishing practices
As one example, the list geographyrealm.com report indicates that ‘… overfishing … [and] seafood … being caught at rates that exceed its capacity to replenish [are issues for population and biomass decline]’
scientificamerican.com mentions that ‘[the world’s fishing fleets are too big and are supported by large subsidies, and contribute to unsustainable and destructive fishing practices]’
– Pollution in aquatic environments, and dumping into the ocean
– A changing climate and changing aquatic conditions, such as a warming temperature in the ocean
– Invasive species in aquatic environments
– Coastal development and degradation of ocean habitats
The Impact Of Overfishing On Fish Numbers & Populations
Overfishing appears affect a significant % of the worlds fisheries.
Two-thirds of the world’s fish stocks are either fished at their limit or over fished [and it’s] estimated that 70 percent of the fish population is fully used, overused or in crisis (wwf.panda.org)
There’s also other reports online that provide similar overfishing statistics across different fisheries.
Are We Running Out Of Fish?
The report by geographyrealm.com that references 2020 research data on marine fisheries, indicates that some fish biomass populations have declined rapidly over time
the theguardian.com report also indicated that some large fish types are being wiped out from some freshwater environments
So, whether we are ‘running out of fish’, or fish populations are declining to a specific point, might depend on individual species in individual environmental and geographical areas
Note that these are just two examples though. Other examples could be made of other studies and research
Will Fish Be Extinct By 2050?
greenmatters.com mentions that the claim that no fish in the oceans could be a reality by 2048 came from a nationalgeogrpahic.com report, referencing a 2006 study.
This study indicated that overfishing was the main reason for this (which causes loss of ocean biodiversity), but, they also mention the trend is reversible
Reversing trend could happen if certain sustainable practices are implemented to protect against overfishing
Note though that this is only one study
When Will We Run Out Of Fish, Or, When Will Fish Go Extinct?
At this point in time, there’s no one definitive answer to this question.
It depends on a range of variables and factors identified above in this guide.
As a summary once more, ‘running out of fish’, or fish populations decreasing to a certain number or point, might be related to the following factors and variables:
– The individual species or type of fish in question
– The environment the fish lives in i.e. the ocean, or a freshwater environment
– The climatic zone in question
– The ocean basin, or the region of ocean in question
– Reproduction and replenishment rates of fish populations vs removal and consumption rates
– Whether fishing practices are changed to support more sustainable fishery populations
– How factors like pollution, habitat degradation, and changing climate and warming ocean temperatures, invasive species, and so on, all progress in the future
– How fish farming and aquaculture progresses in the future
– Plus, other factors not mentioned here
What Happens If We Run Out Of Fish?
If fish populations begin to get critically low, the important functions that fish provide in different ecosystems, and the social and economic value that fish provide to humans could be impacted.
There may also be other effects
How To Conserve Fish Populations
A list of potential solutions might include, but aren’t limited to:
– Preventing overfishing, and implementing sustainable fishing practices
We’ve previously put together a list of sustainable fishing practices that could help preserve fish population numbers in different ways
– Consumers considering alternatives to seafood and fish as food
– Considering how humans play a role in warming ocean temperatures, and taking steps to limit our role (separate to natural variability)
– Reducing ocean pollution and ocean dumping
This is what other reports say about conserving fish populations …
Specifically in the ocean and marine environments, geographyrealm.com mentions that fish biomass population numbers can increase in regions where there are environmental changes, but also sensible fisheries management, and preventions of ‘systematic and widespread overfishing’.
geographyrealm.com also mentions that ‘clear total allowable annual catch limits, [and] securing “well-enforced and sizable no-take marine protected areas’ would help fish stocks rebuild too
From wwf.panda.org:
The best solution to the problem of declining fisheries is to rebuild overexploited stocks and ecosystems through relieving fishing pressure, improving gear selectivity and fishing exploitation patterns, protecting habitat and making a wise and generous use of protected areas and no-take zones.
From greenmatters.com:
[Consumers being aware of where their seafood comes from and buying sustainable and ethical seafood alternatives, and reducing bycatch can help preserve ocean wildlife populations]
From scientificamerican.com:
Closing fishing grounds and cracking down on illegal fishing ground [might give fishing stocks] a change to recover
Are We Running Out Of Other Aquatic Wildlife, Marine Life, & Seafood?
Several of the studies referenced in the sources listed in this guide (and other studies), include data for the populations of other wildlife, invertebrates, and aquatic and marine life over time.
Some show that other marine life populations are declining, but it differs between different species, regions on the ocean, and depending on other variables.
Sources
1. https://www.worldatlas.com/articles/how-many-fish-are-there-in-the-ocean.html
2. https://www.nationalgeographic.com/animals/fish/facts/freshwater-fish
3. https://awionline.org/content/fish-farming
4. https://www.fao.org/state-of-fisheries-aquaculture
5. https://www.theguardian.com/environment/2021/feb/23/global-freshwater-fish-populations-at-risk-of-extinction-study-finds
6. https://www.nationalgeographic.com/animals/article/migratory-freshwater-fish-decline-globally
7. https://www.geographyrealm.com/study-finds-staggering-decline-in-marine-fishery-biomass/
8. https://wwf.panda.org/discover/knowledge_hub/endangered_species/cetaceans/threats/fishstocks/
9. https://www.greenmatters.com/p/overfishing-overheated-oceans-fish-decline
10. https://www.scientificamerican.com/article/ocean-fish-numbers-cut-in-half-since-1970/
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