user4748: I am currently employed on an aquaculture farm that specializes in clams and oysters. According to our modern system of taxonomy, both of these organisms are considered animals. I also know that a profession in which one trades animals is not right livelihood. However, according to this site, clams and oysters don't really have brains. Furthermore, according to wikipedia, it would seem that the nervous system of the mollusk doesn't really function to sense pleasure or pain. So, I am wondering- does trade in shellfish count as wrong livelihood? If so, how does one determine what is an animal and what is not according to Buddhism? If one is meant to go by whatever their respective society defines as an animal, surely this definition will change and therefore make this aspect of right livelihood unreliable, right?
Thankya

user7606: I asked myself the same thing once so wanted to know what makes a plant and what makes an animal. 
http://www.mcwdn.org/Plants/PlantsDiffer.html
.. if in doubt ask yourself, could I be reborn as this? In your examples I would say yes. 

user-1: Mr/Mrs Ian

"A lay follower should not engage in five types of business. Which
  five? Business in weapons, business in living beings, business in
  meat, business in intoxicants, and business in poison." AN 5.177
Pañcimā bhikkhave, vaṇijjā upāsakena akaraṇīyā. Katamā pañca:
  Satthavaṇijjā, sattavaṇijjā, maṃsavaṇijjā, majjavaṇijjā,
  visavaṇijjā. Imā kho bhikkhave, pañca vaṇijjā upāsakena akaraṇīyāti. 

Manussa would be human. An older translation of it had beings. It is unknown and unreasonable why it has been changed to "human". Atma assumes that it might be an commentary comment, developed in times when the Monks became to be more domestics and in deeper relation with those trading with animals.
One may consider this in this relation:

"There is the case where the disciple of the noble ones — using the
  wealth earned through his efforts & enterprise, amassed through the
  strength of his arm, and piled up through the sweat of his brow,
  righteous wealth righteously gained... Adiya Sutta: Benefits to be Obtained (from Wealth)

How could one enjoy his wealth knowing that it is an the cost of others?
And never ever start to think in this unwohlesome deeds justifying Mohayana development of "sentient beings". Such was never said by the Buddha. Living being, what breaths, what ever has 1, 4, 5 Aggregates. 100 Years ago people still said that animals have no feelings... or this or that being is lower, because of this and that. Even to destroy a live of a being, as (and incl.) small as the egg of a bedbug, is mentioned to be a cause of being a fault. So what ever one perceives as being a living being, one does good not to cause harm or even takes its live, acknowledge such, or move others to do so.
Actually if somebody begins to have doubt and feels his/her conscience, its a great sign and one should follow this Governing Principles
Consider that a yogi or contemplative (not to speak for a Bhikkhu/Bhikkhuni, who are even not allowed) not even keep animals or accept them.
And to ask your self in regard of livelihood, do I harm, do I use other beings, even against their will, is it dishonest livelihood, am I honest in reflecting this?
The Buddha did not talk much on the topic knowing that people are not easy able to change their ways of life, but since one has open all doors, knowing the problems before choosing a job, one does good in considering a lot and give certain possible wealth and "security" for a good sleep and the possibility to develop the path.
(Note: this answer has not been given with the agreement to be means of trade or the purpose of/for trade and/or keep people trapped and bound. How you handle it lies in your sphere, but does not excuse the deed here either.)

user254: The Vanijja Sutta is the standard definition of "wrong livelihood" and is, as you saw, not specific. It says, in its entirety (at least in this translation),

"Monks, a lay follower should not engage in five types of business. Which five? Business in weapons, business in human beings, business in meat, business in intoxicants, and business in poison.
"These are the five types of business that a lay follower should not engage in."

FYI in this commentary on the Vinaya, on page 308, it says,

Raw flesh and blood are allowed at Mv.VI.10.2 only when one is possessed
by non-human beings. Thus, in more ordinary circumstances, one may not eat
raw fish or meat even if of an allowable kind. This would include such things as
steak tartare, sashimi, oysters on the half-shell, raw eggs, and caviar.
Furthermore, even cooked fish or meat of an allowable kind is unallowable if the
bhikkhu sees, hears, or suspects that the animal was killed specifically for the
purpose of feeding bhikkhus (Mv.VI.31.14)

So, apparently, according to this, oysters (and eggs and caviar too) are considered flesh or meat.
Whether you're vegetarian is slightly up to you. This article too (of unknown authority) says not to "steam live clams or eat live oysters" but explains why it's seen as relatively OK to buy meat under certain circumstances.
There was an argument between the Buddha and Devadata apparently, with the Buddha's not mandating vegetarianism because he didn't want the Sangha to be difficult for lay people to support.
FYI one of the criteria for the "no killing" precept is whether you're conscious that the being is alive and that you intend to kill them: killing someone by accident if you thought they were already dead, for example, wouldn't be breaking the precept. So, who knows, maybe it's partly up to you decide or to be aware of whether they count as "animals" or "meat" or "sentient".
I found this modern paper which claims that they're not especially sentient, but I doubt that's canonical.
And some people would have you know that even being a vegetable farmer or crop farmer presumably wouldn't prevent the deaths of worms and possibly field mice and so on.
Anyway, good luck with finding a solution.
And don't know any context to the Vanijja Sutta (it's in the Anguttara Nikaya as a list of five things). You'd think that if "Right Livelihood" were important enough to be in the Eightfold path then it would be better defined; but maybe it's better defined for monks than it is for laypeople; or maybe it's tangential to the main message, i.e. the Buddha's messages wasn't especially about right livelihood.
The book The Buddha's Teachings on Prosperity which is a bit of compendium of rules for lay people doesn't talk about "right livelihood" exactly but does say "don't destroy life". It claims that the Gihi Sutta (although I don't see this there) says that you should avoid trapping animals unless you're too sick or weak to farm.

4748: <p>I am currently employed on an aquaculture farm that specializes in clams and oysters. According to our modern system of taxonomy, both of these organisms are considered animals. I also know that a profession in which one trades animals is not right livelihood. However, according to <a href="http://www.molluscs.at/gastropoda/index.html?/gastropoda/morphology/nervous_system.html">this site</a>, clams and oysters don't really have brains. Furthermore, according to <a href="https://en.wikipedia.org/wiki/Mollusca#Nervous_system">wikipedia</a>, it would seem that the nervous system of the mollusk doesn't really function to sense pleasure or pain. So, I am wondering- does trade in shellfish count as wrong livelihood? If so, how does one determine what is an animal and what is not according to Buddhism? If one is meant to go by whatever their respective society defines as an animal, surely this definition will change and therefore make this aspect of right livelihood unreliable, right?
Thankya</p>
 7606: <p>I asked myself the same thing once so wanted to know what makes a plant and what makes an animal. </p>

<p><a href="http://www.mcwdn.org/Plants/PlantsDiffer.html" rel="nofollow">http://www.mcwdn.org/Plants/PlantsDiffer.html</a></p>

<p>.. if in doubt ask yourself, could I be reborn as this? In your examples I would say yes. </p>
 -1: <p>Mr/Mrs Ian</p>

<blockquote>
  <p>"A lay follower should not engage in five types of business. Which
  five? Business in weapons, business in <strong>living beings</strong>, business in
  meat, business in intoxicants, and business in poison." <a href="http://zugangzureinsicht.org/html/tipitaka/an/an05/an05.177.than_en.html" rel="nofollow">AN 5.177</a></p>
  
  <p><em>Pañcimā bhikkhave, vaṇijjā upāsakena akaraṇīyā. Katamā pañca:
  Satthavaṇijjā, <strong>satta</strong>vaṇijjā, maṃsavaṇijjā, majjavaṇijjā,
  visavaṇijjā. Imā kho bhikkhave, pañca vaṇijjā upāsakena akaraṇīyāti.</em> </p>
</blockquote>

<p><em>Manussa</em> would be human. An older translation of it had beings. It is unknown and unreasonable why it has been changed to "human". Atma assumes that it might be an commentary comment, developed in times when the Monks became to be more domestics and in deeper relation with those trading with animals.</p>

<p>One may consider this in this relation:</p>

<blockquote>
  <p>"There is the case where the disciple of the noble ones — using the
  wealth <em>earned through his efforts &amp; enterprise, amassed through the
  strength of his arm, and piled up through the sweat of his brow,
  righteous wealth righteously gained</em>... <a href="http://zugangzureinsicht.org/html/tipitaka/an/an05/an05.041.than_en.html" rel="nofollow">Adiya Sutta: Benefits to be Obtained (from Wealth)</a></p>
</blockquote>

<p>How could one enjoy his wealth knowing that it is an the cost of others?</p>

<p>And never ever start to think in this unwohlesome deeds justifying Mohayana development of "sentient beings". Such was never said by the Buddha. Living being, what breaths, what ever has 1, 4, 5 Aggregates. 100 Years ago people still said that animals have no feelings... or this or that being is lower, because of this and that. Even to destroy a live of a being, as (and incl.) small as the egg of a bedbug, is mentioned to be a cause of being a fault. So what ever one perceives as being a living being, one does good not to cause harm or even takes its live, acknowledge such, or move others to do so.</p>

<p>Actually if somebody begins to have doubt and feels his/her conscience, its a great sign and one should follow this <a href="http://zugangzureinsicht.org/html/tipitaka/an/an03/an03.040.than_en.html" rel="nofollow">Governing Principles</a></p>

<p>Consider that a yogi or contemplative (not to speak for a Bhikkhu/Bhikkhuni, who are even not allowed) not even keep animals or accept them.</p>

<p>And to ask your self in regard of livelihood, do I harm, do I use other beings, even against their will, is it dishonest livelihood, am I honest in reflecting this?</p>

<p>The Buddha did not talk much on the topic knowing that people are not easy able to change their ways of life, but since one has open all doors, knowing the problems before choosing a job, one does good in considering a lot and give certain possible wealth and "security" for a good sleep and the possibility to develop the path.</p>

<p><em>(Note: this answer has not been given with the agreement to be means of trade or the purpose of/for trade and/or keep people trapped and bound. How you handle it lies in your sphere, but does not excuse the deed here either.)</em></p>
 254: <p>The <a href="http://www.accesstoinsight.org/tipitaka/an/an05/an05.177.than.html" rel="nofollow noreferrer">Vanijja Sutta</a> is the standard definition of &quot;wrong livelihood&quot; and is, as you saw, not specific. It says, in its entirety (at least in this translation),</p>
<blockquote>
<p>&quot;Monks, a lay follower should not engage in five types of business. Which five? Business in weapons, business in human beings, <strong>business in meat</strong>, business in intoxicants, and business in poison.</p>
<p>&quot;These are the five types of business that a lay follower should not engage in.&quot;</p>
</blockquote>
<p>FYI in <a href="http://www.accesstoinsight.org/lib/authors/thanissaro/bmc1.pdf" rel="nofollow noreferrer">this commentary on the Vinaya</a>, on page 308, it says,</p>
<blockquote>
<p>Raw flesh and blood are allowed at Mv.VI.10.2 only when one is possessed
by non-human beings. Thus, in more ordinary circumstances, one may not eat
raw fish or meat even if of an allowable kind. This would include such things as
steak tartare, sashimi, oysters on the half-shell, raw eggs, and caviar.
Furthermore, even cooked fish or meat of an allowable kind is unallowable if the
bhikkhu sees, hears, or suspects that the animal was killed specifically for the
purpose of feeding bhikkhus (Mv.VI.31.14)</p>
</blockquote>
<p>So, apparently, according to this, oysters (and eggs and caviar too) are considered flesh or meat.</p>
<p>Whether you're vegetarian is slightly up to you. <a href="http://www.maithri.com/articles_new/Buddhas_Advice_on_Killing_and_Consumption_of_Meat.htm" rel="nofollow noreferrer">This article too</a> (of unknown authority) says not to &quot;steam live clams or eat live oysters&quot; but explains why it's seen as relatively OK to <em>buy</em> meat under certain circumstances.</p>
<p>There was an argument between the Buddha and Devadata apparently, with the Buddha's not mandating vegetarianism because he didn't want the Sangha to be difficult for lay people to support.</p>
<p>FYI one of the criteria for the &quot;no killing&quot; precept is whether you're conscious that the being is alive and that you intend to kill them: killing someone by accident if you thought they were already dead, for example, wouldn't be breaking the precept. So, who knows, maybe it's partly up to you decide or to be aware of whether they count as &quot;animals&quot; or &quot;meat&quot; or &quot;sentient&quot;.
I found <a href="http://sentientist.org/2013/05/20/the-ethical-case-for-eating-oysters-and-mussels/" rel="nofollow noreferrer">this modern paper</a> which claims that they're not especially sentient, but I doubt that's canonical.
And some people would have you know that even being a vegetable farmer or crop farmer presumably wouldn't prevent the deaths of worms and possibly field mice and so on.</p>
<p>Anyway, good luck with finding a solution.</p>
<p>And don't know any context to the Vanijja Sutta (it's in the Anguttara Nikaya as a list of five things). You'd think that if &quot;Right Livelihood&quot; were important enough to be in the Eightfold path then <a href="http://www.accesstoinsight.org/ptf/dhamma/sacca/sacca4/samma-ajivo/" rel="nofollow noreferrer">it would be better defined</a>; but maybe it's better defined for monks than it is for laypeople; or maybe it's tangential to the main message, i.e. the Buddha's messages wasn't especially about right livelihood.</p>
<p>The book <em>The Buddha's Teachings on Prosperity</em> which is a bit of compendium of rules for lay people doesn't talk about &quot;right livelihood&quot; exactly but does say &quot;don't destroy life&quot;. It claims that the Gihi Sutta (although <a href="http://www.accesstoinsight.org/tipitaka/an/an05/an05.179.than.html" rel="nofollow noreferrer">I don't see this there</a>) says that you should avoid trapping animals unless you're too sick or weak to farm.</p>
