Lab report- fish behavior

Introduction:
Fish behavior can be approached from two different perspectives- an older classical nature (genetic) versus nurture (learned) point of view; and an ecological evolutionary approach.

Fish behavior includes:
1) simple neurological reflexes (avoidance or attraction) involving muscular (movement) elicited from visual, physical or chemical stimuli.
2) Complex ritual behavior including courtship or agonistic (fighting) behavior.

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In the present experiment study of the common household pet, Siamese fighting fish (Betta splendens) is done with regards to their agonistic behavior which is a complex ritual behavior. The males show their relative dominance by a series of visual displays using their fins’ swimming motion and gill cover (operculum) flaring. Whether a fish fights or flees often depends upon which fish is on the territory first, size and colour intensity.

The hypothesis
Fish with darker colors tend to have higher levels of agnostic behavior.

The null hypothesis
Color of the fish plays no role in estimating the level of aggression and hence the tendency towards agnostic behavior.

The experimental design
1) record the name of the opponent 1 fish. Gently place one Siamese fighting fish in the tank and observe the “normal” behavior after a 1-2 minute adjustment period. Do not harass the fish or let him see other fish at this time.
2) as gently as possible, place the second Betta opponent at the tank at the opposite end of the tank. In case the fish physically engage with each other, they are removed immediately and put back to their holding beakers and then placed next to each other and the reading is carried on.
3) Record and score (on the data chart) at one minute time intervals the agonistic display for each fish.
4) Tally the agonistic score for each fish to determine the most agonistic fish.

Controls
Sex of the both the fish should be same.
None of the fish should be agitated before experiment in any way.

Results
Both the fish showed high degree of agonistic behaviors including various features:
1) Charging (ChG)- a rapid swimming movement forward. Retreat is a sign of submissive behavior.
2) Fin spreading (FnS)- extension of dorsal (back) and anal (belly) fins. Fin collapsing is a sign of submissive behavior.
3) Fin beating (FnB)- a rapid movement of tail (caudal) and pectoral fins. No fin motion is a sign of submissive behavior.
4) Opercular flaring or spreading (OpS)
5) Head motion up and down. (HdM)
6) Color change- rapid increase in fin or body color intensity.

Findings
The darker color fish got an average score of 7.8 per minute whereas the lighter color fish scored 8.8 per minute based on agonistic behavior.

Discussion and conclusion
The findings of the experiment disprove the hypothesis which was based on the assumption that darker color fish are considered more aggressive by their opponents and therefore over the years have “nurtured” the aggressive behavior.
The unexpected result could have been due to undue agitation of the lighter color fish or due to low vitality and health of the darker fish which meant that the display of aggression was considerably reduced.

 

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