Aim To find out the endurance of freshwater fish to salinity in water and to study the diet of the freshwater fish. Basic principle




Дата канвертавання27.04.2016
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Biology experiment

Group members: Chan Wai Lan (2) Class :6B

Ma King Man (6)

Cheung Wai Tong (12)



Topic: The study of the tolerance of freshwater fish to salinity and diet of the freshwater fish

Aim

To find out the endurance of freshwater fish to salinity in water and to study the diet of the freshwater fish.



Basic principle

To find out the changes in the behavior of fishes by increasing the salinity of the water. We increased the percentage of the salinity of the water by 10% each two days by adding certain amount of salt.

By observing the experimental fish and recording the times of their deaths, so that survival time can be considered in relation to the salinity.

Details of the freshwater fish

Family: minnow

Common name: Golden tiger barb

Scientific name: Capoeta tetrazona





Feeding Habits
Fresh spinach, zucchini, peas and lettuce. Live blood worms, glass worms, brine shrimp and tubifex worms. Frozen vegetable diet, daphnia, plankton, beef heart, brine shrimp, glass worms and blood worms. Flake and freeze dried foods also accepted.

Compatibility


Extremely active schooling fish that will harass smaller fish and slow moving fish. Recommended for the active aquarium only.

Habitat
Indonesia-Borneo: Moderately decorated with rocks, live plants and driftwood. Live plants may be nibbled on.

Breeding
Adult males display more red coloration in their fins and nose area.

Additional Comments


There is a misconception that all the members of the Barb Family are aggressive towards other tank mates. Tiger Barbs are very active fish and if kept in schools of five or more they usually stick to themselves, and not bother the other fish in the aquarium as often as one or two Tiger Barbs would.


Family: Tetraodontidae

Common name: Green Puffer

Scientific name: Tetraodon fluviatilis




Physical description:

  • Size: up to 6 inches (15 cm). 

  • Strata: bottom, middle. 

  • pH range: 7.5 to 8.5.

  • Temparature: 75 to 82F (24 -28C).

  • Color: white underbelly and yellow/green top covered in black spots, this top coloring ranging from dark green to fluorescent green to yellow.

  • Very thick set and shaped, protruding eyes and very broad forehead.

  • Fan shaped Caudal fin and no Ventral fins. 

  • The body covered with small spines and leathery texture skin.

General information:

Puffers are of the family Tetraodontidae, meaning four toothed. They have a club-shaped and unarmored body. Green Puffer is a freshwater to light brackish species inhabiting rivers, lakes and flood plains. It is mostly carnivorous (mollusks, crustaceans, invertebrates) and also will eat vegetation. Generally a peaceful fish, but as it gets older it can get more aggressive, especially, when harassed by potential predators and a notorious fin-nipper. Green puffer with a smooth belly is very popular, it is often confused wity t. nigroviridis, and also t. schoutedeni, which are more club-shaped. The green puffer exhibits a torpedo shaped body, with a longer sloping head and back region.


 


 T. fluviatilis


 T. nigroviridis

Special anatomical, physiological
or behavioral adaptations:
The pufferfishes are unique in that they are able to inflate predators, making them at least twice as big. They do this by sucking in and retaining water or air in their bodies. Puffers have a pair of sharp front teeth which resemble a parrot's beak, and enable them to crush the shellfish and crabs they usually feed on. Pufferfishes themselves should not be eaten for they often contain a virulent toxin in their tissues.

Comments about the Green Puffer of the Fort Worth Zoo:      



Usually seen at aquarium when they are small, they can grow to 4-6 inches and do some serious damage to most fish. Therefore, these fish should be keep in small groups. The female lays a clutch of 150-200 eggs onto a flat surface and the male guards them until hatched. 

Data and results

Salinity in sea water:

35g in 1000ml(measured by a salinity meter used in fish shop)
Calculation:

*total amount of salt added / total amount of water *100%=percentage of salinity of sea water.


  • The percentage of the salinity of the world’s seawater is 3.5%


# percentage of salinity of water/percentage of salinity in sea water *100%= concentration of salinity in the freshwater when compared with sea water.
For Golden tiger barb

Table showing the salinity of the water

Date

Volume of water(ml)

Amount of salt added (g)

Total amount of salt in water (g)

Percentage of salinity of water (%)*

6.11.2006

3000

0

0

0

7.11.2006

3000

8.25

8.25

0.275

9.11.2006

3000

8.25

16.5

0.55

13.11.2006

4000

16.5

33

0.825

20.11.2006

3000

8.25

33

1.1

22.11.2006

3000

8.25

41.25

1.375

24.11.2006

3000

8.25

49.5

1.65


Table showing any changes in the behavior of fishes in saline solution of different concentration

Date

Changes in fishes

7.11.2006

3 fises are take part in the experiment.

They are healthy and swim very quickly



8.11.2006

The color of their back turns brick red

9.11.2006

Same as before

10.11.2006

Same as before

13.11.2006

The water was changed. Same as before. Another small fish was added ,water was changed

14.11.2006

The 3 old fishes were the same as before. The color of the small fish’s back turns brick red, and swam quickly.

15.11.2006

Same as before

20.11.2006

The water was changed, fishes were healthy although no food supply for 4 days (holidays).

21.11.2006

Same as before

22.11.2006

Same as before

23.11.2006

3 big fishes were healthy; the small fish did not eat.

24.11.2006

3 big fishes were healthy; the small fish did not eat.

25.11.2006

3 big fishes were healthy; the small fish died, the area near its gill turned from golden yellow to red.

27.11.2006

3 big fishes died as well.


Table showing no. of survival date and concentration of salinity

Date

concentration of salinity in the freshwater when compared with sea water.(%)#

Number of accumulated survival date

Number of fish present

6.11.2006

0

0

3 elder fish

7.11.2006

(0.275/3.5*100%)7.86

1

3 elder fish

9.11.2006

15.71

3

3 elder fish

13.11.2006

23.57

7

3 elder fish+1 younger fish

20.11.2006

31.43

14

3 elder fish+1 younger fish

22.11.2006

39.29

16

3 elder fish+1 younger fish

24.11.2006

47.14

18

3 elder fish+1 younger fish

25.11.2006

47.14

19

3 elder fish

27.11.2006

47.14

21

0

After all the fishes died, we disectd the 3 big fishes. We find out that one of the fishes is a female because we find some eggs inside its abdominal cavity. One of the fishes is a male because no eggs were there. However, the eyes of one of the fishes turned milky and some yellow mucus was flowed out of its mouth and it smelled nasty. Also, its abdominal cavity becomes brown in color, it was hard to distinguish the structure of its tissues.



Table showing the salinity of the water

Date

Volume of water(ml)

Amount of salt added (g)

Total amount of salt in water (g)

Percentage of salinity of water (%)

20.11.2006

2000

0

0

0

21.11.2006

2000

16.5

16.5

0.825

22.11.2006

2000

16.5

33

1.65

24.11.2006

2000

5.5

38.5

1.925

7.12.2006

2000

5.5

44

2.2

11.12.2006

2000

5.5

49.5

2.475

13.12.2006

2000

5.5

55

2.75

14.12.2006

2000

5.5

60.5

3.025

18.12.2006

2000

5.5

66

3.3

20.12.2006

2000

5.5

71.5

3.575


Table showing any changes in the behavior of fishes in saline solution of different concentration.

Date

Changes in fishes

20.11.2006

4puffer fishes took place in this experiment

21.11.2006

4 puffer fishes were healthy

22.11.2006

Same as before

23.11.2006

The eyes of one of the puffer fishes became milky, the tails of three of the puffer fishes are beaten off by the biggest puffer fish

.24.11.2006

2 puffer fishes were eaten by the biggest one.

27.11.2006

The remaining 2 fishes still alive, but the fin of one of the fish was eaten by the biggest one.

28.11.2006

All the fins of the wounded fish were beaten, so it cannot balance its body, it was thrown to the rubbish bin. The fish was fed with brine shrimp.

6.12.2006

The last puffer fish was healthy.

7.12.2006

Same as before. Water was changed .

11.12.2006

The last puffer fish was healthy.

12.12.2006

Same as before. Water was changed

13.12.2006

The last puffer fish was healthy.

14.12.2006

The last puffer fish was healthy.

15.12.2006

Same as before. Water was changed

18.12.2006

The last puffer fish was healthy.

19.12.2006

The last puffer fish was healthy.

20.12.2006

Same as before. Water was changed

2.1.2007

The fish was died and the reason is unknown.


Table showing no. of survival date and concentration of salinity


Date

Concentration of salinity in the freshwater when compared with sea water.(%)#

Number of accumulated survival date

Number of fish present

20.11.2006

0

0

4 puffer fishes

21.11.2006

23.57

1

4 puffer fishes

22.11.2006

47.14

2

4 puffer fishes

23.11.2006

47.14

3

4 puffer fishes

24.11.2006

55.00

4

2 puffer fishes

27.11.2006

55.00

7

2 puffer fishes

28.11.2006

55.00

8

1 puffer fish

7.12.2006

62.86

17

1 puffer fish

11.12.2006

70.71

21

1 puffer fish

13.12.2006

78.57

23

1 puffer fish

14.12.2006

86.43

24

1 puffer fish

15.12.2006

86.43

25

1 puffer fish

18.12.2006

94.29

28

1 puffer fish

19.12.2006

94.29

29

1 puffer fish

20.12.2006

102.14

30

1 puffer fish

2.1.2007

102.14

43

0


Analysis of the results:

(Background information:

Osmoregulatory mechanism



Fresh water fish live in water with little or no salinity. However, their internal salinity (body fluid) is 0.9%—just like ours. To complicate matters, a fish must exchange water with its environment for respiration and nutrition through its gills and its digestive tract, so it needs a mechanism to prevent its internal salinity from being lost through its gills and gut to the low concentration in the pond, and correspondingly gaining water. Fish accomplish this by a mechanism called osmoregulation. One of the main guardians of salinity is the kidney. As lots of water enter through gills and gut, the kidney retains the salt and produces huge amounts of very dilute urine.
Differences in osmoregulatory mechanism between freshwater fishes and marine fishes:

Freshwater fish (teleosts) .Their body fluids (1/3 the concentration of sea water) have a greater concentration than their surrounding environment (hyperosmotic). As a result they are constantly taking on water by diffusion through their skin and, to a much larger extent, through the thin membranes of their gills. Therefore, to maintain the high concentration of their body fluids, they must continuously excrete the excess water they have absorbed. This is accomplished by highly efficient kidneys which produce a very dilute urine (Moyle and Cech, 1982). The only problem with such a high rate of urine production is that a loss of salts and other solutes is unavoidable. Salts, mostly Na+ and Cl-, are also lost by diffusion through gill membranes. Some of these can be replaced by ions contained in food but by far the most common method is through the movement of a substance against an osmotic gradient through the use of energy. This usually involves the exchange of one substance for another. In the case of freshwater fish, Na+ ions are taken from the water and ammonia ions are taken from the fish and they are exchanged. This effectively rids the fish of ammonia. Chloride ions are exchanged for carbonate ions which helps in maintaining the pH of the body fluids.
Marine fish (teleosts) .Their body fluids are, again, 1/3 of that of sea water but this time they are in sea water so their body fluids are hypoosmotic to their environment. As a result they will tend to lose water by osmosis to the environment through their skin but mostly through their gills. Consequently, they have developed mechanisms and behaviour to compensate for this water loss. Firstly, the kidneys of marine teleosts are modified in such a way that very little water is extracted from the blood, some species even lack certain kidney structures and can't eliminate water (Gordon, 1977; Moyle and Cech, 1982). This results in a reduction in the loss of water by the production of urine. However, water is still being lost by the gills and this cannot be stopped, so the only method left is to somehow replace the water as quickly as it is lost. Marine teleosts accomplish this by actually drinking water, the most reliable drinking rates reported in the literature range from 3-10 ml/(kg hr) (Gordon, 1977). However, drinking water by itself cannot solve the problem, a complex series of events must first occur in the digestive tract. These events are not yet well understood but it is known that most of the water is absorbed as are the monovalent ions Na+ and Cl- (they are, after all, drinking salt water!), while the divalent ions (such as magnesium and sulfates) are excreted by the kidneys (Gordon, 1977). Sodium (Na+) and chloride (Cl-) also move by diffusion into the body through the gills. Therefore, Na+ and Cl- ions will accumulate in the body of the fish and must be eliminated, this is accomplished by special cells in the gills called chloride cells, which me these ions out of the body by active transport
Golden Tiger Barbs do not require any special attention and are rather hardy. They need their water to be between 68 and 79 degrees Fahrenheit. Golden Tiger Barbs do best in slightly acidic water, with a pH in the range of six to seven.)
In this experiment, the small golden tiger barb live for 11 days and then die.The actual reason is unknown,but it didn’t eat for a few days.We guessed it couldn’t adapt to the change in environment,i.e.change in salinity in water, so it became ill and finally died.After the small fish died,the other 3 golden tiger barbs died and they had lived for 21 days.They died suddenly because they were still healthy on 25.11.2006,maybe the small fish got illness and inflect the other fishes.

The osmoregulatory mechanism in freshwater fish is to absorb water continuously from water to dilute their body fluid.However, as the salinity in the experimental fish tank increases, the concentration of mineral salts in the water is higher than that in their body, so water will diffuse out from their body.Since it is the opposite way of osmoregulation in their body,i.e. initailly,they absorb water but now,they lose water,so their body may not br adaptable to the change and affect their health.Marine fishes have the osmoregulatory mechanism to compensate the loss of water from their body while freshwater fishes do not, so freshwater fishes cannot live in sea water.

For Pufferfish,they often sold as freshwater fish, but this species actually thrives in brackish water and may even requires saltwater when reaches adulthood. Therefore, the puffer fish can live for 43 days in this experiment, which is much more than that of the golden tiger barb. Initially ,4 puffer fishes are introduced in the experiment, but as time passed,the stronger fish eat the other fishes.This is because puffer fish is very aggressive and they eat meat,so they will kill each others.One thing special is that the strongest puffer fish only beat off the fins of the other fishes,but not their body.We guess this is due to the presence of toxins in puffer fish.On the 43 days,the strongest fish died,we don’t know the reason, and as we left the fish in the laboratory in Christmas holiday(13 days),we don’t know the actual time when the fish died.The reason for the puffer to die maybe lack of food.As the fish didn’t die when the concentration of salinity in water is 94.29%,we guess it will not die if the concentration increased to 102.14%.

However, in this experiment,only one type of freshwater fish is analysed and after the fishes died,we didn’t carry out the same experiment again.Therefore,the data is not reliable.We should carry out the experiment for a few times and use different types of fishes in the experiment.

Conclusion for the first part of the experiment:

Freshwater fishes cannot live in sea water because freshwater fishes do not have the osmoregulatory mechanism to absorb water to compensate the loss of water into the environment.However, it will not die suddenly, it will get sick and refuse to eat and finally die.

Topic : The Dissection of two fishes
Aim

The objective of the experiment is to compare the kinds of food obtained by them by extracting the substances in the stomach and comparing the appearance of their stomach.


The details of the two fishes

There are two fishes included in the experiment. They are perch(鱸魚) and crucian crap(鯽魚) respectively.




Perch(鱸魚)

Labrax japonicus
Morthology:

Perch have "rough" or ctenoid scales.. On the dorsal side of the fish, there consists a upper maxilla and lower mandible for the mouth, a pair of nostrils, and two lidless eyes. On the posterior sides are the operculum, which are used to protect the gills. They have a pair of pectoral and pelvic fins. On the anterior end of the fish, there are two dorsal fins. The first one is spiny and the second is soft. There is also an anal fin, which is also considered spiny, and a caudal fin. Also there is a cloacal opening right behind the anal fin.




Crucian crap(鯽魚)

Carassius carassius

The crucian is a medium-sized cyprinid, which rarely exceeds a weight of over 3.3 pounds (1.5 kg). They usually have a dark green back, golden sides, and reddish fins, although other colour variations exist.


Results

The table showing the difference between the two fishes






Perch

Crucian crap

The size of body(cm)

26.7

25.9

Presence of teeth

present

Absent

The lenght of stomach(cm)

5.1

2.6

The shape of stomach

The stomach of the perch is larger and its thickness is more than the that of its intestine. Thus it is easy to distingish the stomach and intestine.

The stomach of the crap is slightly conical and its shape is similar to its intestine. As the shape of them are similar, it is difficult to recognise the stomach.

The substance in the stomach

nothing

nothing

The length of intestine

29.0

37.5

The positon of mouth

anterior mouths

inferior mouths


The analysis of the result

Unfortunately, there is nothing can be found in the stomach of both fishes. The fishes used in the dissection were bought from market, so the fishes may be starved for few days before we bought them and the food obtained were digested and absorbed.


However, the difference between the size of their stomach can be seen easily.

1. By the presence of teeth and the lenght of intestine, we can know which type of fish are they. (Carnivorous fishes, herbivorous fishes and omnivorous fishes)

In order to digest and absorb the food efficiently, the intestines of different fish which feed on different kinds of food developed to its optimum shape during the evolution. For example herbivores have long intestine and the stomach are short(some the herbivorous fishes do not have stomach), it can lengthen the time of plant food stay in the digestive system as the food is difficult to digest. Omnivorous or meat-eating fish have much shorter intestines and larger stomach, which can suit to their easily digested diet which is rich in protein.



The intestines run in several coils through the body. The intestines of meat-eating fish are short and straight, whereas those of plant-eating fish are long and twisting.
As the food resource of herbivorous fishes can be the aqueous plants or algae which can be ingested without chewing, the presence of teeth is not important of them. Oppositely, the carnivorous fishes have to chew the solid food(e.g. smaller fishes),they must have a set of teeth.

2. By the position of mouth, we can also know that the habitats of the fishes

Fish with anterior mouths have horizontal mouths pointing forwards and a body equally curved at the top and bottom (it is perch in this experiment). These fish live in the middle water levels and feed there.

Fish with inferior mouths(it is crucian crap in this experiment) usually have bearded mouths, sloping downwards and a body which curves upwards, with a relatively flat belly line (e.g. armoured catfish, loaches). These fish feed on the floor, searching for the food in the deeper sea



There are many intermediate forms between superior fishes and anterior fishes. Fish from the middle water levels will look for food on the surface of the water and surface fish will look at lower levels. However, ground feeding fish(fishes with interior mouths) are reluctant to leave their "realm" to look for food in open water.

The conclusion of this part of the experiment

Although we could not compare the food eaten by the perch and the crucian crap, by the presence of teeth, the characteristics of their digestive systems, the position of the mouth, we know that perch is carnivorous fish and live near the surface of the water and crucian crap is herbivorous fish and live in the deeper of the water.


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