Atlantic Bluefin Tuna Population - Revision history

Vokp00: /* Model */

2020-01-20T19:27:32Z

‎Model

Vokp00: /* Conclusion */

2020-01-20T19:25:03Z

‎Conclusion

Vokp00: /* Results */

2020-01-20T19:03:37Z

‎Results

Vokp00: /* Whole population point of view */

2020-01-20T18:42:58Z

‎Whole population point of view

Vokp00: /* Historical catches */

2020-01-20T18:25:57Z

‎Historical catches

Vokp00: /* Historical catches */

2020-01-20T18:25:45Z

‎Historical catches

Vokp00: /* Method */

2020-01-20T18:25:10Z

‎Method

Vokp00: /* Method */

2020-01-20T18:21:40Z

‎Method

Vokp00: /* Model */

2020-01-20T18:19:30Z

‎Model

Vokp00: /* Model */

2020-01-20T18:18:05Z

‎Model

@@ Line 126: / Line 126: @@
 = Model =
-Two points of view were taken regarding the BFT population. One was focused on the adults and juveniles separately, the other was taking account the population as a whole.
+Two points of view were taken regarding the BFT population. One was focused on the adults and juveniles separately, the other was taking account the population as a whole. Both models can be found [[http://www.simulace.info/index.php/File:BFTmodels.zip]].
 == Emphasis on adults and juveniles ==

← Older revision		Revision as of 19:25, 20 January 2020
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	=Conclusion=		=Conclusion=
		+	In conclusion, the BFT population is not in a healthy state. Most of the individuals are too young to reproduce and to make matters worse, juveniles are often caught by fishing boats, so they do not grown into adults to reproduce. Therefore, measures should be taken to prevent overfishing of the younger fish in order to provide a solid base for tuna reproduction in the future. The instilled quota are definately the way to go to preserve the remains of the species, yet the problem of illegal tuna fishing should be addressed. Unfortunately, the black market with BFT will continue unless the demand for tuna meat will drop. So the fate of BFT is also partly in the hands (or stomachs) of the consumers, who decide whether they will demand more delicious tuna meat for sushi and other dishes, in order to help preserve this graceful and swift species. Another aspect, is of course, the tuna fishing lobby, that is trying to keep the tuna quota as high as possible, ignoring the advice of scientists to lower quota quite dramatically, but that is still in correlation with the profit obtained from selling tuna meat.

	=Citations=		=Citations=

← Older revision		Revision as of 19:03, 20 January 2020
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	=Results=		=Results=
		+	The results have varied very strongly depending on the starting number of 1) juvenile population or 2) the selected population as a whole. Due to the fact, that the BFT population is marked as unknown in size in most sources a different tool might be more beneficial for this task. This might include the usage of random forests (as they were already used as a solution to the problem of biomass and mortality indexes [4]). Or perhaps the use of Monte Carlo for the initial starting points, yet there might be the issue of getting to the right data, because most BFT data are focused on the numbers of BFT caught and other statistics map only a selective part of the population, usually to provide scientific data about the behaviour, size and weight based information about the wild BFT stocks.

	=Conclusion=		=Conclusion=

← Older revision		Revision as of 18:42, 20 January 2020
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	== Whole population point of view ==		== Whole population point of view ==
		+	<math>BFTsSpawned = EggsLaid/1000</math>
		+
		+	<math>EggsLaid = SpawnableStock*(randomly chosen, 5 - 45 million)</math>
		+
		+	<math>SpawnableStock = AdultBFTs/2</math>
		+
		+	<math>AdultBFTs = BFTpopulation0.220.4</math>
		+
		+	<math>BFTpopulation = BFTsSpawned*12 - DeadBFTs</math>
		+
		+	<math>DeadBFTs = AdultMortality + Fishing + Juvenile Mortality + IllegalCatches</math>
		+
		+	<math>Quota = 36000(variable)</math>
		+
		+	<math>Fishing = Quota</math>
		+
		+	<math>Illegal catches=Quota*(random 0.3 - 1.5 coefficient)</math>
		+
		+	<math>Adult Mortality = AdultBFTs*0.1</math>
		+
		+	<math>JuvenileMortality = BFTsSpawned12(randomly chosen 0.29 - 0.41 coefficient)</math>
		+
		+	Vensim model focusing on the BFT population as a whole.
		+
		+	[[File:populationPOV.png]]

	=Results=		=Results=

@@ Line 115: / Line 115: @@
 <b>Image 7.</b> Tuna quota set by ICCAT for each state fishing in the Western Atlantic and the Mediterranean [14].
-=== Historical catches ===
+=== Historical catches vs weather ===
 To provide some insight on the topic of human-unrelated tuna stock changes happening in cycles, an image of the last 400 years tuna catch records is presented next to a graph with the temperature fluctuations, especially during the so-called little ice age. On one hand, it appears, that the temperature changes and number tuna catches are correlated. On the other it might be nothing but a conincidence.

@@ Line 120: / Line 120: @@
 [[File:historicaltunacatches.png]][[File:littleiceage.png]]
-<b>Images 8 and 9.</b> Historical tuna catches. From the bold line, it is apparent, that the catches fluctuate in very similar about 110 years intervals. Therefore the hypotheses is presented, that the tuna stock is independent on human fishing exploitation [6] and [5]. The second image shows worldwide temperature changes, avilable [https://skepticalscience.com/coming-out-of-little-ice-age.htm here].
+<b>Image 8 and 9.</b> Historical tuna catches. From the bold line, it is apparent, that the catches fluctuate in very similar about 110 years intervals. Therefore the hypotheses is presented, that the tuna stock is independent on human fishing exploitation [6] and [5]. The second image shows worldwide temperature changes, avilable [https://skepticalscience.com/coming-out-of-little-ice-age.htm here].
 == Model creation ==

@@ Line 12: / Line 12: @@
 =Method=
 == Research ==
 As a first step, an extensive research was conducted to gather the most relevant papers, articles and other sources, concerning BFT population, farming, quotas, statistics, environment and fishing.

← Older revision		Revision as of 18:21, 20 January 2020
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	<b>Images 8 and 9.</b> Historical tuna catches. From the bold line, it is apparent, that the catches fluctuate in very similar about 110 years intervals. Therefore the hypotheses is presented, that the tuna stock is independent on human fishing exploitation [6] and [5]. The second image shows worldwide temperature changes, avilable [https://skepticalscience.com/coming-out-of-little-ice-age.htm here].		<b>Images 8 and 9.</b> Historical tuna catches. From the bold line, it is apparent, that the catches fluctuate in very similar about 110 years intervals. Therefore the hypotheses is presented, that the tuna stock is independent on human fishing exploitation [6] and [5]. The second image shows worldwide temperature changes, avilable [https://skepticalscience.com/coming-out-of-little-ice-age.htm here].

		+	== Model creation ==
		+	After the research and data collection, a model was put together in the programme Vensim based on the data and research findings.

	= Model =		= Model =

@@ Line 119: / Line 119: @@
 = Model =
 == Emphasis on adults and juveniles ==
 The following equations were used in the model:
@@ Line 164: / Line 166: @@
 Stock and flow diagram model created in Vensim for the adult and juveniles point of view.
 [[File:adultsandjuveniles.png]]
 =Results=

@@ Line 119: / Line 119: @@
 = Model =
 The following equations were used in the model:
@@ Line 127: / Line 128: @@
 Spawning adults are calculated as 22 % of the population (the most recent data available), divided by 2 (according to research, BFT spawns every 2 to 3 years) and a coefficient of 0.4 was added to mimic the female population (due to higher mortality, there is less females than males). The number of eggs is not in millions but in thousands to not need to divide the result by 1000 to provide juvenile weight in metric tonnes (a young juvenile starts at around th weight of 1 kg).
-<math> Juveniles = Spawning * 12 </math>
+<math> Juveniles = (Spawning - Growth) * 12 </math>
 Juveniles is the nmber of spawned times 12 (that is the amount of kgs grown in the first year of life).
@@ Line 137: / Line 138: @@
 <math>Adults = Growth - Deaths</math>
-<math>Death = (Adult Mortality * Adults) + Legal Fishing + Illegal Fishing</math>
+<math>Deaths = (Adult Mortality * Adults) + Legal Fishing + Illegal Fishing</math>
 Adult mortality is set at 0.1 according to research.
@@ Line 152: / Line 153: @@
 Coefficient is randomly chosen based on numbers from research.
 =Results=