Marine aquaculture — Paper 4 · A Level Marine Science 9693

3 (a) Explain how dredging affects water quality, productivity and food webs in marine environments. … … … … … … … … … … … … … … … … … … [7] (b) Explain the possible ecological consequences of using marine antifouling paints. … … … … … … … … … … [3] (c) Genetically engineered fish have recently been produced that contain a fluorescence gene from jellyfish. The fish fluoresce, glowing green, when under conditions of environmental stress such as the presence of pollution. (i) State the meaning of the following terms. genetic engineering … … selective breeding … … [2] (ii) Suggest benefits and risks of using these fish as indicators of pollution. … … … … … … … [3] [Total: 15]

15 marks

Mark scheme: 3(a) water quality- at least 1 of: (a) stirring up silt / substrate / sediment / sand / mud OR increases turbidity (b) idea of, reduces light penetration / AW ; (c) silt damaging gills ; (d) release of, toxins / heavy metals, from substrate ; (e) nutrient release can cause, algal blooms / eutrophication / description of ; productivity & food webs – max 6 of: (f) reduced photosynthesis ; (g) less primary productivity ; (h) loss of, food / energy, for primary consumers / herbivores ; (i) damaging, habitats / seabed / substrate / coral / reef ; (j) (toxins / heavy metals / chemicals) bioaccumulate / description of ; (k) difficult for predators to see prey ORA / affects on breeding ; (l) increased food for / benefits, (some) filter feeders / shellfish ; 7 I seabed unqualified A idea of, silt / AW damages coral polyp A named toxins – not antifouling paint ; I reduced oxygen unqualified A nutrient release from sediment causes increase in productivity Productivity needs to be in context of producers or plants or less photosynthesis. I productivity unqualified e.g. can’t find mates, damage to gametes / larvae Question Answer Marks Guidance 3(b) any 3 of: (Antifouling paint contains) TBT / mercury / copper / lead / heavy metals bioaccumulation / biomagnification / not broken down / pass along food chains / AW ; ref. to, sex reversal of molluscs / imposex in molluscs / sterility in molluscs / interferes with sex ratio in molluscs ; idea of, (resulting in) less food for later trophic level ; 3 A marine named examples of molluscs 3(c)(i) (Genetic engineering) changing of the, genetic material / DNA / genes / alleles, of an organism ; (Selective breeding) (humans choose) individuals (of same species) mated for specific characteristics / alleles / traits ; 2 Individuals are selected for a particular feature to breed 3(c)(ii) benefits-at least 1 of: cheap method (for detecting pollution) ; quick / in-situ method ; can be used by unskilled operator / little training needed ; risks-at least 1 of: escape / get into the wild ; breed with native species / transfer gene into wild populations ; any other qualified risk escape / getting into the wild, e.g. food chain effect / competition ; 3

This question in 9693/41 May/June 2017

4 (a) Many areas of coastline in tropical countries are experiencing increased tourism. Discuss the conflicts of interest that could arise between the stakeholders of an existing fishing industry and a developing tourist industry on a region of tropical island coastline. … … … … … … … … … … … … … … … … … [6] (b) (i) Aquaculture is being increasingly used as a method of conserving commercial fish stocks. Describe and explain the requirements of a successful, sustainable aquaculture venture. … … … … … … … … … … … … [5] (ii) Discuss the advantages and disadvantages of the introduction of cultivated fish into wild populations. … … … … … … … … … … … … [4]

15 marks

Mark scheme: 4(a) negative conflict of tourism on fishing- at least 1 of: (a) loss / damage to fishing areas / reefs / habitats / beaches ; (b) loss of nursery / spawning grounds ; (c) reduced fish population / reduced catch ; (d) damage to nets / fishing gear ; (e) loss of fishing areas, due to bans / protected zones / conservation zones ; (f) idea of, (more) pollution / litter / sewage ; (g) tourist industry takes employment / not enough people to enter fishing / conflict of employment ; (h) idea of, tourism raises cost of living for fishermen / prices rise / inflation / loss of housing / AW ; (i) reduced income (from fishing) ; (j) loss of harbour space ; (k) fishing boats conflict with tourist boats for space ; 6 To award full marks, at least one mark should be from each section I environment I noise pollution and light pollution award income mark once only award boat conflict mark once only Question Answer Marks Guidance negative conflict of fishing on tourism – at least 1 of: (l) idea of, fisheries are unsightly ; (m) fishing boats conflict with tourist boats for space ; (n) fishing (boats) may endanger tourists ; (1) fishing may deplete fish / coral / habitat, that attract tourists ; (2) reduced income (from tourism) ; A unpleasant smell award boat conflict mark once only award income mark once only Question Answer Marks Guidance 4(b) (i) any 5 of: (a) availability of stock / adults for spawning / brood stock ; (b) (so that) fish are not taken from wild / not depleting wild stocks ; (c) availability of food (stocks) ; (d) that is not from wild / e.g. uses fish waste / trimmings / AW ; (e) water purification systems / clean water / low stocking density / don’t over feed ; (f) to reduce, pollution / disease spread / for disease management / prevent eutrophication ; (g) minimise use of, antibiotics / pesticides ; (h) to prevent development of resistance ; (i) available labour force / AW ; (j) availability of location OR suitable location that does not destroy habitats / mangroves ; (k) transport access / roads / rail, for supplies in and / or products out ; (l) sufficient profit potential / idea of, economic benefit / AW ; (m) (due to) market demand / access to export market / suitable exchange rates ; 5 Question Answer Marks Guidance 4(b) (ii) advantage- at least 1 of: (a) rehabilitation of depleted stocks / replenishing populations / AW ; (b) restoring food webs / ecological balance ; disadvantage- at least 1 of: (c) (however) genetically weak stocks / weakens gene pool / inbred fish / poor genetic diversity / deleterious alleles transfer to wild ; (d) cultivated stocks are not well adapted / are weaker / susceptible to predators / AW ; (e) spread disease / parasite transfer ; (f) over-population / over-predation / damage to food chains / idea of, competition ; 4 To award full marks, at least one mark should be from each section (i.e. at least one advantage and one disadvantage) A named examples of diseases / parasites

This question in 9693/41 May/June 2017

3 (a) (i) Explain why the precautionary principle is used when considering whether to permit the aquaculture of genetically engineered fish such as salmon. … … … … … [2] (ii) Outline how and why salmon have been genetically engineered for aquaculture. … … … … … … … … … … … [5] (b) Both genetically engineered and non-genetically engineered salmon are grown using aquaculture systems. Explain the negative impacts that aquaculture could have on wild fish near to a salmon farm. … … … … … … … … … … … … … … … … … [8] [Total: 15]

15 marks

This question in 9693/40 May/June 2018

4 Wild populations of giant clams have decreased since the 1990s. Giant clams are now raised by aquaculture in some Pacific Islands for food, and to help in conservation efforts by releasing cultivated clams into the wild. (a) State what is meant by the term conservation. … … … [1] (b) (i) Outline the process used for the aquaculture of giant clams. … … … … … … … … … … … … … [5] (ii) Explain the risks associated with releasing cultivated giant clams into the wild. … … … … … … … … … … [4] (c) Giant clams are osmoconformers. Explain the meaning of the term osmoconformer and explain the effects on the clams of being placed in water of very high and very low salinities. … … … … … … … … … … … … … … [5]

15 marks

This question in 9693/40 Oct/Nov 2018

4 Human activity is threatening the marine environment in many ways. Conservation is becoming increasingly important. (a) Explain the meaning of the term conservation. … … … … [2] (b) Artificial reefs and the release of cultivated stocks are two methods of rehabilitating depleted fish stocks. Compare the advantages and disadvantages of these methods. … … … … … … … … … … … … … [6] (c) Explain how ecotourism practices can reduce damage to the marine environment. … … … … … … … … … … … … … … … [7] [Total: 15]

15 marks

Mark scheme: 4(a) protecting / preserving / restoring, species / habitats / biodiversity / food webs / food chains ; preventing extinction / idea of: there for future generations ; 2 I environment I protecting animals 4(b) any 6 of: (a) (artificial reefs) act as, nursery ground / shelter / habitat ; (b) idea of: (artificial reefs) allow development of, food, chains / webs or community OR (artificial reefs) increase biodiversity (of the area) ; (c) (artificial reefs) reduce coastal erosion ; (d) release of toxins / pollution from, wrecks (used to make reefs) / reefs ; (e) (artificial reef) may, damage sea bed / create obstacles ; (f) (artificial reefs) are a, long-term / sustainable, solution ; (g) (artificial reefs) take a long time to establish ; 6 A acts as a substrate for / allows coral growth Question Answer Marks Guidance 4(b) (h) (artificial reefs) provide revenue from diving / tourism OR (cultivated stocks) provide revenue from increased fishing / tourist (fishing) ; (i) (cultivated stocks) may change, gene pool / genetics of population / alters alleles (of wild population); (j) (cultivated stocks) may have infections / disease ; (k) idea of: (cultured stocks) are not adapted correctly OR idea of: (cultured stock) outcompete wild fish ; A descriptions of poorly adapted A any idea of competition I costs 4(c) any 7 of: Carbon neutral idea (a) distinct method to reduce carbon footprints ; (b) to reduce use of fossil fuels / less carbon (dioxide) emissions / lower carbon footprint / carbon sequestration ; (c) reduced, global warming / climate change / less ocean acidification / less (coral) bleaching ; reduction of habitat / species damage (d) not using coral / careful selection of site (avoid nesting beaches etc) / restricting access / careful anchorages / responsible diving or excursions / not removing species for curios / avoiding light or noise pollution ; Waste (e) (rubbish) recycling / litter removal or disposal / stop use of plastic / use plastic alternatives / encourage tourists to remove litter / encourage taking litter home ; (f) less, (micro) plastic / toxins, entering food chains OR less negative effects of litter on marine species ; (g) sewage disposal or treatment / run-off disposal / restrict , detergents / fertiliser / chemicals, use ; (h) less, eutrophication / algal blooms / red tides / toxic waste (in sea) ; 7 e.g. renewable energy sources / minimising vehicles / reduction in food miles Question Answer Marks Guidance 4(c) Water (i) recycling of water / use of grey water / water treatment ; (j) less need for desalination / protection of estuaries ; Money (k) sponsorship of conservation projects / money from tourism is used to maintain species diversity / local people employed / money into local economy ; Education (l) tourists / locals, gain better understanding about, (marine) conservation / (marine) environment / (marine) issues / stated marine issues ; Food (m) idea of: sustainable food sources / reducing, overfishing / excess agriculture / local food sources / seasonal food sources ; I not eating fish

This question in 9693/41 May/June 2019

2 An investigation was carried out to measure the effect of adding shrimp to aquaculture tanks of tilapia fish. Tilapia were placed into tanks and grown with shrimp added at different population densities. The yields of tilapia and shrimp were then determined. The results are shown in Table 2.1. Table 2.1 yield / g m–2 combination of species shrimp tilapia tilapia alone – 483.5 tilapia and low-density shrimp 23.3 499.2 tilapia and medium-density shrimp 30.6 455.8 tilapia and high-density shrimp 61.1 401.6 (a) (i) Calculate the percentage change in yield between tilapia grown alone and with shrimp at high density. Show your working. … [2] (ii) Describe the effect of using different population densities of shrimp on the yield of tilapia. … … … … [2] (iii) Suggest two variables that should be controlled in this investigation. 1 … 2 … [1] (b) Shrimp feed on waste food and the wastes produced by tilapia. Suggest the benefits of growing tilapia with shrimp rather than growing tilapia alone. … … … … … … [3] [Total: 8]

8 marks

This question in 9693/40 Oct/Nov 2019

4 (a) With reference to named examples, explain the advantages of internal fertilisation compared to external fertilisation. … … … … … … [3] (b) Oysters use external fertilisation. Outline the life cycle of oysters. … … … … … … … … … … … [4] (c) Oysters are often grown by aquaculture businesses. Discuss how a new aquaculture business could affect other industries in a coastal community. … … … … … … … … … … … … … … … … [8] [Total: 15]

15 marks

This question in 9693/40 Oct/Nov 2019

1 Scientists genetically engineered zebrafish for rapid growth. They inserted an additional growth hormone gene into the DNA of zebrafish eggs. The growth hormone gene was injected into 366 zebrafish eggs. 273 of these eggs survived, but only 2 of these eventually developed into genetically engineered fish with the growth hormone gene switched on. (a) (i) Calculate the percentage of injected eggs that developed into genetically engineered zebrafish with the growth hormone gene switched on. … [1] (ii) Only 2 of the 273 zebrafish were successfully genetically engineered and showed rapid growth. Suggest why the success rate of genetic engineering is so low. … … [1] (b) The scientists carried out an experiment to investigate whether the genetically engineered zebrafish grew faster than non-genetically engineered zebrafish. They produced large numbers of genetically engineered zebrafish and calculated their mean mass every week from 4 weeks until 10 weeks. This experiment was repeated with non-genetically engineered zebrafish. The results of the experiment are shown in Table 1.1. Table 1.1 mean mass of zebrafish / g age of zebrafish / weeks genetically engineered non-genetically engineered 4 0.12 0.12 5 0.18 0.15 6 0.21 0.18 7 0.28 0.22 8 0.31 0.25 9 0.33 0.28 10 0.34 0.30 (i) Plot a graph to show the growth of both groups of zebrafish from 4 weeks to 10 weeks. Join your points with ruled, straight lines. [5] (ii) Compare the growth rates of the non-genetically engineered and genetically engineered zebrafish. … … … … [2] (c) Salmon produced by aquaculture are often fed with pellets made from wild fish such as anchovies and herring. Genetically engineered salmon have recently been produced that convert food into growth very efficiently. (i) 1000 kg of wild fish are required to make 250 kg of pellets. 5000 kg of wild fish are required to make the pellets to produce 1000 kg of non-genetically engineered salmon. 1125 kg of pellets are required to produce 1000 kg of genetically engineered salmon. Calculate the difference in the mass of wild fish used to produce 1000 kg of non-genetically engineered salmon compared to 1000 kg of genetically engineered salmon. … kg [1] (ii) Suggest and explain the environmental benefits of using the genetically engineered salmon. … … … … … … [3] [Total: 13]

13 marks

This question in 9693/40 May/June 2020

3 (a) Outline how the techniques of intensive aquaculture differ from those of extensive aquaculture. … … … … … … … … [4] (b) Describe the process used for the aquaculture of shrimp. … … … … … … … … … … [5] (c) Fig. 3.1 shows an aquaculture method called integrated multitrophic level aquaculture. filter feeders such as mussels and scallops that feed on small particles of waste seaweeds that remove nitrates and phosphates and photosynthesise current lobster, crabs and sea cucumbers that feed on waste particles Fig. 3.1 Discuss how this method of aquaculture meets the requirements of sustainable aquaculture and minimises its impacts on the environment. … … … … … … … … … … … … [6] [Total: 15]

15 marks

This question in 9693/40 May/June 2020

4 (a) (i) Outline how salmon have been genetically engineered for rapid growth. … … … … … … [3] (ii) Genetically engineered salmon are grown in aquaculture systems. Explain how a new aquaculture venture could affect the tourist industry in a coastal area. … … … … … … … … … … … … [6] (b) Discuss the evidence that emissions of carbon dioxide and other greenhouse gases from human activities are causing global warming. … … … … … … … … … … … … [6] [Total: 15]

15 marks

This question in 9693/40 Oct/Nov 2020

4 Aquaculture is used to produce large quantities of seafood. (a) Describe how salmon are grown to maturity in sea cages, using extensive aquaculture. … … … … … … … … [4] (b) Table 4.1 shows the estimated environmental impacts of aquaculture of different species. Biotic depletion is a measure of the mass of wild organisms that are lost due to the aquaculture method. Table 4.1 relative environmental impact per 1000 kg of product species biotic phosphate released CO2 released land loss / km2 depletion into ocean / kg / kg / kg mussels –20 2000 0.10 10 salmon 70 100 100 2100 shrimp 80 15 000 1500 1000 seaweed –70 –150 0.15 2 (i) Calculate the mass of phosphate released by the production of 400 kg of shrimp. … kg [1] (ii) A salmon farmer claimed that salmon aquaculture is better for the environment compared with shrimp aquaculture. Use Table 4.1 to discuss the farmer’s claim. … … … … … … [3] (iii) Integrated multi-trophic aquaculture is a method of aquaculture where several species of organism are grown together. Integrated multi-trophic aquaculture may reduce the negative impacts of aquaculture on the environment. Use Table 4.1 to suggest why growing mussels and seaweed in a salmon aquaculture system would reduce negative environmental impacts. … … … … … … … … [4] [Total: 12]

12 marks

Mark scheme: 4(a) any 4 of: 1 smolt placed into cages (from stocks) ; 2 feed on (high) protein pellets / feed regularly / AW ; 3 keep fish of different ages / sizes in separate cages / AW ; 4 place in open water / estuary / coastal water ; 5 water currents remove waste / deliver food / nutrients / oxygen ; 6 monitoring of abiotic factors / named factor ; 7 add pesticides / antibiotics / vaccines / include cleaner fish / keep stocking density low / AW ; 8 prevent predators getting in / AW ; 9 harvest / reach maturity after one / two years ; 4(b)(i) 32 (kg) ; 1 4(b)(ii) any 3 of: 1 (salmon aquaculture) releases less phosphate / releases less carbon dioxide / causes less land loss / ORA ; 2 (less phosphate) so less eutrophication / fewer algal blooms / ORA ; 3 less oxygen loss / AW / ORA ; 4 (less carbon dioxide), so less global warming / less (enhanced) greenhouse effect / less acidification / AW / ORA ; 5 less loss of, biodiversity / habitats, due to less land loss / ORA ; 6 shrimp aquaculture has less biotic depletion so fewer wild organisms are lost / less loss of biodiversity (in oceans) / ORA ; 3 4(b)(iii) any 4 of: 1 seaweed / mussels, remove phosphate (from salmon) / AW ; 2 less eutrophication / algal blooms / AW ; 3 seaweed removes carbon dioxide / reduces carbon dioxide ; 4 (carbon dioxide) produced by respiration / decay / decomposition ; 5 seaweed will, increase / release oxygen, (from photosynthesis) ; 6 from photosynthesis ; 7 (seaweed / mussels) has little (extra) biotic depletion / AW ; 8 (seaweed / mussels) has little extra land loss / land loss is insignificant / AW ; 9 seaweed can provide a habitat for other organisms / increase biodiversity ; 4

This question in 9693/41 May/June 2023

3 Salmon are grown commercially around coastal areas using extensive aquaculture systems called salmon farms. (a) Outline the process of salmon aquaculture in extensive systems. … … … … … … … … [4] (b) Scientists investigated the escape of salmon from salmon farms into the wild. Farmed salmon are fed food pellets that contain a dye. The dye accumulates in the body tissues of the salmon. Salmon were caught by rod-and-line from rivers and areas of sea close to a salmon farm. Salmon that had escaped from the salmon farm were identified by the presence of the dye in their body tissues. Fig. 3.1 shows the percentage of female salmon caught that had escaped from the salmon farm from 2000 to 2005. 90 80 70 60 percentage of 50female salmon caught that had escaped 40 30 20 10 0 2000 2001 2002 2003 2004 2005 year Fig. 3.1 (i) In 2005, a total of 53 female salmon were caught. Use Fig. 3.1 to calculate the number of female salmon caught that had escaped from the salmon farm. … [1] (ii) Suggest why the percentage of female salmon caught that had escaped increased from 2000 to 2005. … … … … [2] (c) In the wild, salmon lay eggs in the upstream areas of rivers. They lay the eggs in nests called redds. In 2005, the scientists investigated the presence of eggs produced by escaped salmon in rivers near the salmon farm. The scientists also took samples of the fertilised eggs and determined the percentage that hatched and developed into fish fry. They identified the eggs from female salmon that had escaped by the presence of the food dye. They also measured the range of concentration of dye in the eggs from each redd. The results are shown in Table 3.1. Table 3.1 redds number percentage of eggs range of dye of redds that developed into concentration in eggs fish fry redds with eggs containing dye 9 83 3.6% to 55% redds with eggs not containing dye 11 98 N/A (i) Suggest a reason for the range of dye concentration in the eggs laid by the escaped salmon. … … [1] (ii) Discuss the impacts of the escaped salmon on the wild salmon populations. Use the information in Fig. 3.1 and Table 3.1 to support your answer. … … … … … … … … [4] (iii) Suggest why the information in Table 3.1 may be insufficient to make a firm conclusion on the impact of escaped salmon on wild salmon populations. … … … … [2] [Total: 14]

14 marks

Mark scheme: 3(a) any 4 of: 4 1 brood salmon are used to produce eggs and sperm / AW ; 2 eggs / small fish / fry / alevins, kept in (indoor), hatcheries / tanks ; 3 transfer to, cages / nets, in sea / outdoors / AW ; 4 keep large and small fish apart / separate by age / AW ; 5 add feed / add feed pellets / AW ; 6 use of pesticides / antibiotics / vaccinations / AW ; 7 prevent predator action / AW ; 8 ocean currents supply oxygen / food / remove waste ; 3(b)(i) (82 / 100  53 =) 43 ; 1 3(b)(ii) any 2 of: 2 1 salmon live for more than one year / AW ; 2 more salmon escape each year / AW ; 3 damage to the cages / bad weather disrupting the cages / cages get larger holes over time / AW ; 4 number of wild salmon is decreasing / AW ; 5 increased number of salmon farms / more stock kept / AW ; 6 credit reason for decrease in number of wild salmon / AW ; 3(c)(i) any 1 of: 1 1 salmon that have lived for several years outside the farm will have less dye in body / will have been eating more wild food / AW ; 2 recently escaped salmon will have higher dye concentrations ; 3 egg sizes vary (so concentration varies) / wild salmon fertilised salmon so dye reduced ; 4 different amounts of dye were given to salmon when in the farm / some salmon ate more food when in the farm ; 3(c)(ii) any 4 of: 4 1 escaped salmon are able to breed / reproduce / AW ; 2 but egg viability / hatching rate is lower than wild salmon / do not develop as well as wild salmon / AW ; 3 escaped salmon breed for several years ; 4 shown by the wide range of dye in eggs ; 5 escaped salmon outcompeting wild salmon / consume more food / AW ; 6 wild salmon may lose breeding sites / habitats / AW ; 7 fewer wild salmon survive / proportion of wild salmon are decreasing / AW ; 8 salmon may pass on disease to the wild salmon ; 9 escaped salmon affect the gene pool / reduce genetic diversity / have weaker alleles / AW ; 3(c)(iii) any 2 of: 2 1 a very small sample size has been used / not enough data / AW ; 2 no mention of how many eggs, develop / produced (as it is a percentage) / redds may have different numbers of eggs / AW ; 3 the wild salmon may breed in different areas (compared with escaped) / no clear information about locations / no information about size of habitat / no information about distances escaped salmon travel / AW ; 4 the dye colour may be lost from eggs / salmon after several years very wide difference in dye concentration / dye is not passed on into adults from eggs / AW ; 5 no data about disease or genetics of salmon ; 6 no direct data to show how wild salmon populations have changed / correlation does not show causation / AW ;

This question in 9693/41 Oct/Nov 2023

3 Salmon are grown commercially around coastal areas using extensive aquaculture systems called salmon farms. (a) Outline the process of salmon aquaculture in extensive systems. … … … … … … … … [4] (b) Scientists investigated the escape of salmon from salmon farms into the wild. Farmed salmon are fed food pellets that contain a dye. The dye accumulates in the body tissues of the salmon. Salmon were caught by rod-and-line from rivers and areas of sea close to a salmon farm. Salmon that had escaped from the salmon farm were identified by the presence of the dye in their body tissues. Fig. 3.1 shows the percentage of female salmon caught that had escaped from the salmon farm from 2000 to 2005. 90 80 70 60 percentage of 50female salmon caught that had escaped 40 30 20 10 0 2000 2001 2002 2003 2004 2005 year Fig. 3.1 (i) In 2005, a total of 53 female salmon were caught. Use Fig. 3.1 to calculate the number of female salmon caught that had escaped from the salmon farm. … [1] (ii) Suggest why the percentage of female salmon caught that had escaped increased from 2000 to 2005. … … … … [2] (c) In the wild, salmon lay eggs in the upstream areas of rivers. They lay the eggs in nests called redds. In 2005, the scientists investigated the presence of eggs produced by escaped salmon in rivers near the salmon farm. The scientists also took samples of the fertilised eggs and determined the percentage that hatched and developed into fish fry. They identified the eggs from female salmon that had escaped by the presence of the food dye. They also measured the range of concentration of dye in the eggs from each redd. The results are shown in Table 3.1. Table 3.1 redds number percentage of eggs range of dye of redds that developed into concentration in eggs fish fry redds with eggs containing dye 9 83 3.6% to 55% redds with eggs not containing dye 11 98 N/A (i) Suggest a reason for the range of dye concentration in the eggs laid by the escaped salmon. … … [1] (ii) Discuss the impacts of the escaped salmon on the wild salmon populations. Use the information in Fig. 3.1 and Table 3.1 to support your answer. … … … … … … … … [4] (iii) Suggest why the information in Table 3.1 may be insufficient to make a firm conclusion on the impact of escaped salmon on wild salmon populations. … … … … [2] [Total: 14]

14 marks

Mark scheme: 3(a) any 4 of: 4 1 brood salmon are used to produce eggs and sperm / AW ; 2 eggs / small fish / fry / alevins, kept in (indoor), hatcheries / tanks ; 3 transfer to, cages / nets, in sea / outdoors / AW ; 4 keep large and small fish apart / separate by age / AW ; 5 add feed / add feed pellets / AW ; 6 use of pesticides / antibiotics / vaccinations / AW ; 7 prevent predator action / AW ; 8 ocean currents supply oxygen / food / remove waste ; 3(b)(i) (82 / 100  53 =) 43 ; 1 3(b)(ii) any 2 of: 2 1 salmon live for more than one year / AW ; 2 more salmon escape each year / AW ; 3 damage to the cages / bad weather disrupting the cages / cages get larger holes over time / AW ; 4 number of wild salmon is decreasing / AW ; 5 increased number of salmon farms / more stock kept / AW ; 6 credit reason for decrease in number of wild salmon / AW ; 3(c)(i) any 1 of: 1 1 salmon that have lived for several years outside the farm will have less dye in body / will have been eating more wild food / AW ; 2 recently escaped salmon will have higher dye concentrations ; 3 egg sizes vary (so concentration varies) / wild salmon fertilised salmon so dye reduced ; 4 different amounts of dye were given to salmon when in the farm / some salmon ate more food when in the farm ; 3(c)(ii) any 4 of: 4 1 escaped salmon are able to breed / reproduce / AW ; 2 but egg viability / hatching rate is lower than wild salmon / do not develop as well as wild salmon / AW ; 3 escaped salmon breed for several years ; 4 shown by the wide range of dye in eggs ; 5 escaped salmon outcompeting wild salmon / consume more food / AW ; 6 wild salmon may lose breeding sites / habitats / AW ; 7 fewer wild salmon survive / proportion of wild salmon are decreasing / AW ; 8 salmon may pass on disease to the wild salmon ; 9 escaped salmon affect the gene pool / reduce genetic diversity / have weaker alleles / AW ; 3(c)(iii) any 2 of: 2 1 a very small sample size has been used / not enough data / AW ; 2 no mention of how many eggs, develop / produced (as it is a percentage) / redds may have different numbers of eggs / AW ; 3 the wild salmon may breed in different areas (compared with escaped) / no clear information about locations / no information about size of habitat / no information about distances escaped salmon travel / AW ; 4 the dye colour may be lost from eggs / salmon after several years very wide difference in dye concentration / dye is not passed on into adults from eggs / AW ; 5 no data about disease or genetics of salmon ; 6 no direct data to show how wild salmon populations have changed / correlation does not show causation / AW ;

This question in 9693/42 Oct/Nov 2023

3 Salmon are grown commercially around coastal areas using extensive aquaculture systems called salmon farms. (a) Outline the process of salmon aquaculture in extensive systems. … … … … … … … … [4] (b) Scientists investigated the escape of salmon from salmon farms into the wild. Farmed salmon are fed food pellets that contain a dye. The dye accumulates in the body tissues of the salmon. Salmon were caught by rod-and-line from rivers and areas of sea close to a salmon farm. Salmon that had escaped from the salmon farm were identified by the presence of the dye in their body tissues. Fig. 3.1 shows the percentage of female salmon caught that had escaped from the salmon farm from 2000 to 2005. 90 80 70 60 percentage of 50female salmon caught that had escaped 40 30 20 10 0 2000 2001 2002 2003 2004 2005 year Fig. 3.1 (i) In 2005, a total of 53 female salmon were caught. Use Fig. 3.1 to calculate the number of female salmon caught that had escaped from the salmon farm. … [1] (ii) Suggest why the percentage of female salmon caught that had escaped increased from 2000 to 2005. … … … … [2] (c) In the wild, salmon lay eggs in the upstream areas of rivers. They lay the eggs in nests called redds. In 2005, the scientists investigated the presence of eggs produced by escaped salmon in rivers near the salmon farm. The scientists also took samples of the fertilised eggs and determined the percentage that hatched and developed into fish fry. They identified the eggs from female salmon that had escaped by the presence of the food dye. They also measured the range of concentration of dye in the eggs from each redd. The results are shown in Table 3.1. Table 3.1 redds number percentage of eggs range of dye of redds that developed into concentration in eggs fish fry redds with eggs containing dye 9 83 3.6% to 55% redds with eggs not containing dye 11 98 N/A (i) Suggest a reason for the range of dye concentration in the eggs laid by the escaped salmon. … … [1] (ii) Discuss the impacts of the escaped salmon on the wild salmon populations. Use the information in Fig. 3.1 and Table 3.1 to support your answer. … … … … … … … … [4] (iii) Suggest why the information in Table 3.1 may be insufficient to make a firm conclusion on the impact of escaped salmon on wild salmon populations. … … … … [2] [Total: 14]

14 marks

Mark scheme: 3(a) any 4 of: 4 1 brood salmon are used to produce eggs and sperm / AW ; 2 eggs / small fish / fry / alevins, kept in (indoor), hatcheries / tanks ; 3 transfer to, cages / nets, in sea / outdoors / AW ; 4 keep large and small fish apart / separate by age / AW ; 5 add feed / add feed pellets / AW ; 6 use of pesticides / antibiotics / vaccinations / AW ; 7 prevent predator action / AW ; 8 ocean currents supply oxygen / food / remove waste ; 3(b)(i) (82 / 100  53 =) 43 ; 1 3(b)(ii) any 2 of: 2 1 salmon live for more than one year / AW ; 2 more salmon escape each year / AW ; 3 damage to the cages / bad weather disrupting the cages / cages get larger holes over time / AW ; 4 number of wild salmon is decreasing / AW ; 5 increased number of salmon farms / more stock kept / AW ; 6 credit reason for decrease in number of wild salmon / AW ; 3(c)(i) any 1 of: 1 1 salmon that have lived for several years outside the farm will have less dye in body / will have been eating more wild food / AW ; 2 recently escaped salmon will have higher dye concentrations ; 3 egg sizes vary (so concentration varies) / wild salmon fertilised salmon so dye reduced ; 4 different amounts of dye were given to salmon when in the farm / some salmon ate more food when in the farm ; 3(c)(ii) any 4 of: 4 1 escaped salmon are able to breed / reproduce / AW ; 2 but egg viability / hatching rate is lower than wild salmon / do not develop as well as wild salmon / AW ; 3 escaped salmon breed for several years ; 4 shown by the wide range of dye in eggs ; 5 escaped salmon outcompeting wild salmon / consume more food / AW ; 6 wild salmon may lose breeding sites / habitats / AW ; 7 fewer wild salmon survive / proportion of wild salmon are decreasing / AW ; 8 salmon may pass on disease to the wild salmon ; 9 escaped salmon affect the gene pool / reduce genetic diversity / have weaker alleles / AW ; 3(c)(iii) any 2 of: 2 1 a very small sample size has been used / not enough data / AW ; 2 no mention of how many eggs, develop / produced (as it is a percentage) / redds may have different numbers of eggs / AW ; 3 the wild salmon may breed in different areas (compared with escaped) / no clear information about locations / no information about size of habitat / no information about distances escaped salmon travel / AW ; 4 the dye colour may be lost from eggs / salmon after several years very wide difference in dye concentration / dye is not passed on into adults from eggs / AW ; 5 no data about disease or genetics of salmon ; 6 no direct data to show how wild salmon populations have changed / correlation does not show causation / AW ;

This question in 9693/43 Oct/Nov 2023

3 Aquaculture in coastal areas is used to produce large quantities of shrimp. Shrimp aquaculture can cause environmental pollution. Scientists are researching ways to make shrimp aquaculture more environmentally sustainable. (a) (i) Outline the process for aquaculture of shrimp. … … … … … … [3] (ii) Give two strategies that can be used to help ensure the long-term success of aquaculture. 1 … … 2 … … [2] (b) Mussels are filter-feeding organisms that consume microalgae and other organic waste. Wastewater from shrimp aquaculture sites contains large amounts of ammonium ions that pollute the sea. The ammonium ions are converted to nitrate ions by bacteria. Scientists investigated the effects of growing mussels and adding microalgae on the removal of nitrate ions from wastewater produced by shrimp aquaculture. • Wastewater from a shrimp aquaculture site was collected and placed into tanks. • Different densities of mussels were added to the tanks. • The same mass of microalgae was added to each tank. • The nitrate ion concentration of the water was measured at the start and every day for the next six days. The results are shown in Fig. 3.1. 3.0 8 mussels 2.5 per square metre 2.0 nitrate ion concentration 1.5 no mussels / mg dm–3 1.0 4 mussels per square 0.5 metre 0 0 1 2 3 4 5 6 time / days Fig. 3.1 (i) Calculate the mean rate of change of nitrate ion concentration with no mussels over the six-day period. State the unit. Show your working. … [3] (ii) Describe the effects of adding different densities of mussels on the removal of nitrate ions from the water over the six-day period. … … … … … … [3] (c) The scientists also measured dissolved oxygen concentration in the water every day for the six days. The results are shown in Fig. 3.2. 12 10 8 dissolved oxygen 6 no musselsconcentration / mg dm–3 4 mussels 4 per square metre 8 mussels 2 per square metre 0 0 1 2 3 4 5 6 time / days Fig. 3.2 (i) The same mass of microalgae was added to each tank at the start. Explain the change in dissolved oxygen concentration in the water up to day three when microalgae were present with no mussels. … … … … [2] (ii) Ammonium ions are converted into nitrate ions by bacteria in the water. Nitrate ions are absorbed by algae. Mussels consume algae. Discuss the effects of adding different densities of mussels on the changes in concentration of oxygen and nitrate ions in the water. Use the information in Fig. 3.1 and Fig. 3.2 to support your answer. … … … … … … … … [4] [Total: 17]

17 marks

Mark scheme: 3(a)(i) any 3 of: 1 eggs placed / larvae grown in indoor tanks / AW ; 2 sterile conditions / AW ; 3 (postlarvae) transferred to nurseries / nursery tanks ; 4 (post)larvae / juveniles, transferred into raceway ponds / outdoor pools / natural water / growout pools / AW ; 5 feed / algae provided / AW ; 6 AVP ; 3(a)(ii) any 2 of: 1 availability of stock / AW ; 2 availability of clean water / water purification / remove wastes / AW ; 3 availability of feed / AW ; 4 efficiency of use of feed / use high quality feed / AW ; 5 availability of labour / AW ; 6 disease management / AW ; 7 availability of location / space / AW ; 8 (market) demand / AW ; 9 access to markets / transport / AW ; 10 return on investment / profit making / money to reinvest / AW ; 2 3(b)(i) 0.083 ;; (two marks) 2(.00) – 1.5(0) or 1.5 – 2 or 0.5 or ÷ 6 (for one mark only) mg dm-3 day-1 ; 3 3(b)(ii) any 3 of: 1 with no mussels, there is a (steady) decrease ; 2 with four mussels there is a greater / steeper / AW, decrease ; 3 with eight mussels there is decrease up to 2 days and then an increase ; 4 correctly manipulated data ; 3 Question Answer Marks 3(c)(i) any 2 of: 1 algae photosynthesise ; 2 photosynthesis / algae, produce / release oxygen ; 3 algae increase in population (as they absorb nitrate ions) ; 4 no / less, respiration (from mussels) (to remove oxygen) ; 2 3(c)(ii) any 4 of: 1 oxygen decreases more with 8 mussels / AW ; 2 nitrate increases with 8 mussels / AW ; 3 more / many algae consumed / AW, with 8 mussels ; 4 less nitrate removed / absorbed by algae (with 8 mussels) ; 5 faeces / waste, decomposes / decays / AW ; 6 respiration (by mussels / bacteria) removes oxygen ; 7 less photosynthesis to release oxygen with 8 mussels ; 4

This question in 9693/41 May/June 2024