Extended response Extended marine investigation

Transcription

1 Marine Science 2013 Sample assessment instrument and indicative response Extended response Extended investigation This sample is intended to inform the design of assessment instruments in the senior phase of learning. It highlights the qualities of student work and the match to the syllabus standards. Dimensions assessed Knowledge and understanding Investigation and analysis Evaluation and communication Assessment instrument The response presented in this sample is in response to an assessment item. Extended research response Extended investigation Inquiry-based investigation: environment Context: aquaculture Research question: To what extent does variation in diet influence the growth rate of redclaw, Cherax quadricarinatus? Supporting documentation: scientific journal Conditions Year 11 written response words students may use class time and their own time to conduct research and develop a response

2 Task Determine the impact of variations in dietary makeup upon the development of redclaw. You are required to assess the differences in development of redclaw fed on diets with varying nutritional elements over a 5-week period. Your findings are to be presented to a local aquaculture company keen to increase their return on investment. Your presentation should include justified conclusions and recommendations. You must present your response as a scientific report. Tabulated data, diagrams and charts should be used as appropriate. Carrying out the investigation In conducting the investigation, you must: follow an inquiry-based investigation process formulate a hypothesis and plan your investigation complete risk assessments to analyse and mitigate potential hazards and ensure animal welfare and ethics requirements are met collect, select and organise information from primary and/or secondary sources, including the construction of graphical representations analyse and interpret information, identifying and explaining relationships, trends and patterns evaluate information to draw conclusions and make decisions and recommendations, including modifications to equipment and procedures. Writing the report The scientific report must include at least the following sections: Introduction Results Analysis of data Evaluation Conclusion. Queensland Studies Authority January

3 Instrument-specific criteria and standards Student responses have been matched to instrument-specific criteria and standards; those which best describe the student work in this sample are shown below. For more information about the syllabus dimensions and standards descriptors, see assessment.html. Standard A Knowledge and understanding The student work has the following characteristics: thorough definition and description of aquaculture concepts thorough explanation of systems using a comprehensive range of concepts and models discerning and systematic application of understandings to aquaculture issues and problems. Investigation and analysis The student work has the following characteristics: formulation of purposeful and relevant hypotheses and thorough plans for investigations purposeful and collection of reliable primary data using research skills purposeful and selection and organisation of information from reliable and valid primary and secondary sources thorough analysis and interpretation of information to identify and explain relationships, trends and patterns. Evaluation and communication The student work has the following characteristics: thorough evaluation of information to draw logical conclusions and make purposeful and relevant decisions and recommendations reasoned and valid justification of conclusions, decisions and recommendations about aquaculture issues and problems coherent and clear communication using well-chosen language conventions to suit audiences and purposes. Note: Colour highlights have been used in the table to emphasise the qualities that discriminate between the standards. Key Qualifier Cognitive process Element Queensland Studies Authority January

4 Student response Standard A The annotations show the match to the instrument-specific standards. Comments Thorough definition and description of aquaculture concepts Discerning and systematic application of understandings to aquaculture issues and problems selection and organisation of information from reliable and valid secondary sources Introduction Redclaw crayfish (Cherax quadricarinatus) have a number of characteristics that make them suitable for aquaculture (i.e. farming of aquatic organisms). They have simple life-cycles and can tolerate variations in water quality and climate. Redclaw require a low protein diet and grow to commercial size in about nine months (Food and Agriculture Organization of the United Nations 2014). Crayfish are mainly detritivores they feed on decaying plants and animal materials and the organisms associated with this decomposition (NSW Department of Primary Industries n.d.). In an aquaculture setting, this means that they can survive on a wide variety of food sources. While commercial crayfish pellets are recommended, many producers use pellets designed for other uses. For optimum redclaw growth, their diet should have a protein content of around 20% (Aquaculture Council of Western Australia n.d.). Fish meal pellets can be bought in bulk for around $10/kg. Dry food pellets for other pets is much cheaper around $1 2/kg. The aim of this investigation is to determine whether redclaw fed fish meal pellets will grow more quickly than those fed dry dog food. This will help to establish whether or not the additional cost of fish meal pellets can be justified for a commercial aquaculture operation. Table 1: Nutritional composition of different redclaw diets* Component Fish meal Dog food Protein 45% 28% Coherent and clear communication using wellchosen language conventions to suit audiences and purposes Formulation of purposeful and relevant hypotheses and thorough plans for investigations Fat 20% 16% Carbohydrates 16% 48% Fibre 2% 6% * Taken from packaging information Table 1 shows that dog food has a protein content of 28% which is close to the optimum value of 20%. Fish meal pellets contain 45% protein. Since this is greater than the amount required for optimum growth, it is expected that redclaw fed the fish meal pellets will grow more slowly than those fed dry dog food. Notes on Method 6 redclaw were placed in each tank. Each redclaw was identified with a different coloured piece of tape. Redclaw were fed the recommended amount of fish meal pellets or an equivalent mass of dog food. Each week, the length and mass of each redclaw was measured and the water quality was monitored. Half (i.e. 15 L) of the water in each tank was changed each week Constant water temperature (23 C) and ph (7.2) were maintained in both tanks. Plans for the investigation have been more fully documented in the scientific journal which has not been included here. Queensland Studies Authority January

5 Comments Results Table 2: Redclaw length data Redclaw length (cm) Week purple red pink green peach blue Average collection of reliable primary data using research skills * Change (%) *Anomaly Redclaw length (cm) Week purple red pink green peach blue Average Change (%) Figure 1: Change in average redclaw length selection and organisation of information from reliable and valid primary sources Length (cm) Week Queensland Studies Authority January

6 Comments Table 3: Redclaw mass data Redclaw mass (g) Week purple red pink green peach blue Average collection of reliable primary data using research skills * Change (%) *Anomaly Redclaw mass (g) Week purple red pink green peach blue Average Change (%) Figure 2: Change in average redclaw mass selection and organisation of information from reliable and valid primary sources Mass (g) Week Queensland Studies Authority January

7 Comments collection of reliable primary data using research skills selection and organisation of information from reliable and valid primary sources Thorough analysis and interpretation of information to identify and explain relationships, trends and patterns Thorough explanation of systems using a comprehensive range of concepts and models Table 4: Water quality data for redclaw tanks Week Ammonia (ppm) Dissolved oxygen (ppm) Ammonia (ppm) Dissolved oxygen (ppm) * Average *Anomaly Analysis of data In this experiment, the redclaw that were fed fish meal pellets grew at a faster rate than redclaw fed dog food. This can be seen in Table 2, where the length of the redclaw in the fish meal tank increased by an average of 11% whereas the redclaw in the dog food tank apparently decreased in length by almost 2%. Since redclaw are crustaceans with hard exoskeletons, it is unlikely that they would shrink in this experiment. It is more likely that the change in length for the dog food redclaw was due to measurement error. Table 3 shows that the mass of the fish meal redclaw increased by an average of 9.1%, whereas the dog food redclaw mass increase was only 3.4%. It is possible that the fish meal redclaw grew at a faster rate because of the higher protein value of their diet. In the wild, redclaw live off a crude protein amount of 20 30% (Food and Agriculture Organization of the United Nations 2014) and the fish pellets contain even more protein than this. Although the protein content of the dog food was close to the recommended value of 20%, they did not seem to grow well on this. This may have been due to the poor water quality in this tank. Table 4 shows that the dog food tank consistently had an ammonia concentration of 10 ppm (except for the anomaly in Week 2) whereas the fish meal tank s average ammonia level was only around 5 ppm. High ammonia levels can be caused by waste products produced by redclaw and decomposition of uneaten food left behind in the bottom of the tank (NSW Department of Primary Industries n.d.). It was observed that all the pellets in the fish meal tank were eaten every time the redclaw were fed, whereas the dog food tank contained uneaten pellets. It is likely that this produced bacterial growth which increased the ammonia level. The lower dissolved oxygen concentration in the dog food tank supports the idea that bacteria may have been growing in it. The toxicity of ammonia depends on the temperature and ph of the water. At 23 C and ph of 7.2, the concentration of the toxic un-ionised form of ammonia would have been only 0.05 ppm (NSW Department of Primary Industries n.d.). Redclaw are tolerant of quite poor water quality and can stand un-ionised ammonia concentrations of up to 1.0 ppm (Rouse 1997). They can also tolerate dissolved oxygen concentrations down to 1.0 ppm (Rouse 1997). This means that, although the water quality in the dog food tank was worse than the fish meal tank, this does not seem to explain why the redclaw in the fish meal tank grew more quickly. Queensland Studies Authority January

8 Comments Thorough evaluation of information to draw logical conclusions and make purposeful and relevant decisions and recommendations Reasoned and valid justification of conclusions, decisions and recommendatio ns about aquaculture issues and problems Coherent and clear communication using wellchosen language conventions to suit audiences and purposes Evaluation Throughout the experiment, the data showed a high level of consistency. A few anomalies were identified, particularly in the length measurements in the dog food tank. For example, in Week 4, the purple redclaw s length dropped down unexpectedly and then returned to close to its original value the following week. Also, as discussed earlier, the decrease in the lengths of many these redclaw was unexpected and hard to explain. These issues were most likely due to human measurement errors. One way to improve the experiment in the future would be to clean the tanks more often to prevent the build-up of uneaten dog food and redclaw waste products which caused such high ammonia and low dissolved oxygen levels in the dog food tank. This would make it clear that the slow growth of redclaw in this tank was not due to poor water quality. Conclusion In this experiment, a diet of fish meal pellets caused redclaw to grow more quickly than feeding them dry dog food. For a commercial aquaculture business, this means that the extra cost of fish meal pellets may be justified. However, further investigation is needed to determine if the lower growth rate of the dog food red claw was due to poor water quality. Bibliography Aquaculture Council of Western Australia. Red Claw Husbandry and Disease Control. n.d. (accessed February 18, 2014). Food and Agriculture Organization of the United Nations. Cherax quadricarinatus en (accessed January 13, 2014). NSW Department of Primary Industries. Freshwater crayfish aquaculutre prospects. n.d. publications/species-freshwater/freshwater-crayfish---aquacultureprospects (accessed January 13, 2014).. Monitoring ammonia. n.d. publications/water-quality-management/monitoring-ammonia (accessed January 31, 2014). Rouse, Michael P. Masser and David B. Australian Red Claw Crayfish. April (accessed February 19, 2014). Acknowledgments The QSA acknowledges the contribution of Innisfail State High School in the preparation of this document. Queensland Studies Authority January