Fishing — AQA A-Level Environmental Science

The fishing topic investigates how marine and freshwater ecosystems are exploited to supply global animal protein, alongside the resulting ecological degradation. It covers wild capture techniques including demersal trawling, pelagic longlining, and purse seining, detailing their distinct impacts on benthic habitats, trophic webs, and bycatch mortality.

Students evaluate resource management tools including Catch Per Unit Effort (CPUE), Total Allowable Catches (TACs), fishing effort restrictions, and Marine Protected Areas (MPAs). This topic links core biological principles of population growth and carrying capacity directly to geopolitical, environmental, and socio-economic conservation challenges.

• →Demersal vs Pelagic Fishing: Understanding the operational differences and distinct ecological impacts of seafloor gear (dredges, beam trawls) versus open-water gear (drift nets, longlines, purse seines).
• →Maximum Sustainable Yield (MSY): The maximum harvest rate equivalent to the population growth rate at K/2, and the inherent ecological risks of targeting MSY in variable marine environments.
• →Bycatch and Ghost Fishing: Unintended capture of non-target organisms (juveniles, cetaceans, seabirds, turtles) and the ongoing mortality inflicted by lost, abandoned synthetic fishing gear.
• →Management and Regulation: Enforcing Total Allowable Catches (TACs), individual transferable quotas (ITQs), mesh size restrictions, square mesh panels, acoustic deterrents, and temporal/spatial marine reserves.
• →Catch Per Unit Effort (CPUE): An index of fish population density; a declining CPUE signifies declining stock abundance even if total landings temporarily remain stable due to technological creep.

• Defines pelagic trawling as towing a net through the midwater column above the seabed to catch shoaling fish.
• Explains that the gear targets pelagic species such as herring or mackerel and can be highly effective on dense shoals.
• Identifies limited seabed contact as an advantage relative to demersal trawling.
• Describes poor selectivity, including retention of juveniles, bycatch and possible entanglement of marine mammals.
• Notes the high fuel and energy input associated with towing large nets.
• Suggests management measures such as mesh-size rules, escape panels or acoustic deterrents to reduce bycatch.

• 💡State clearly where in the water column the net operates before discussing impacts.
• 💡Link each advantage or disadvantage to one of the four criteria: effectiveness, selectivity, energy inputs and environmental impacts.
• 💡Use a named target species to make the description concrete.
• 💡When explaining MSY, always sketch or refer to a logistic growth curve and explicitly state that the highest population growth rate occurs at intermediate population density (K/2).
• 💡Distinguish between biological overfishing (harvesting above MSY leading to reduced recruitment) and economic overfishing (excessive effort yielding diminishing financial returns).
• 💡In evaluate questions, present both direct conservation benefits and enforcement challenges (such as flag-of-convenience vessels, discarding, and illegal, unreported, and unregulated [IUU] fishing).

• Confuses pelagic trawling with demersal trawling; state that pelagic gear works in midwater above the seabed while demersal gear works near the bottom.
• Claims pelagic trawling causes no environmental impact; acknowledge bycatch, entanglement and fuel use even where seabed contact is limited.
• Assumes large mesh alone solves selectivity; combine mesh rules with escape panels and other measures for a fuller answer.
• Stable annual landing figures indicate a healthy fish stock: Total landing volume can remain constant despite crashing populations if fishing effort, vessel power, and search technologies (sonar, GPS) increase; CPUE is the accurate ecological indicator.
• Fish populations always recover rapidly if fishing stops: Extreme overexploitation can cause depensation (Allee effect), habitat structural degradation, or trophic cascades where competitors and predators suppress larval survival, preventing recovery.
• Bycatch only refers to marine mammals and turtles: Bycatch includes non-marketable commercial fish, undersized juveniles of target species, benthic invertebrates, seabirds, and non-target teleosts.

1. 1Day 1-2: Master fishing techniques by diagramming demersal trawling, pelagic longlining, drift netting, and purse seining, annotating each with target species and specific bycatch risks.
2. 2Day 3-4: Learn population dynamics models, focusing on MSY, logistic curves, the meaning of CPUE, and mathematical exercises calculating percentage stock changes.
3. 3Day 5-6: Compare fisheries management methods: technical measures (mesh size, TEDs, pingers), input controls (vessel size, days at sea), and output controls (TACs, quotas).
4. 4Day 7: Practise AQA 6-mark and 9-mark evaluation questions covering marine protected areas and the European Common Fisheries Policy (CFP).

• 📋Data Analysis / Calculation: Interpreting landing statistics versus fishing effort to deduce changes in CPUE, or calculating MSY values from logistic growth models.
• 📋Method Evaluation: 6-mark questions assessing the strengths and limitations of fishing gear modifications (e.g. circle hooks, streamer lines, turtle excluder devices).
• 📋Extended Policy Essay: 9-mark evaluations of legislative tools such as Total Allowable Catches (TACs), discard bans, and Marine Protected Areas (MPAs) in conserving marine biodiversity.