Environmental Management (0680) | Management of the harvesting of marine species

🌊 Environmental Management Study Notes: Management of Marine Harvesting (Syllabus 5.4) 🐟

Hello future environmental managers! This chapter is all about ensuring that we can still enjoy fish and other seafood far into the future. It’s a crucial topic because the health of the oceans directly impacts human survival. If we take too many fish, the whole marine ecosystem collapses, and our food source disappears!

We will explore the smart strategies needed to harvest marine species sustainably—meaning we take what we need today without preventing future generations from meeting their needs.

1. The Problem: Why Management is Essential

Before we manage, we need to understand the threat. The main impact of uncontrolled harvesting is overfishing—catching fish faster than the population can naturally replace itself.

Key Negative Impacts of Poor Harvesting:

• Stock Depletion: Fish populations (stocks) fall to dangerously low levels.
• Bycatch: Non-target species (like dolphins, sea turtles, or unwanted fish) are accidentally caught and often die, leading to massive waste and biodiversity loss.
• Habitat Destruction: Certain fishing gear, like bottom trawlers, physically destroys marine habitats such as coral reefs and seagrass beds.

Quick Takeaway: Management strategies must protect fish numbers, minimize bycatch, and keep habitats safe.

2. Technical Management Strategies: Controlling the Gear

One of the most effective ways to manage fishing is by controlling the equipment used. This targets *how* and *what* is caught.

A. Regulating Net Types and Mesh Size

This strategy focuses on making sure that only mature fish, which have had a chance to reproduce, are harvested.

• Mesh Size: The size of the holes in the fishing nets.
• The Rule: Legislation dictates the minimum mesh size allowed.
• Evaluation:

  • Benefit: Larger mesh sizes allow juvenile fish (young fish) to escape, grow, and reproduce. This keeps the population sustainable.

  • Drawback: Larger mesh might still catch smaller, non-target species if they are oddly shaped, contributing to bycatch.

Think of it this way: If you use a sieve with small holes to drain pasta, you catch everything. If you use a sieve with large holes, the tiny pasta pieces (juvenile fish) fall back into the water, while the big potatoes (adult fish) are kept.

B. Species-Specific Methods (Selectivity)

These methods aim to catch only the intended species, dramatically reducing wasteful bycatch.

• Pole and Line Fishing:

  • This is a selective method where individual fish (often tuna) are caught one by one using a hook attached to a pole.

  • Evaluation: Extremely low bycatch rate and very little habitat damage. It's often promoted as a sustainable method.

• Other Selective Methods: Modifying trawling gear (e.g., adding escape panels for turtles) or using specific bait to only attract the target species.

Key Takeaway: Controlling gear (mesh size) and methods (pole and line) ensures we target adults and minimize accidental killing (bycatch).

3. Regulatory Management Strategies: Limits and Boundaries

These strategies involve setting legal limits on *when*, *where*, and *how much* fishing can occur.

A. Quotas (Total Allowable Catch, TAC)

A quota is a set legal limit on the number or weight of a particular fish species that can be caught over a specific time period (usually annually).

• Mechanism: Scientists determine the maximum sustainable yield (MSY)—the highest rate at which a species can be harvested without reducing the stock size—and the government sets the quota below this level.
• Benefit: Directly limits the total exploitation, allowing stocks to recover.
• Drawback:

  • Difficult to monitor, especially on the high seas.

  • Can lead to the "Race to Fish," where boats rush to catch their share before the quota is reached, causing market instability and safety concerns.

  • Often leads to 'discarding' (throwing dead, unwanted fish overboard) if a boat has already filled its quota for that specific species.

B. Closed Seasons (Time Limits)

Fishing is prohibited for certain species during their critical life stages.

• Mechanism: Banning fishing during the breeding season.
• Benefit: Allows adult fish to reproduce successfully, ensuring a new generation (recruitment) replenishes the stock.

C. Protected Areas and Reserves (Spatial Limits)

Specific areas of the ocean are declared off-limits to fishing, similar to a national park on land. These are called Marine Protected Areas (MPAs).

• Benefit:

  • They act as safe "nurseries" where fish can breed and grow undisturbed.

  • The population within the reserve often grows so large that adult fish eventually "spill over" and swim into surrounding fished areas, increasing catches outside the reserve (the "spillover effect").

• Drawback: Requires significant surveillance and enforcement to prevent illegal fishing.

Did you know? Even if a small percentage of the ocean is protected by MPAs, the increase in fish biomass and density can be huge!

4. Legal and International Management Strategies

Because oceans don't respect borders, managing marine species requires laws, monitoring, and global cooperation.

A. National Conservation Laws

These are laws implemented by individual countries within their territorial waters (usually 200 nautical miles from shore, known as the Exclusive Economic Zone, EEZ).

• Minimum Landing Size (MLS): Fish below a certain length must be immediately returned to the sea, alive. This supports the mesh size regulations by providing a second layer of protection for juveniles.
• Licensing: Requiring all commercial fishing vessels to have a permit, allowing governments to track and limit the number of active vessels.

Common Mistake Alert: Mesh size prevents small fish from being caught, while MLS forces fishermen to throw back small fish that *were* caught, ensuring they don't enter the market.

B. International Agreements and Monitoring

For fish that migrate long distances (like tuna or swordfish) or stocks in international waters (the high seas), international collaboration is vital.

• Regional Fisheries Management Organizations (RFMOs): These are groups of countries that share an interest in a specific region or species. They meet to agree on quotas, fishing seasons, and gear restrictions for the high seas.
• Role of Monitoring: Agreements need robust monitoring and implementation. This often involves:

  • Vessel Monitoring Systems (VMS): GPS tracking systems on boats that allow authorities to check if vessels are fishing illegally in protected areas or during closed seasons.

  • Inspections: Checking catches when boats land in port to ensure compliance with quotas and MLS rules.

• Evaluation: International agreements are difficult because countries must willingly cooperate. Illegal, Unreported, and Unregulated (IUU) fishing remains a massive problem globally, undermining conservation efforts.

5. Evaluation Summary: Weighing the Strategies

When evaluating management strategies (a common exam skill), consider the effectiveness and practical challenges of implementation.

Strategy	Benefit (Effectiveness)	Challenge (Practicality)
Larger Mesh Size	Allows juveniles to escape and grow.	May not reduce bycatch of all unwanted species; difficult to enforce at sea.
Quotas (TAC)	Directly limits total harvest amount.	Hard to monitor compliance; can encourage discarding (waste).
Closed Seasons	Protects fish during critical spawning/breeding periods.	Causes temporary economic hardship for fishers; requires good biological timing.
MPAs (Reserves)	Creates undisturbed nursery areas; boosts populations via 'spillover'.	Requires political will; conflicts with fishers; expensive enforcement.

Final Key Takeaway: Effective management requires a combination of technical controls (gear), spatial/temporal limits (MPAs, seasons), and robust legal frameworks (quotas, international agreements).

Don't worry if all the abbreviations seem overwhelming! Just remember that management is about setting rules on WHAT (mesh size), HOW MUCH (quotas), and WHERE/WHEN (MPAs and closed seasons) we take from the sea.