Comprehensive Study Guide for Fisheries and Fish Biology

Assessment Characteristics and Logistics

• Weighting: The assessment is weighted at $30\,\%$ of the total course grade.

• Format: The test will consist of a combination of diagrams, short-answer questions, and source analysis tasks.

• Date: The assessment is scheduled for Thursday of Week 10.

Fisheries Management by DPIRD

• Department Authority: Fisheries in Western Australia are managed by the Department of Primary Industries and Regional Development (DPIRD).

• The Four Broad Biological Regions (Bioregions): In Western Australia, recreational fisheries are managed across four distinct Bioregions based on geographical and ecological characteristics:

  • North Coast: Extending from the Northern Territory border to the Ashburton River.

  • Gascoyne Coast: Extending from the Ashburton River to the Zuytdorp Cliffs.

  • West Coast: Extending from the Zuytdorp Cliffs to Black Point.

  • South Coast: Extending from Black Point to the South Australian border.

• The Five Ecological Suites: Within each of the four Bioregions, species are managed according to five ecological suites based on their primary habitat and depth:

  • Estuarine: Fish that reside in or rely on estuaries.

  • Nearshore: Waters from the beach to a depth of approximately $20\,\text{m}$.

  • Offshore Demersal: Bottom-dwelling species inhabiting depths between $20\,\text{m}$ and $250\,\text{m}$.

  • Pelagic: Species residing in the upper layers of the open ocean.

  • Deepwater: Species found at depths greater than $250\,\text{m}$.

Management Tools and Ecological Purposes

DPIRD utilizes several regulatory tools to manage fish stocks effectively. Each tool serves a specific ecological goal:

• Size Limits:

  • Definition: Mandatory minimum (and sometimes maximum) lengths for kept fish.

  • Ecological Purpose: To ensure that fish have the opportunity to reach sexual maturity and spawn at least once before they are harvested, thereby replenishing the population.

• Bag Limits:

  • Definition: The maximum number of fish of a particular species or group that an individual fisher can take in a single day.

  • Ecological Purpose: To share the resource among a large number of fishers and to prevent overfishing of localized populations.

• Seasonal Closures:

  • Definition: Specific periods during the year when fishing for a particular species is prohibited.

  • Ecological Purpose: To protect species during vulnerable stages of their life cycle, most notably during spawning seasons when they congregate and are easily caught.

• Area Closures:

  • Definition: Specific geographic zones (such as Marine Parks or Fish Habitat Protection Areas) where fishing is restricted or banned.

  • Ecological Purpose: To protect critical habitats, provide refuges for biodiversity, and protect nursery grounds for juvenile fish.

• Gear Restrictions:

  • Definition: Limits on the type, size, and quantity of fishing equipment used (e.g., mesh size of nets, number of hooks per line).

  • Ecological Purpose: To reduce the efficiency of harvest to sustainable levels, minimize bycatch of non-target species, and prevent damage to the benthic environment.

• Licensing:

  • Definition: The requirement for fishers to obtain a legal permit for specific activities (e.g., fishing from a motorized boat, catching rock lobster).

  • Ecological Purpose: To monitor the total number of participants in the fishery, gather data for research, and generate revenue to fund conservation and management efforts.

Sustainability and "Fish for the Future"

• Fish for the Future Philosophy: This is the core management goal of DPIRD, emphasizing that current fishing activities must not compromise the ability of future generations to enjoy the same resources.

• Necessity of Sustainable Recreational Fishing: Recreational fishing must be sustainable because fish are a finite resource. Factors such as increasing population, improved fishing technology (like GPS and high-quality sonar), and environmental pressures mean that without management, stocks would quickly collapse, leading to a loss of biodiversity and recreational opportunity.

Fishing Knots and Applications

• Uni Knot: A versatile multipurpose knot used for connecting a hook, lure, or swivel to a fishing line. It is highly reliable and maintains much of the line's original breaking strength.

• Loop Knot: Used primarily to attach a lure to the line in a way that allows the lure to move freely and naturally in the water, rather than being restricted by a tight knot.

• Double Uni Knot: Generally used for joining two lines of similar or different diameters together, such as attaching a fluorocarbon leader to a braided main line.

Perth Metro Fishing Identification and Care

• Target Species in Perth Metro:

  • Australian Herring: Often found near limestone reefs and jetties. Best caught using light tackle and small lures or baits like maggots or prawns.

  • Whiting: Frequently found in sandy patches or the surf zone. Best caught using small hooks ($No. 4$ to $No. 6$) and baits like beach worms or squid strips.

• Catch and Release Care Tips: To ensure a high survival rate after release, follow these three steps:

  1. Use Barbless Hooks: Minimizes tissue damage and allows for a faster, easier removal of the hook.

  2. Minimize Air Exposure: Keep the fish in the water as much as possible. If it must be handled, ensure hands are wet to protect the fish's protective slime coating.

  3. Support the Body: Never hold a fish solely by the jaw or gills; support the belly to prevent internal organ damage.

Anatomy of a Bony Fish (Herring)

Anatomy must be studied specifically in the context of the Australian Herring. Key structures include:

• External Features:

  • Operculum: The hard, bony flap that covers and protects the gills while facilitating the pumping of water over them.

  • Lateral Line: A sensory organ consisting of a series of pores along the side of the fish used to detect vibrations and pressure changes in the water.

  • Caudal Fin: The tail fin, used primarily for propulsion and forward thrust.

  • Pectoral Fins: Located on either side behind the operculum, used for steering and balancing.

  • Dorsal Fin: Located on the back, providing stability and preventing the fish from rolling.

  • Anal Fin: Located on the ventral (bottom) side near the tail, contributing to stability during swimming.

• Internal Features:

  • Swim Bladder: A gas-filled sac that allows the fish to maintain buoyancy and change depths without wasting energy.

  • Gills: Respiratory organs that extract dissolved oxygen from water and release carbon dioxide.

  • Gonads: Reproductive organs (ovaries in females, testes in males) responsible for producing eggs or sperm.

  • Heart: A two-chambered organ that pumps blood through the fish's circulatory system.

  • Liver: An organ that aids in digestion by producing bile and stores energy in the form of fats and glycogen.

Fish Biology and Physiological Processes

• Skin and Scales: The skin provides a barrier against infection, while scales offer physical protection and reduce friction (drag) through the water.

• Muscles: Fish possess W-shaped muscle blocks called myomeres, which allow for the powerful lateral undulations needed for swimming.

• Digestion: The process involves the mouth, esophagus, stomach (where applicable), and intestines. Nutrients are absorbed to provide energy for growth and activity.

• Breathing: Involves the intake of water through the mouth, which is then forced over the gill filaments where gas exchange occurs via a counter-current system.

• Buoyancy: Regulated primarily by the swim bladder, which the fish can inflate or deflate to stay at a specific depth in the water column.

• Reproduction: Most bony fish practice external fertilization, spawning large numbers of eggs into the water to be fertilized by sperm.

• Senses: Fish utilize a combination of sight, smell (chemoreception), and the lateral line system to navigate, find food, and avoid predators.

The Process of Ageing Fish

• Method: The primary method for accurately ageing fish involves the examination of otoliths (ear stones).

• Process:

  1. The otoliths are extracted from the fish's head.

  2. The otolith is often embedded in resin and sliced into a very thin section.

  3. Under a microscope, scientists count the internal rings (annuli), similar to counting rings in a tree trunk.

  4. Each ring typically represents one year of growth, allowing researchers to determine the age of the fish and the health of the overall population structure.