FAA 306 — Fisheries Ecology: Lecture Note

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LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: FAA 306 Course title: Fisheries Ecology Course credit load: 2 Units Series 1: Principles of Ecology and Ecological Processes Part 1.1: Foundations of Ecology Sub Part 1.1.1: Definition and scope of ecology Sub Part 1.1.2: Principles of ecological organisation Sub Part 1.1.3: Importance of ecology in fisheries Part 1.2: Ecological Processes and Regulatory Factors Sub Part 1.2.1: Energy flow and nutrient cycling Sub Part 1.2.2: Primary production and regulatory factors Sub Part 1.2.3: Role of abiotic and biotic factors Part 1.3: Diversity and Abundance in Aquatic Systems Sub Part 1.3.1: Fish diversity and ecological niches Sub Part 1.3.2: Population dynamics and abundance Sub Part 1.3.3: Habitat selection and adaptation Part 1.4: Food Chains, Webs, and Trophic Relationships Sub Part 1.4.1: Structure of food chains and webs Sub Part 1.4.2: Trophic levels and energy transfer Sub Part 1.4.3: Implications for fisheries ecology Introduction

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Ecology provides the foundation for understanding how living organisms interact with one another and with their environment. In fisheries, these ecological principles are particularly important because they explain the processes that regulate fish diversity, abundance, and survival. By studying ecological processes, learners gain insight into how energy flows through aquatic systems, how nutrients are cycled, and how both biotic and abiotic factors shape the distribution of species. This Series sets the stage for the rest of the course by equipping you with the ecological knowledge needed to interpret fisheries systems in Nigeria and beyond. The aim of this Series is to introduce you to the fundamental principles of ecology and to explain the ecological processes that regulate fish populations and aquatic environments. It seeks to provide you with the skills to analyse ecological organisation, interpret diversity and abundance, and understand the role of food chains and webs in fisheries ecology. We shall commence this Series by examining the foundations of ecology, including its definition, scope, and importance in fisheries. Next, we will explore ecological processes and regulatory factors, focusing on energy flow, nutrient cycling, and the role of biotic and abiotic influences. Following that, we will study diversity and abundance in aquatic systems, considering fish populations, niches, and habitat selection. Finally, we will conclude by analysing food chains, webs, and trophic relationships, highlighting their implications for fisheries ecology. Series Learning Outcomes Upon completing this Series, you should be able to: SLO 1.1 define ecology and explain its scope in relation to fisheries (Linked to Part 1.1), SLO 1.2 describe the principles of ecological organisation and their relevance to aquatic systems (Linked to Part 1.1), SLO 1.3 explain the importance of ecology in fisheries management and resource sustainability (Linked to Part 1.1), SLO 1.4 analyse ecological processes such as energy flow and nutrient cycling in aquatic environments (Linked to Part 1.2), SLO 1.5 explain how primary production is regulated by abiotic and biotic factors (Linked to Part 1.2), SLO 1.6 describe the role of biotic and abiotic factors in shaping fish diversity and abundance (Linked to Part 1.2), SLO 1.7 identify patterns of fish diversity and ecological niches in aquatic systems (Linked to Part 1.3), SLO 1.8 analyse population dynamics and factors influencing fish abundance (Linked to Part 1.3),

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS SLO 1.9 explain habitat selection and adaptation strategies of fish species (Linked to Part 1.3), SLO 1.10 describe the structure of food chains and webs in aquatic ecosystems (Linked to Part 1.4), SLO 1.11 explain trophic levels and energy transfer in fisheries ecology (Linked to Part 1.4), and SLO 1.12 evaluate the implications of food chains and webs for fisheries management (Linked to Part 1.4). 1.1 Foundations Of Ecology 1.1.1 Definition and scope of ecology Ecology is the scientific study of how organisms interact with one another and with their physical environment. It examines relationships at different levels, from individuals and populations to communities and ecosystems. The scope of ecology in fisheries is broad, as it helps us understand how fish species survive, reproduce, and thrive in aquatic systems. By studying ecology, we can interpret patterns of distribution, abundance, and the factors that regulate aquatic life. Fill in the blank: Ecology is the scientific study of how organisms interact with one another and with their ______ environment.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1 Organism–environment interactions in ecology 1.1.2 Principles of ecological organisation Ecological organisation refers to the hierarchical structure of life within ecosystems. The main levels include individuals (single organisms), populations (groups of the same species), communities (different species living together), and ecosystems (communities interacting with their physical environment). Each level provides insights into how energy flows, how species interact, and how systems remain balanced. In fisheries, ecological organisation helps us analyse fish populations, their habitats, and the wider aquatic systems they depend on. Fill in the blank: The four main levels of ecological organisation are individuals, populations, communities, and ______. Level Description Individual A single organism of a species (e.g., one fish, one tree). Population A group of individuals of the same species living in a defined area. Community Different populations of species interacting within the same environment. Ecosystem Communities interacting with their physical environment (biotic + abiotic factors). Table 1.1 Levels of ecological organisation

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1.3 Importance of ecology in fisheries Ecology is important in fisheries because it provides the framework for managing aquatic resources sustainably. By applying ecological principles, managers can predict how fish populations respond to environmental changes, regulate fishing practices, and maintain biodiversity. For example, understanding food webs helps identify the impact of removing certain species, while knowledge of population dynamics guides decisions on fishing quotas. In Nigeria, ecological studies are essential for balancing artisanal and industrial fisheries, ensuring long-term productivity. Fill in the blank: Ecology helps fisheries managers regulate fishing practices and maintain ______. Key Point Explanation Sustainability Ecological knowledge ensures fishing practices maintain long-term stock health and resource availability. Biodiversity Protects diverse species and habitats, reducing risks of ecosystem imbalance. Regulation Provides the scientific basis for rules such as gear restrictions, closed seasons, and quotas. Productivity Healthy ecosystems support higher yields and stable fisheries, benefiting communities and economies. Resilience Understanding ecological interactions helps fisheries adapt to environmental changes and climate impacts. Box 1.1 Importance of ecology in fisheries Pilot questions 1.1 Define ecology and explain its scope in fisheries. List the four main levels of ecological organisation. State one reason why ecology is important in fisheries management. Give one example of how ecological knowledge can guide fishing practices. Explain how ecological organisation helps in analysing fish populations.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.2 Ecological Processes And Regulatory Factors 1.2.1 Energy flow and nutrient cycling Energy flow refers to the movement of energy through an ecosystem, beginning with producers such as algae and aquatic plants, which capture solar energy through photosynthesis. This energy is then transferred to consumers like herbivorous and carnivorous fish, and finally to decomposers that recycle nutrients back into the system. Nutrient cycling is the continuous movement of essential elements such as carbon, nitrogen, and phosphorus within ecosystems. Together, energy flow and nutrient cycling maintain balance and productivity in aquatic environments. Fill in the blank: Energy flow begins with producers such as ______ and aquatic plants. Figure 1.2 Energy flow and nutrient cycling in aquatic ecosystems 1.2.2 Primary production and regulatory factors Primary production is the rate at which producers, mainly algae and aquatic plants, convert solar energy into organic matter. This process forms the basis of aquatic food webs. Regulatory factors include abiotic factors such as light, temperature, and nutrient availability, and biotic factors such as grazing pressure from herbivores. When conditions are optimal, primary production increases, supporting higher fish abundance. Conversely, poor conditions can limit productivity and reduce fish populations.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: Primary production is the rate at which producers convert ______ energy into organic matter. Plate 1.1 Algal growth as primary production 1.2.3 Role of abiotic and biotic factors Abiotic factors are non-living components of the environment, such as water temperature, salinity, pH, and dissolved oxygen, which directly influence fish survival and distribution. Biotic factors are living components, including predators, competitors, and prey species, which shape ecological interactions. Both sets of factors work together to regulate fish diversity and abundance. For example, low oxygen levels may limit fish populations, while high predation pressure can reduce abundance even in favourable physical conditions. Fill in the blank: Temperature, salinity, and dissolved oxygen are examples of ______ factors. Factor Type Examples Explanation Abiotic Temperature, salinity, oxygen Physical and chemical conditions that influence fish survival, growth, and distribution. Abiotic Light, nutrients, pH Affect primary productivity and habitat suitability for aquatic organisms.

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