Fish Behavior 1

Eco-ethology

Jacques Brusle, Jean-Pierre Quignard

• Publisher: Wiley-ISTE
• Year: 2020
• Print ISBN: 9781786305367
• eBook ISBN: 9781119721925
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Fisheries & Aquaculture
• Index: Technology & Engineering

Advances in underwater exploration, in situ observation of fish populations, as well as the development of cutting-edge technologies, provide modern insights into behaviors and strategies of fish, whose cognitive abilities have long been underestimated and undervalued. Fish Behavior 1 presents current knowledge about fish biology, ecology and ethology. In light of the most recent scientific work, this book examines the habitats exploited by fish, as well as the strategies and tactics they have adopted regarding the occupation of available territories. It also addresses communication issues between individuals during social interactions. This book is intended for researchers, teachers, masters and doctoral students in biology and biogeography, engineers and technicians responsible for the development and protection of natural environments and public aquariums, in addition to aquaculturists, fishermen, environmentalists and ecologists.

1
Habitats: Occupation, Protection and Exploitation

1.1. Diverse and unusual habitats

A species can occupy the same habitat throughout its life, from the larval stage to adulthood (pelagic fish), but most species, after a planktonic larval stage (open water habitat), change habitat to live either near the seabed (benthonectonic and demersal species*¹) or in contact with the substrate or even buried in it (benthic species*). In addition, many species, depending on their life stages, choose temporary ecological niches that can be used for protection, feeding and reproduction and where intra- and interspecies competition may be less. Such a choice is often decisive in the survival of individuals and populations.

All aquatic ecosystems, and even some land-based habitats, have been used by fish populations, with few ecological niches deprived of their presence, as evidenced by the examples of fish colonizing many different types of habitats.

1.1.1. Psammophilous* habitats

The catfish Pygidianops amphioxus has the distinction of living constantly buried in the sandy substrate of the bed of Amazonian rivers since it has never been seen swimming in open water. More dependent on sediment than flatfish – sole, plaice, etc. – or than weevers, which are rather at the interface between sand and water and move above the seabed, feeding on the prey in this familiar environment: specifically, benthic insect larvae such as chironomids, as well as copepods that they absorb by suction through sedimentary particles. Its feeding activity is essentially nocturnal, like that of other catfish. But how does it reproduce? Is this way of life safe, as though burrowing predators were not able to detect its presence and capture it by digging it up?

Flatfish prefer sandy or gravel substrates of a specifically determined granular size* that provide them with camouflage sites in which to develop their mimicry skills (Volume 1, section 1.3.4). In addition, some species, such as American plaice Pseudopleuronectes americanus, use burial in the sediment (3, 6 or 9 cm deep) for the thermal regulation of their body: their internal temperature is higher than that of ambient water in winter and, conversely, lower in summer, with the sediment providing natural air conditioning.

Other nectobenthic species, although less dependent on sandy environments, have an imperative need to use such an environment, either to feed like the red mullet Mullus sp., or to reproduce like the Californian grunion Leurestes tenuis, or the Japanese fugu Takifugu sp.

Bibliography: Env.Biol.Fishes, 2014, 97: 59-68 & DOI:10.1007/s10641-013-0123-9, Mar.Ecol.Prog.Ser., 2019, 609: 179-186 & DOI.org/10.3354/meps123354

1.1.2. Reef cavity habitats

Reef corals create complex mineralized structures with an extreme diversity of habitats used by small fish whose size and morphology are perfectly adapted to the geometric structures created. The great diversity of coral structures, constituting a multitude of highly specialized microhabitats, makes it possible to shelter many small fish with highly diverse body shapes that use the structures as anti-predator refuges, food resources and egg spawning sites. On the Australian Great Barrier Reef, blennies such as the Salaria, Glyptoparus and others, all small fish particularly vulnerable to predators, must find safe havens, as species including snappers, groupers and morays are permanent threats. All cavities – holes, crevasses, drop-offs, caves – among Porites corals are therefore sought and occupied according to their diameter, depth and habitability, to within a few millimeters or a few centimeters, and affect all species in accordance with their own morphology, with precise interspecies differences reflecting a very specific division of habitats that promotes their coexistence. Competition for the occupation of the best shelters is generally fierce, and all species sometimes need to defend their personal habitat.

The gobies, Gobiodon histrio, live in close association with the coral reefs of the Red Sea, using microhabitats created by host corals according to the distance between Acropora branches and their own body morphology, in particular, their width, which allows them to creep into interbranchial spaces. Goby species with compressed bodies, laterally flattened, are favored in this interspecies competition and remain particularly faithful to their individual habitat. Described as cryptic*, they shelter in Acropora branches in accordance with their length and the interbranchial space of each branch, with lateral compression of the body and a small size ensuring a certain interspecies segregation. They jointly exploit coral architecture by adapting perfectly to its geometric constraints, with their maneuverability conditioning their protection and movement, and therefore their survival, and justifying their movement from branch to branch as they grow in order to continuously occupy “tailor-made” habitats.

The distribution of various species of damselfish, such as Dascyllus aruanus or Chromis viridis in Red Sea coral reefs, follows well-defined habitat rules reflecting the type of reef, continuous or sparse, and, especially, the specific morphology – size, volume, gill density – of the linked coral species, i.e. seven Acropora species. Similarly, Chrysiptera parasema prefers to use Acropora corals as a habitat-refuge, with 97% of juveniles associated with those corals. The density of its populations is closely correlated with that of the branchy corals of this species, which is particularly favorable to protection against predators. Reefs with wide coral cover support dense populations of these small fish, which are subject to very strong intraspecies competition for the occupation of secure habitats that provide valuable refuges and avoid overly exposed reef areas.

The distribution of butterfly fish, Chætodon sp., in New Caledonia, meets similar requirements for the availability of microhabitats in the coral ecosystem. This kind of individual selection of micro-habitats ensures that each resident is provided with food and, above all, security. The reduction in the coral coverage of more than 90% in some areas of the Great Barrier Reef, following coral bleaching, is seriously affecting populations of the various species of butterfly fish.

Naturally occupying the highly structured coral reef habitats, squirrel fish, Sargocentron microstoma, given their size and morphology and like many reef species, suffer severely from their...

Table of contents

• Cover
• Table of Contents
• Prefece
• Introduction
• 1 Habitats: Occupation, Protection and Exploitation
• 2 Strategies and Tactics for the Occupation of Available Territories
• 3 Communication and Social Life: Behaviors Related to Social Interrelations between Congeners, Parasites and Predators
• Glossary
• Species Index
• Summary of Volume 2
• End User License Agreement