Home ranges - Agonistic interactions of Fishes

Home ranges

Territories are usually a spatial subset of the larger area that a fish uses in its daily activities. Such home ranges or activity spaces are common in fishes, which move over the same parts of the habitat at fairly predictable intervals, often daily but also at other timescales (Lowe & Bray 2006). Home range is dependent on fish size and species. Larger species and individuals generally move over larger ranges, although range size may decrease with growth in an individual (e.g., Bocaccio Rockfish, Sebastes paucispinis, Starr et al. 2002; Greasy Grouper, Epinephelus tauvina, Kaunda- Arara & Rose 2004). Home range may be very restricted, as in the few square meters around a coral head (e.g., gobies, damselfishes) or contained in a tide pool (e.g., pricklebacks) (Sale 1971; Horn & Gibson 1988; Kroon et al. 2000). Some benthic stream fishes may have ranges of 50–

100 m2 (Hill & Grossman 1987) whereas others may range over hundreds of meters (e.g., Albanese et al. 2004). Intermediate ranges of a few hundred square meters characterize many lake, riverine, kelpbed, and reef species, although many large coral reef fishes are relatively sedentary, utilizing concentrated reef resources. Home ranges of many large species such as groupers and snappers may not exceed 0.1 km2 (Pittman & McAlpine 2003). Pelagic predators such as tunas, salmons, large sharks, and billfishes cross entire oceans seasonally or repeatedly. But even these oceanic wanderers show evidence of periodic residence in certain areas on a seasonal basis (see  Annual and supra-annual patterns: migrations).

Although a fish may spend 90% of its time each day within its home range, it is common to encounter individuals many meters or even kilometers away from their usual activity space. Such movements characterize fishes in most habitats (e.g., Fausch et al. 2002). These periodic excursions imply a well-developed homing ability in many species. Numerous studies, involving experimental displacements of tagged individuals, have repeatedly shown a strong tendency to return to home sites in many fishes. The Tidepool Sculpin, Oligocottus maculosus, can be displaced as far as 100 m from its home tide pool and will find its way back, using either visual or chemical cues. Older fish can still remember the way home after 6 months in captivity. Younger fish have shorter memory spans and require both visual and chemical cues to find home successfully, whereas older individuals do not require both types of information (Horn & Gibson 1988). In some species, adults find their way around the home range by identifying landmarks, creating a cognitive map of the locale (Reese 1989). In general, older fish have a stronger homing tendency and often occupy smaller home ranges than younger individuals. Since juveniles are the colonists that most often invade recently vacated or newly created habitat, this generalization is not surprising (Gibson 1993).

The use of a home range is affected by several components of a fish’s biology. Normal ranges are often deserted during the breeding season. This may involve no more than a female damselfish having to leave her territory to lay eggs in the adjacent territory of a male, but can also involve long-distance movements of 100 km or more to traditional group-spawning areas, such as occurs in many seabasses on coral reefs. Colorado Pikeminnows, Ptychocheilus Lucius (Cyprinidae), make annual round-trip movements of as much as 400 km between traditional spawning and normal home range areas. The home range also interacts with shoaling behavior in some species and can differ among individuals within a species. Yellow Perch, Perca flavescens, form loose shoals (see next section) of many individuals that forage in the shallow regions of North American lakes. Home range size is directly correlated with the amount of time individuals spend in shoals. Individuals with strong shoaling tendencies also have larger home ranges. As a shoal enters the residence area of an individual, the resident fish joins the shoal until the shoal moves to the boundary of the home range. Home ranges and fi delity to particular sites have probably arisen because intimate knowledge of an area increases an individual’s ability to relocate productive feeding areas or effective refuge and resting sites, reducing the amount of energy expended and risk incurred while searching for such locales (Helfman 1984; Tyus 1985; Shapiro et al. 1993).

Knowledge of home range size has important implications for fish conservation, especially with regard to the creation of reserves and protected areas. Reserves must be large enough to encompass the home ranges of both sed entary and mobile species; without specific knowledge of daily, seasonal, and ontogenetic movements, a reserve might fail to encompass the range of habitats or the actual areal expanse needed to protect most species and most life history stages (Kramer & Chapman 1999; Cooke et al. 2005; Sale et al. 2005). The likelihood of spillover of individuals into adjacent areas, an anticipated benefit of reserve creation, also depends on movement and will vary in relation to reserve design and species behavior. Relationships between home range size and reserve design have been examined in tropical and temperate locales involving taxa as diverse as seabasses, sparids, goatfishes, wrasses, and surgeonfishes, to name a few (Meyer et al. 2000; Egli & Babcock 2004; Meyer & Holland 2005; Popple & Hunte 2005; Topping et al. 2005).