Assessment of a brown troutSalmo truttapopulation in the River Gallo (central Spain): Angling effects and management implications (Salmonidae)

Abstract

The brown trout population of the River Gallo (central Spain) was monitored every two months during 1996 to determine the current impact of angling. To evaluate the influence of additional parameters, physical habitat and food availability were also studied. To assess fishing pressure, trout harvest and angling exploitation, a partial creel census was conducted during the 1996 fishing season. Differences were found in densities and biomass between exploited (1182.4 fish ha -1 , 68.3 kg ha -1 ) and unexploited areas, the latter being markedly higher (3135.1 fish ha -1 , 208.2 kg ha -1 ). Production was quite superior in the unexploited area and decreased (from 144.5 kg ha -1 yr -1 to 37.2 kg ha -1 yr -1 ) as fishing pressure increased. However, no consistent differences were observed in growth, condition factor, age diversity, mortality, recruitment age and turnover ratio. Sport fishing seems to be the main negative factor influencing the balance within population of brown trout in the River Gallo and therefore management should be focused on more restrictive angling measures.

Decline in angler use despite increased catch rates: Anglers’ response to the implementation of a total catch-and-release regulation

“…Indeed, this was reported in several empirical studies (e.g., Anderson and Nehring, 1984;Novinger, 1987;Cornelius and Margenau, 1999;Newman and Hoff, 2000). However, other studies have found that total catch-and-release regulations or more stringent size or daily bag limits may result in reduced angler effort despite similar or increased catch rates (e.g., Muoneke, 1994;Almodóvar and Nicola, 1998;Boxrucker, 2002;Hurley and Jackson, 2002;Parker et al, 2007). Similarly, restrictive fly-only regulations that prohibited the use of organic bait were also been found to reduce angling pressure on a trout stream (Shetter and Alexander, 1962).…”

Reproductive traits of stream‐dwelling brown trout Salmo trutta in contrasting neighbouring rivers of central Spain

“…After maturity, somatic growth ceases, as has been described for many salmonid populations (Jonsson, 1985; Myers et al ., 1986). Fishing pressure in these populations is high and decreases the longevity of the fish (Almodóvar & Nicola, 1998; Almodóvar, Nicola & Suárez, 2002). There is probably a relationship between maturation and longevity, because a short life span selects for maturity at a young age, as documented by Haugen (2000) for exploited grayling ( Thymallus thymallus L.).…”

Interactive effects of cover and hydraulics on brown trout habitat selection patterns

“…Consequently, the knowledge of the habitat requirements of species is essential for assessing different impacts from human activities on fish communities. This is especially relevant in salmonid wild populations of south European countries which are currently threatened by habitat destruction, pollution, introduction of exotic especies, overfishing and introgression of foreign genes as a result of artificial stocking (Almodóvar and Nicola, 1998Almodóvar et al, 2001Almodóvar et al, , 2002Almodóvar et al, , 2006aElvira and Almodóvar, 2001).…”