**7. References**

348 Modern Telemetry

in the interpretation of data, since a low proportion of area (eight panel antennae) was sampled for every diel cycle. This limitation was reported in several studies using PIT telemetry technology and further improvements are needed to increase the detection range of PIT reading units. With regard to the experimental design of this study, protocols combining a superior number of stationary flat-bed antennas and MPD units covering, at the same time period, the entire stream reach selected, and the use of portable antenna technology will improve the quality of data acquisition related to the small-scale movements

The combination of the different methodologies used, *i.e.* radio and PIT-telemetry, allowed a better understanding of the movement patterns and spatial distribution of stocked and native trout through intensive tracking of a small number of radio-tagged fish over a short time scale and continuous monitoring of movements and microhabitat use by PIT-telemetry. As pointed out by Ovidio et al. (2009) gaps in the fish behaviour can be closed using complementary methodologies. This study also confirmed previous observations following distinct methodologies (*e.g.* snorkelling, electrofishing), which detected, just one month after, a low proportion of stocked brown trout in the stream segment where they had been released (Cortes et al., 1996; Teixeira et al., 2006). The potential negative impacts of stocking on wild population seemed to be limited in time and space and were demonstrated by the monitoring of fish movement (*e.g.* radiotelemetry), since a high dispersion was registered, mainly in downstream direction, of the majority of stocked fish. The rapid decrease of stocked fish condition, the variation of hydrological parameters and the vulnerability to predation were factors that contributed to the low efficiency of the stocking programs. For these reasons, stocking of brown trout as a management tool for supplementing the recreational fisheries in rivers must be questioned based on the reduced adaptation of stocked trout to wild environment. However, in specific conditions it could be a costeffective option, namely if catchable-size trout were used and applied to selected areas where angling pressure is intense. It is possible that a greater proportion of stocked trout never adopt the adequate behaviour that normally is displayed by native trout. Probably the minor adaptation of hatchery-reared fish to the wild environment is more visible when stocking is made recurring to fish of superior size/age (> 1+). Although Pedersen et al. (2003) had found a higher survival and adaptation of smaller brown trout (0+) over a period of 11 months, a longer time is needed to fish reach the legal catch size for anglers and, as referred by Aarestrup et al. (2005), stocking with trout over the legal size limit could be the correct management tool for supplementing the recreational fisheries. Finally, it is important to consider alternative management techniques with low ecological risks like the improvement of the fish habitat and protective measures (*e.g.* catch-and-release, better management and angling regulations), to promote a superior biogenic capacity of the aquatic system and assure the conservation and/or exploitation of self-sustainability of wild

We wish to thank Ângelo Saraiva, Tiago Martins and Paula Escalda for their field assistance. Thanks also to Rogério Rodrigues, Graça Barreira, Julieta Sampaio and Augusto Maia from

by sympatric stocked and native trout populations.

**5. Conclusion** 

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**6. Aknowledgments** 


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**1. Introduction 1.1 Definition** 

ecology.

populations.

**1.2 Importance to sea turtle researches** 

**1.2.1 Life history trait studies** 

**17**

I-Jiunn Cheng

*Institute of Marine Biology,* 

*Republic of China (ROC)* 

**Sea Turtle Research** 

*National Taiwan Ocean University, Keelung, Taiwan* 

Telemetry includes an array of techniques that allow remote monitoring, measurement and recording or reporting of information. It was first used in weather research and has expanded quickly to other disciplines. Relatively accurate measurements without direct observer participation allow some important research that was impossible to conduct in the past. This has an important implication for study of life history traits of species that migrates long-distances, such as sea turtles. The ocean habitat, wide distribution ranges and movement across political boundaries all create difficulties for direct study of sea turtle behavior. Telemetry can overcome these obstacles and is a cost-effect tool for behavioral

Animal migrations, especially long-distance movements, are to explore for resources across substantial temporal and spatial scales. They are often adaptations for avoiding seasonal depletion of local resources in order to survive and reproduce in suitable environments (Alerstan et al., 2003; Southwood and Avens, 2010). Sea turtle hatchlings, because of high predation pressure in nearshore waters and otherwise unsuitable habitats near nesting beaches, must migrate (actually they must "drift") after leaving their nests to suitable nursery grounds (Bolten, 2003). In addition, sea turtles evolved from freshwater turtles (Pritchard, 1997). Thus, even though these giant reptiles have successfully invaded the ocean, they must still return to their natal beaches to nest (called "natal homing"; Carr, 1967). Therefore, migrations play substantial roles in the survival of sea turtle

Sea turtles are ocean-wide, long-distance migrating reptiles that spend more than 95% of their time at sea. Except for leatherbacks, olive ridleys, flatbacks and some loggerheads, hatchlings spend their early lives drifting in the ocean (often referred to as "the lost years"; e.g. Bolten, 2003; Carr, 1967). After 5 to 7 years in the open ocean, they migrate into foodrich nearshore waters and feed along the bottom (Carr, 1967; Plotkin, 2003). Some food-rich areas, such as coral reefs, seagrass beds and nearshore fishing grounds are the sites favorable for juvenile sea turtles (e.g. Hawkes et al., 2006). Due to the developmental shift in nutrient requirements and other needed conditions for growth, sea turtles often exhibit an

