Condition-dependent skipped spawning in anadromous brown trout (Salmo trutta)

Repeat spawners of anadromous salmonids may contribute significantly to population resilience by providing multiple cohorts to both seawater and freshwater life stages. In this study, winter survival of sea trout (Salmo trutta Linnaeus, 1758) post spawners (kelts) was 89%. Sea survival increased linearly with female length with a return probability between 30% and 50%, whereas males attained a maximum return probability of 60% at 520 mm. Of the returning sea trout, 40% skipped spawning and they had significantly lower condition factor as kelts compared with those who returned after one summer. These results suggest that sex-specific differences in individual post-spawning growth–survival trade-off exist and that energetic status of descending kelts may influence the probability to skip spawning. We discuss to what extent hydropower may reduce post-spawning survival due to blocking of river descent opportunities, potentially altering the fitness landscape and favouring new life-history adaptations. From a management perspective, it is concluded that it is crucial to maintain connectivity in regulated rivers, allowing fish to complete repetitive spawning and feeding migrations, thus contributing to population productivity.

ANALISIS EFEKTIVITAS PROGRAM PELATIHAN SEA SURVIVAL PADA PT. BUMI LIPUTAN PUSAKA, BALIKPAPAN � KALIMANTAN TIMUR

Skripsi ini membahas tentang analisa efektivitas pelatihan yang di selenggarakan oleh PT. Bumi Liputan Pusaka. Metode yang digunakan dalam penelitian ini adalah CIPP (Context, Input, Proces, Product), merupakan penilitian kualitatif deskriptif atau observatif. Hasil penelitian ini memberikan gambaran tingkat efektivitas penyerapan materi pelatihan Sea Survival, dimana indikator efektivitas dapat dilihat melalui empat komponen, 1). komponen konteks yang berisi data diri, 2). komponen input yang terbagi atas komponen internal dan pretest, 3). komponen proses yang berisi evaluasi dari pelatih dan 4). komponen produk yang berisi hasil pretest Selain itu diberikan rekomendasi � rekomendasi sebagai bahan untuk perusahaan melakukan perbaikan agar efektivitas penyerapan materi pelatihan dapat di implementasikan.

Sea-to-sea survival of late-run adult steelhead (Oncorhynchus mykiss) from the Columbia and Snake rivers

We used biotelemetry and genetic stock identification to assess sea-to-sea survival and run composition of 1212 late-migrating adult steelhead (anadromous Oncorhynchus mykiss) through the Columbia River and Snake River migratory corridors. The late run was predominated by steelhead from Idaho’s Clearwater and Salmon rivers that must pass eight large hydroelectric dams during both prespawn and postspawn migrations. In 2 years (2013 and 2014), prespawn survival to Snake River tributaries (>500 km) was 0.48–0.67 for the most abundant populations and was higher for females and 1-sea fish (i.e., fish that spend one winter at sea). Annual survival from Snake River tributary entry to postspawn kelt status was 0.14–0.17, with higher survival for females and those without hatchery fin clips. Kelt outmigration survival was 0.31–0.39 past four Snake River dams and 0.13–0.20 past all eight dams and was highest for smaller kelts. Full-cycle adult freshwater survival (sea-to-sea) including 16 dam passage events was 0.01–0.02. Younger steelhead and those without fin clips survived at the highest rates. This study uniquely partitioned mortality across prespawn, reproductive, and kelt life history stages and informs management strategies for this conservation-priority metapopulation.

Effects of muscle lipid concentration on wild and hatchery brown trout (Salmo trutta) smolt migration

Annually, hatchery programs are releasing millions of salmonid smolts into the Baltic Sea. Recent estimations indicate a decline in smolt sea survival, questioning the ecological and socioeconomic values of these programs. Concurrently, hatchery smolts have increased in lipid concentration. Salmonids display partial migration, and it is suggested that the ratio of migrants/residents is affected by individual smolt energetic status. To test whether the increased energetic status of hatchery smolts could explain the noted decrease in survival, we released wild trout smolts, conventional hatchery smolts, and hatchery smolts of low energetic status into a Baltic Sea river. Using telemetry, we obtained data on the number of successful migrants, their swimming speed, and diel migratory behaviour. A much lower proportion of conventional smolts (30%) successfully migrated to the coast. No difference was found between wild (74%) and hatchery smolts of low energetic status (64%). Furthermore, conventional smolts migrated slower and showed no diel migratory pattern. The results are of high relevance for hatchery programs producing partially migrating fish.