Advancing presence and changes in body size of brown shrimp Crangon crangon on intertidal flats in the western Dutch Wadden Sea, 1984–2018

Abstract

Upon settlement after a pelagic larval phase, brown shrimp Crangon crangon depend on intertidal flats. During low as well as high tide the young brown shrimp play roles as predators of meiofauna and as prey for fish and birds. Unlike the biology of the commercially important adults, knowledge on these juveniles remains sketchy. Here we provide an analysis of 35 years of brown shrimp monitoring in May-June on intertidal flats in the westernmost Dutch Wadden Sea. Intertidal shrimp densities were sampled bi-weekly at three stations during low tide, using sampling corers. We show that over this 35-year period the appearance of shrimp on mudflats advanced by 12 days (− 0.34 days yr −1 ). Simultaneously, densities on 7 May increased by more than 2.4 times, from 28 shrimp m −2 in 1984 to 69 shrimp m −2 in 2018. Across years, mean shrimp length decreased from 12.6 to 10.7 mm, but length in early May did not change. The advancement in settlement and the increasing shrimp densities correlated with increases in the seawater temperatures in April more than during earlier times of the year. We propose four interpretations of these changes: (1) shrimp settle on the mudflat when they reach a certain 'threshold' length, (2) settlement of shrimp is controlled by a critical period of 'threshold' temperature sensitivity, (3) timing of shrimp settlement is a response to food availability on mudflats or (4) a direct response to inferred predation pressure. The different interpretations will lead to different scenarios of change in a warming world.

Sanderlings Feed on a Diverse Spectrum of Prey Worldwide but Primarily Rely on Brown Shrimp in the Wadden Sea

“…Over the past decades, shrimp have become more abundant during the spring staging period of Sanderlings (May) in the Wadden Sea (Penning et al 2021). It is unknown whether the availability of shrimp has also increased during the autumn staging period.…”

Density distribution of Penaeus merguensis De Man, 1888 based on habitat in the waters of Merauke District, South Papua Province, Indonesia

“…That shows the higher the turbidity value, the more the density of banana prawns increases (Silaen and Mulya 2018), suggesting that P. merguensis requires a high turbidity level and is caught with higher density in areas with high turbidity (Vance and Rothlisberg 2020;Widiani et al (2021). This can be explained by the fact that increased turbidity will provide protection from predators and make it easier for banana prawns to find food in the form of mollusks that immerse themselves in mud (Sreekanth et al 2019;Hasidu et al 2020;Penning et al 2021;Taylor et al 2017b). In addition, the possibility of prawns movement as in salinity patterns, following the level of turbidity; especially prawns caught are adult prawns with increasingly extensive food and are widely available in waters with high turbidity levels (Silaen and Mulya 2018;Lorencová and Horsák 2019).…”

Exploration in red knots

“…Faster exploring red knots mainly eat higher quality soft prey and have smaller gizzard muscles (Chapter 2, Bijleveld et al, 2014). However, soft prey such as shrimp is available in the mudflats of the Wadden Sea only during summer months and completely disappears in October ( van Gils et al, 2005b;Penning et al, 2021). After summer, faster exploring red knots may therefore completely switch to hard-shelled prey or leave the Wadden Sea area to search for soft prey somewhere else.…”