Clupeids and stickleback biomass, fishery landings, and hydrographic variables from the Baltic Sea

Description of the data and file structure: data on fish biomass, fishery landings and hydrographic variables from the Baltic Sea. The data were used to explore the relationships between clupeids and three-spined stickleback, specifically whether reduced predation from herring and competition from both sprat and herring may have contributed to the recent increase of three-spined stickleback in the Baltic Sea.
The data is structured in six separate datasets. Each record report values of fish biomass or abiotic variables related to a specific ICES statistical rectangle (ca. 55 × 55 km size, corresponding to 0.5 degrees in latitude × 1 degree in longitude) and a specific year. The datasets can be merged using the field "year" and "ICES". The files have the following dimensions: ICES_Hydrographic_data_by_year.csv, 4465 rows × 20 columns; herring_biomass.csv, 2056 rows × 5 columns; landings_herring.csv, 2867 rows × 3 columns; landings_sprat.csv, 2108 rows × 3 columns; sprat_biomass.csv, 2042 rows × 4 columns; stic

数据与文件结构说明：本数据集涵盖波罗的海的鱼类生物量、渔业捕捞量与水文变量数据，旨在探究鲱形目鱼类与三刺棘鱼（three-spined stickleback）的种群关系，具体分析波罗的海近年三刺棘鱼种群数量上升是否与鲱鱼捕食压力降低，以及西鲱与鲱鱼带来的种间竞争缓解存在关联。
本数据集共包含6个独立子数据集，每条记录均对应特定的国际海洋考察理事会（International Council for the Exploration of the Sea，简称ICES）统计矩形（尺寸约为55×55公里，即纬度0.5°×经度1°）与指定年份的鱼类生物量或非生物变量数值。可通过"year"（年份）与"ICES"字段对各子数据集进行合并。
各数据文件的维度信息如下：
ICES_Hydrographic_data_by_year.csv：4465行 × 20列；
herring_biomass.csv：2056行 × 5列；
landings_herring.csv：2867行 × 3列；
landings_sprat.csv：2108行 × 3列；
sprat_biomass.csv：2042行 × 4列；
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